Our Ideal combi which was fitted in Oct 2015 is still going strong, has only needed its annual service and clean out so far.

As i said before, if it packed up now it will have more than paid for itself in reduced bills, and we would happily have the same again.

Just looked at the paperwork, apparently its running 20kw on heating and 24kw for hot water, it has no trouble keeping up with the shower.

I'm really grateful for the additional info promptly offered .... muchappreciated.

The Grant name is one I only very recently started to hear. Further reading inspired there.

My aversion to Viessmann for the reasons noted earlier is further reinforced by the comments here... the problem with the HEX is noted with much interest given that it's the presence of a stainless HEX that would have been of most interest.

I still keep seeing people say that that Worcester and Vaillant are the BMW or Mercedes of the boiler world but I also keep seeing that they have their problems and their detractors.

Again I say ta for the extra food for thought.

I suspect some plumbers don't like Worcester Bosch boilers precisely because they are the most reliable on the market - less work for them down the road. Just like some mechanics and the most reliable Japanese cars, like Toyotas - aside from normal servicing and occasional wear and tear replacements, not much interesting (and financially lucrative) work to do.

And with the boilers, unlike with cars, plumbers have to compete on price for servicing, because most plumbers are trained up on servicing most boiler makes and units.

The problem with the Viessmann boilers is more about a general lack of skills amongst plumbers to install and maintain them correctly - yes, all makes will suffer from some degree of in-warranty failures, but sometimes certain components fail becuase they were installed incorrectly (not saying yours was), as some of my neighbours have been recently finding out.

Taking reliability and plumber expertise into account, I'd rank my list in this order for gas-fired domestic boilers:

Worcester Bosch;

Vaillant;

Viessman;

Ideal. Note that Ideal have recently taken over Keston, though I'm not a fan of theirs, especially when I found out of (IMHO) serious, safety-related design flaws in some of their boilers, particularly the ones that replace my (near end-of-life) Range Powermax twin flue boiler on a like-for-like basis.

The best thing for getting good service from a boiler is being able to find a really decent quality and honest plumber. Local independents are far better than most of those solely working for the Utility firms (especially as many of them can only select from a limited number of makes of boiler).

"They made lots of visits to try and fix and then seemed to run out of new parts to try as well as new ideas."

Outrageous. My understanding is that this is one of the most common causes of breakdown, and it is the result of incompetent installation. A wide diameter condensate pipe must be used if it goes directly out of the building and is therefore exposed to frost. Lagging is a less-than-elegant fix.

When our boiler was replaced (with a Vaillant) a few years back, I insisted the (narrow) drain pipe ran internally to join the waste from the downstairs loo's washbasin.

Another common problem with main-pressurised systems is that the expansion chamber within the boiler case is simply too small (and therefore has to work too hard) to cope; when ours failed, we were advised to fit a separate expansion vessel near the boiler, which fortunately is in the garage, with plenty of room.

Edited by FP on 07/04/2019 at 12:02

Re. "Grant" boilers (as mentioned by Avant), it seems they specialise in oil ... I have gas.

Another vote for WB. Ours is a regular boiler fitted in 2010 when the scrappage scheme was running. Apart from a service (by the local chap who fitted it) at about 18 month intervals it hasn't required attention. If it was to go wrong I'm pretty sure spares would be easy to get and any fitter would know how to fix it - a bit like a Ford Focus.

I would've had Vaillant as my top selection had their reliability not dropped over the past few years - they used to be as good as Worcester Bosch and were more liked by plumbers because they were easier to install and maintain - as well as simpler to use than the WBs. I always specified them for housing projects for that reason.

Admitedly I haven't done one of those projects for about 5 years now, hence why I was saddened to find out Vaillant had been suffering quality issues of late. They are still better than the mid-table brands, but not as good as WB. My experience with Viessmann has really only been on the larger commercial side - good quality, not much expertise on installations around, quite expensive and not as user-friendly as other makes. I assumed (including from my own research) that they would be similar on the domestic side.

Normally if a make will give long warranties (some of these 8-10 years if you use an accredited plumberr, not sure if the HX is included for quite that long) that normally means it'll be decent. Like with cars, increasingly the problems are electronics-related.

My heating engineer is advising installing a Worcester combi but installing a hot tank with the system to run 2 showers. Has anyone have any experience of such a system?

Yes, I had a Viessmann combi which ran the shower and basin in our loft conversion from the combi domestic hot water outlet. It also fed a small high heat recovery cylinder for water storage for the main shower, basin, kitchen utility etc. We simply teed off the heating flow and return directly below the boiler and treated the cylinder as another radiator effectively. We also put in a separate time clock for the small cylinder with a motorised valve operated through a cylinder thermostat. This would bring on the boiler to heat the cylinder separately from the heating. In summer for instance where we needed hot water storage but not heating. The house radiators had their own time clock, motorised valve and room thermostat. Both could be on at once or separately for convenience. Takes a bit of wiring with a 10 way junction box but quite simple really. Worked a treat for the 10 years before we moved and still going strong I would imagine.

Cheers Concrete

My heating engineer is advising installing a Worcester combi but installing a hot tank with the system to run 2 showers. Has anyone have any experience of such a system?

Technically, some high output combis can be used on their own (without any other cylinders) to provide enough DHW for 2 showers - they use one or two small thermal storage cylinders strapped to the back of the boiler, acting in a similar capacity to the 80L thermal store on my 'old' Powermax boiler.

Trouble is, the DHW output barely covers two showers, which means anyone using hot water elsewhere (sink, WHB or washing machine), or if at least one of the showers is a high output 'drench' shower (anything higher the 9L/min), then it won't be enough.

When I was specifiying combi boilers for homes, I always went one unit up the range more than the manufacturer recommended (where possible), so that there was always sufficient DHW for the whole property. Unfortunately, most modern properties are not large enough to accommodate a boiler+cylinder (especially a larger HW cylinder), thanks to our architect 'friends' and the developers.

Developers/builders tend to want boilers/heating systems that are cheap/easy to install, although because of the NHBD warranty, poor quality boilers will push them towards other designs.

In some very hard water areas, I suspect they've got the message that installing combis + cheesy in-line limefighters (useless) are not a viable design, and the vast majority of electromagnetic water conditioners are no good either (the few decent ones, especially the Hydromag unit, are expensive). As such, many combi boilers' heat exchangers (HX) were terminally scaling up in a year or two, sometimes less.

The problem often comes as the architects are under significant pressure to reduce costs by making homes smaller, meaning that the boiler+cylinder solution is not favoured by them, plus they are a bit less energy efficient (not that much, especially when the energy used/cost of repairs or use of EM water conditioners are factored in).

It is not helped by the modern use (more energy efficiency regs) of heat recovery ventilation systems for homes, which require ducting routed via ceiling voids, which often requires them to be larger to accommodate pipework and boiler flue crossovers. Architects want to reduce the height of these voids.

Potterton haven't had a great reliability record, and mistakenly bought the rights to the Range Powermax boiler I use, which is a good design in principle (not a condensing boiler, so no condensate drain, provides the same DHW output as a 28kW standard combi using a 14kW burner, no remote HW tank) but badly executed, hence why they aren't reliable.

Plumbers avoid them as they are very fiddly and require specific training to enable them to work on them (bad servicing was the reason why the government changed the law so that all flues run in voids need to have access panels to inspect them). They kept the Powermax name but changed the design for the follow-up model, which in my view wasn't a great deal better (essentially its a boiler+cyliner in one box) in terms of reliability.

Their sister company Baxi are better, but IMHO they are still middle of the road at best. But as before, the quality of your plumber makes the most difference as to how long a heating system/boiler lasts.

I am, without doubt, the world's worst decision maker.

I still haven't swapped my boiler.

Although, the fact that my 23 year old Ideal Classc FanFare 250 boiler with a cast iron heat exchanger is still working OK does mean I have time on my side. Everyone tells me it was Ideal's most reliable boiler and that I'm honoured to possess such a classic, vintage item.

To be honest, the money you save per year from having a new, more efficient boiler installed is nothing compared to the cost of the installation, even for a 25 year old boiler, as long as its reasonably reliable, the price of replacement parts are still reasonable (especially compared to new boilers' parts), reasonably plentiful and there are enough local plumbers willing and able to maintain them.

I worked out that replacing my 16+ yo non-condensing boiler (about 84% efficient) with a new, 90% efficient condensing boiler would save me about £100pa in bills. The cheapest new system installation would come out around the £2k mark, and the best (the one I'd want, including siting the new boiler in the same location as the existing one) would cost me at least another £500 on top of that.

Most decent quality condensing boilers last between 15 and 20 years, perhaps 25 if you're really lucky (better if you live in a soft water area). My boiler is an unusual one and thus this time is rapidly approaching replacement time (probably 2-3 years away at most) due to the above criteria. Yours maybe still able to last longer - some simpler older (non-combi) boilers can, if well maintained, last 25, 30 or even 35 years with a fair wind, especially if they are from a make still around.

Yes, you're 100% right.

Essentially I was just, initially, doing my homework so that if it did pack up in a manner that dictated end of life I would be able to go straight to the replacement item and go ahead without delay. It's had a few, fairly common but reasonably pricey bits and it might not need anything else for some time but as time has gone on I've almost talked myself into wanting a replacement. Daft innit :-)

My advice generally, and it applies just was well to keeping cars over 10 years old and (to some extent) household white goods, TVs, etc is to:

1. Do your homework to find a suitable replacement (or at least a shortlist to cover most eventualities) in advance of it going wrong, just in case the problem is terminal for the reasons previously described. Do the same to check if parts are still available and reasonably priced.

Plumbers tend to source them from local wholesalers because its easy and convenient, however the Interweb has a good number of other parts suppliers who can often offer lower prices or have the stock you need and can courier it to your home/workplace for a reasonable price. Many plumbers won't put in the work required to do this, though occasionally some really good ones will.

To be fair, it doesn't take 5 mins of looking, but neither does it take several hours. I found the OEM expansion vessel for my installation, which saved me a LOT of money, especially as my plumber didn't have to modify the pipe connection to install another brand.

Update this research once a year or more often for less reliable boilers, in case better units come along or others are superseded/have issues. This shouldn't take long to check new boilers on the market - they don't appear that often, not from the quality brands anyway.

Whenever you do get a problem with your old boiler or need it serviced, get quotes from a reasonable number of decent local plumbers, as I found with mine that the number who were trained to maintain it suddenly dropped from about 3-4 to just a couple.

2. Relying on one plumber who's trained to maintain a specific boiler/make (often that has gone out of business or the boiler is unusual) can be a real pain, even if they are a good plumber, as they may be so busy that you may be without heat and hot water for days. This is especially difficult in winter, when problems are far more likely to strike and this they are much busier anyway.

3. If changing boilers has to necessitate a change in the heating system configuration, e.g. (as mine will) installing a condensate drain (convenient drain point/route needed and/or power for an extra pump), a concentric flue/additional pipework is needed (perhaps a dropped ceing/bulkhead may be required) or new flue discharge is required, ask your normal plumber to provide a quote (even a rogh one will be useful) to get a reasonable estimate of the cost, which can easily land you with £500 - £1000 of extra costs.

Better to know well in advance to ensure the expertise, equipment and money's there specifically for it should the need arise.

Indeed - a heat-only gas boiler is the simplest type of the three. The good thing is that they are stil very popular, given how many homes over 25 years old there are that already have that system in place. I'd probably still go for one of the makes I will be for a combi that I previously mentioned, but the less complex nature of the heat only boiler perhaps gives you more options. Especially if there are other things to factor in like size restrictions.

One thing that's worth checking on, assuming you're not replacing the heating circulator pump (or going to on a like-for-like basis), is that any replacement boiler is reasonably designed for the heating flow and return temperature of your system.

Some Euro makes, and more and more UK ones, now base their boiler design on a flow and return temperature of 80degC flow, 60degC return, and not the old British way of 82/71. Almost of all of them can adapt to the higher flow temperature, but the smaller temperature difference can, on some models make a significant different to the heating water pressure drop through the boiler, because the pipes are smaller because they are designed for a 20degC drop rather than an 11degC drop.

Similarly, the existing radiators could, if you changed from an 82/71 system to an 80/60 system, be undersized if the pump output cannot be increased sufficiently (by turning it up from setting 1 to 2 or suchlike) to compensate for the additional water flow and (thus) system pressure drop required.

Just make sure whatever one you choose can cope with running on the old system, unless of course you would want to change many (or even all) of the radiators and the pump.

Just had a quote to supply & fit a new Worcester Greenstar 8000 35kw system boiler.

Including all new wireless controls and removal of the old boiler the cost is approx. £3,200 (power-flush an extra £580 - I have 19 radiators, it's a big old draughty Victorian semi.)!

He is a local independent Worcester accredited plumber (35 years experience) and I get a 10 yr warranty on everything supplied.

Only thing to remain from existing system will be the hot water tank, radiators / pipework.

I'm still waiting for other quotes so no idea if this is competitive or not yet. The boiler can be brought on-line for about £1,400. I have no idea how much the additional items cost (controls and Worcester magnetic filter, etc. - needed for 10yr warranty)

Thoughts please on this price?

New Worcester 35kw system boiler installed earlier this week with no dramas thus far. As the new boiler works on a sealed set-up, our central heating cold water storage tank is history, (as is the pump which is integral to the new boiler).

Had a minor but irritating issue with Worcester technical service/help, (not the fault of the plumber), as a small part which is shown in the technical literature as included is actually not supplied and is a £9 extra, (I would suggest this is a "bean-counter" issue)?

Extremely happy with the performance thus far. I know its still technically summer, but on a test run, the kitchen radiator (which used to take an age to get just luke-warm), is now very hot after only 10 minutes. Boiler is practically silent in operation and has a 10 year warranty.

I'll monitor gas use over the next 12 months and report back.

Edited by nick62 on 08/09/2019 at 16:52

The main problem with the old system was it being gravity fed (from a cold water storage tank). It was prone to "short cycling" and sending water into the header tank via the expansion pipe, (the boiler was mounted no more than 1.5m below the header tank).

There was no particular sludge build-up identified during the flush and the pump was working fine. The old boiler was rated as 80% efficient (35kw) and the new one 90% / 35kw, so the change in boiler efficiency has not made that much difference.

The sealed system set-up is what has had the greatest effect IMHO.

Edited by nick62 on 09/09/2019 at 18:26

Looks like I'm soon going to find this out as well - my boiler has multiple problems (and only hot water for 30sec at a time), likely to cost £500+ in parts alone, never mind labour. A new boiler it is, in my case I think a Vaillant EcoTEC Plus 832, so I can get a good DHW flow.

Unfortunately the location of the existing unit (and where I want the new one to go [many reasons, but a lack of space elsewhere being the main one]) and its configuarion means I'll likely end up spending well over £2k to install the new one. Well at least the plumber is an approved installer so I'll get the 10-year warranty.

I see the current (today) government propose banning gas boilers in new build. Alright I suppose to use electric generated by a gas fired power station?

All nuclear, wind, hydro, solar etc

Well KB, don't discount Viessmann. I had great experience with them. Easy to install, multi flue options and great reliability. Could not say the same for Vaillaint. However you pays your money.................... Cheers Concrete

^^^ Interesting.

Sounds very much as though a Vaillant was the obvious choice.

The more I read about Worcester and Vaillant the more I keep seeing how they are decribed as "Premium" boilers, but, at the same time, I read that a fair percentage say Worcester have more plastic in their boilers than is ideal and they aren't as nice to work on as others ... but that their after care is better than the others.

Personally I've tried to see through the "hype" of those two manufacturers hence looking to see if Intergas was a viable alternative. (I wrote ATAG off a long time ago and I don't think Viessman is a wise choice hereabouts for reasons described). But I may have to admit that the vast majority seem to accept Vaillant as being a sensible option - even if Vaillant do have close ties with Homeserve and Domestic and General (FROWN!)

I have written off the idea of replacing my elderly 'heat only' Ideal Classic in the garage and have moved toward installing something in the airing cupboard (where the, 23 year old, vented HW cylinderand three-way valve currently is).

But there is a major choice between a new, simple, heat only or system boiler plus an unvented cylinder in the aforementioned cupboard - OR fitting a big (35 or even 40 kw) combi in there instead. It's the hot water that concerns me most ....will the shower be affected by opening another tap or flushing a toilet with, even a powerful, combi?

I've provided a new dedicated 22mm cold supply (taken immediately after the incoming 25mm MDPE supply and going straight to the airing cupboard) and have provided a new 28mm gas supply there too - so sufficiency of water and gas isn't a problem - but I don't have enough personal experience of a big, new combis nor of an unvented cylinder - although I looked at two newish Megaflo unvented installations recentlyand both seemed to take a disproportionately long time before hot water arrived at the respective kitchen taps DESPITE neither seeming to have exceptionally long pipe runs to the taps in question.... disconcerting as I thought quick availablity of hot water was one of their benefits?

Don't know how I'll decide.

The problem is that most people don't call a plumber out that often, so, like many trades people, it's difficult to assess their competence or that of alternatives, often becuase we see an increasing number of fake reviews on line - both good and bad.

The original plumber I previously used now only works for a local kitchen fitter and thus won't do ordinary work such as fixing and fitting boilers, presumably unless its part of a kitchen fit-out. Mt current one is fine, and the reason why I'm using him in this case (other than that) is because I'll get the uprated 10 year warranty rather than the standard 5 year warranty (some can uplift this to 7 years).

I understand that other plumbers may be qually qualified, but I suspect mine has spent money to go though a Vaillant training course to be full certified on them to be able to qualify for the longer warranties. I'd rather have that extra piece of mind, and would've done the same for any of the other two premium brands (Worcester and Viessmann) had I gone for one of them. I was that I know my plumber well as competent and he's local that it makes the most difference. Had alternative brands had that, then I might of chosen differently.

I am rather concerned about the potential price though, as the boiler location means I'll need both a 3-4m flue extension (its in a cupboard off the central hallway, no other one possible without drastically reducing usable space), a condensate pump and 7m run to the SVP, all through ceiling voids, both of which will require a reasonable amount of builderwork, as will removing the old boiler, flue and making good the defunct hole in the wall where the twin flue system's air intake went (three replacement bricks, insulation and plasterboard inside). At least connecting to the existing gas, heating, H&CWS pipes and pressure relief discharge should be straight forward.

Given I've asked my plumber to quote for a combi boiler one step higher then normal becuase I want the guaranatee of a good DHW flow rate, it means the boiler alone will cost about £1250 - £1300. The plumber says it could take him and his mate up to a couple of days to fit it all, which could come to £3k, maybe more depending on what builderswork he's including for. Any thoughts? I'm phoning him this evening to discuss further.

I'll let you know how it all goes.

Good points KB. Unfortunately for me, I am very limited in what I can do, for monetary reasons (I'm not working at present, so I can't afford wholesale changes to the existing heating and DHW &CWS systems, even if I wanted to) and spatial ones - my flat isn't that large, but the only two locations a boiler can reasonably go are in the existing hall cupboard, and the kitchen, which is already very small and would further reduce the space available.

I also (to keep within the Regs) have to run the new condensate drain to the only discharge point available - the flat's only SVP. I'm not allowed to run it to discharge externally for many reasons, but the main ones are its outside the demise of my flat and I'm not allowed to carry out work on areas not owned by me or specifically designed to take the drain, which the SVP would be. That work alone will like add £250+ to the bill.

The cheapest location and installation is in the kitchen (as it would also back onto the SVP) and would not require a flue extension, just extending the gas and all the water/heating pipes back to the existing cupboard. As I said, it significantly reduces an already small amount of usable space if it was sited there - the kitchen is only 2.6m x 1.75m to start with.

As regards the boiler capacity, the gas pipe runs under the building (I'm on the ground floor) in the vented space below the damp course, and as such cannot be uprated, thus the 32kW combi is the most powerful the system can accept on the existing 22mm incoming pipe, as it also serves the kitchen hob via a 15mm branch. I checked the new scenario and on worst case usage, the boiler only had 0.1mbar to play with.

A higher output combi (e.g. the bigger 35kW and 40kW+ combis, which I've specced myself for bigger new homes as you said) would likely require, as you say, the main pipe to be changed to 28mm, something that likely isn't possible (concrete floors) and way too expensive/time consuming/disruptive if it was possible. The existing boiler location also is nearer the meter and thus the pressure drop would be lower than in the kitchen due to the shorter pipework run.

The cold water supply pipe comes in under the kitchen and doubles back on a branch to the boiler. Pressure is fine, but I think they original designers undersized the DHW flow from the boiler a bit - all the pipes are run in either minibore (HTG) or standard 15mm plastic, so pressure drops are more than usual. With a 32kW boiler, it should deliver about 12-13 l/min of water at around 45-50degC, good enough for a shower plus a little left over.

I would've liked a lot more so I could run the (hot fill) washing machine at the same time, but again the issues over the gas pipe/pressure preclude that. I didn't want to take the chance with the smallest 24-25kW combis that just about produce the 9 l/min of water at 45degC needed for a shower, especially given the small pipes I have (which I can't afford to change out).

Like many newer-build 'McHomes' over the last 25 years, many were never really designed with replacements and upgraded systems in mind. The problem for me is that a like-for-like replacement of decent quality just wasn't possible, as very few, if any combi boilers are available that are of the non-condensing type.

A lot of these problems are due to poor design from both the original 'engineers' (more likely some less experienced one working directly for the builder) and the architect who designed the buildings overall. It (amongst many other issues) has been one of my bugbears over the years - all too often, too many compromises of significance were forced on design teams to save costs, and one of the reasons I got out of the business 2 years ago.

As regards what to do with the condensate, it's normally far easier for houses than flats. In my case, we can only run it to the SVP, as we're not allowed to run any new pipes outside of the flat's demise and connect into a rainwater pipe or other drain (e.g. an external gully), as any fault in the pipe/installation could cause a knock-on effect, e.g. water (especially condensate itself) leaking onto the ground and destroying plants/grass in communal gardens and/or leaving a slippery residue (especially if it freezes in winter) which could easily be a hazard and result in the owner getting sued.

The same goes for any damage caused by a run of pipe freezing up (e.g. if it's not insulated, too long or without sufficient fall) and the pipe breaks due to the water freezing up. It's one of the major downsides to living in a flat. We can't do things outside the demise of our property because we don't own the land/buildings and if we ran new serives, would be financially responsible for any consequences thereon in, including if the buildings or gardens were damaged and had to be repaired.

The residents association does not have the funds to continually go after such residents in protracted legal battles, so muggins here is putting together a 'do's and don'ts' in this regard for anyone wishing to change their boiler/heating system that might impact others. Again, it's an absolute pain and many times I wished I live in a deteched house - more expensive to buy, but at least all the problems are ones I would be solely responsible for and allowed to fix (within the law, regs etc) as I saw fit. Not in a flat though.

I can fully understand your problems as well - if I weren't financially hamstrung and knew I'd be staying in my flat for a good number of years (or decades) to come, I might've considered a more comprehensive system change, but could've cost me £4k or even £5k, but would have so many options - at a price.

A 'Resident Director' colleague of mine on the Residents Association had so many problems with their old system (same boiler as mine) and the high cost of installing a replacement (similar issues, different flat type) that they junked the lot and now have fully electric heating and hot water - not too expensive to install, but it costs them a small fortune (far more than gas heating/DHW) in higher electricity bills.

Now I'm limited to two, one probably £500 cheaper than the other, but which is just not suitable. It is rather like buying a new car, sometimes you don't choose because there's so many to choose from (at a cost), other times you're forced into a choice you don't really want.

The reason there is such a thing as 'approved installer' status is to promote the brand. An extended warranty is fine, but my guess is the extension after your legal one will have strings attached. I am fortunate that in an earlier life I served an apprenticeship in heating and ventilation. We were 'approved' by several manufacturers as installers Crane, Potterton etc etc. This did mean going to their factories and training, but mainly on repairs and replacing items with new parts. That is where the training is useful. Installing is the simple part. I never felt the need to employ anyone to install my appliances as I had accreditation through work. So I saved money all round. If anything did need replacing there are lots of companies selling spares for every type of appliance, so fitting them was fairly easy for me. I agree if you're entirely in the hands of tradesmen, especially ones you don't know or are not recommended, then it is different, and at least the 'approved' status does provide some peace of mind through a recognised reliable brand name. That is what you are paying for. However, as previously stated, and I make no apology for repeating it, the installer is the key to a good job, well installed, set up and running well. In Andy's case this is even more so with the amount of other work to facilitate the flue etc. then of course to finish off and patch up brickwork, plaster walls etc. All finish trades need to good because that is the part you see. Choose your installer carefully Andy. maybe ask your plumber friend who now only does kitchens, who he thinks is a really good tradesman. It takes one to know one. Don't be afraid to ask for inspection of other installations. Any good installer, proud if his work will be pleased to show you how good he is. Good luck.

Cheers Concrete

Yet another case of the list showing a recent post (on the 2nd December) - but when you come here .... it's not here.

Starting to look as thought it's not worth going to the trouble of contributing if your post is simply going to disappear.

If the tech bloke can't fix it then say so. At least we'd know where we stand.

nice resurrection. still have my ideal. now 22 years old. replaced fan a couple of times. give it a hover out every couple of years. . it's never had a service. hard water area. it's just a matter of time., till the day comes when i have to get the cash out

Older boilers are likely to be less efficient the modern condensing ones - possibly 90% vs 60-70% for something installed in the 1990s.

Also, a boiler of that vintage may have a permanent pilot burning gas non-productively.

& equally importantly that boiler may be running with controls of the same vintage. A modern room 'stat (especially if you don't have a room 'stat at all!) is a relatively cheap upgrade that should pay for itself. You don't have to go all the way to a "smart" one but the price of those is falling all the time too.

<< A modern room 'stat (especially if you don't have a room 'stat at all!) is a relatively cheap upgrade that should pay for itself. You don't have to go all the way to a "smart" one but the price of those is falling all the time too >>

We moved to this house in 2006, to find a fairly recent (1999) combi boiler controlled by an old-style (bimetallic strip) room-stat (probably much older), which had a 'dead band' of about 2°C, so the on-off cycle was rather slow. I replaced it with an 'electronic' stat with digital display showing 0.5° increments - the system now cycles every few minutes, keeping a steady temperature. No idea whether it affects the overall economy. The stat requires a battery, but those seem to last for years.

Short cycling (often a big problem on combis in modern homes, especially flats like mine) can have a big impact over the longer term because the system and components are switching on and off a lot more than one that could cope with those requirements.

Think of it as the difference between a small car with a higher-stressed turbocharged engine and a larger naturally aspirated one. Whilst modern technology should make the former more reliable than in the past, a direct comparison would likely show the latter would be more reliable in the longer term and cheaper to maintain (simpler), with the downside being on-demand efficiency. Similarly between a car with a big V8 engine and a 4cyl one - the former can easily pick up speed without needing to overly stress the engine.

For commercial boilers and larger domestic heating systems, I'd recommend the use of boiler systems with a large water content (but where that is highly insulated). This is why - when it worked - my old Powermax boiler was a good concept.

It had only a 14kW burner, but could easily cope with heating my flat (obviously) without short cycling, but more importantly hot water demand for extended periods (e.g. the shower or hot fill washing machine) because it was equipped with an integral 80L buffer tank of energy to supplement the system. Sadly the concept wasn't so well implemented reliability-wise and from a maintenance-friendly pov.

My current Vaillant compact (wall-mounted) combi short cycles a lot, because the heating requirement is a max of 2.5kW but the boiler's minimum output is around double that, even worse when heating is still required in early spring / late autumn when the load is half that.

Commercial boilers from decent makes like Hoval does this well (they aren't cheap but reliable and long lasting), or you can use smaller sized / output boilers and have separate buffer tanks to achieve a similar result, which can be beneficial as the tanks should easily outlast the boiler if high quality.

Unfortunately, as I indicated in my other recent comments, such systems are very rare in one box on the domestic side or IMHO aren't the most reliable (e.g. the Vaillant high output one with the two small buffer tanks behind the combi boiler, and are just as susceptible to scaling-related issues as the HX, etc on 'ordinary' compact combis)

Older boilers are likely to be less efficient the modern condensing ones - possibly 90% vs 60-70% for something installed in the 1990s.

Assuming a gas bull of (say) £1500 pa and a just a 15% improvement in efficiency is £225pa.

This would take ~10-15 years to pay for itself, but:

• at some point an old boiler will fail - possibly when it is working hardest and the weather coldest.
• spares may not be readily available
• a new boiler will have a service life of 15-20+ years + spares availability
• should still be running long after we have moved on - it is something you replace once
• changing before the old one fails - replacement can be properly researched rather than a panic purchase

Reasons for not changing - you plan to move in the next few years and may as well leave the problem for the next owner. financial pressures make replacement now stressful.

What can make a big difference is the type and age of home you live in, as well as the type of boiler fitted or, just as important, can (physically) be fitted to replace one that is 'old', unreliable' or 'inefficient'.

Somebody living in a relatively modern flat or very well insulated house that isn't large may only have the space for a slimline boiler, and often a combi, because there isn't the space for a hot water cylinder.

As such, the potential savings in installing a new boiler will be far less than for a thermally inefficient (and especially larger) home from the 1980s and earlier, compounded if the home also uses gas for cooking, because the gas saving for heating forms only part of the total cost, more so for small, modern flats (like mine0.

Often, the savings from a higher efficiency boiler (even if it is more reliable as well) won't be recouped until the end of its own useful life. I agree though that with some (less common / unusual design that gets dropped [like my old 1st gen Powermax]) boilers, parts and expertise will become very difficult to find and thus prohibitively expensive.

With some relatively 'old', floor-mounted, non-condensing, heat-only boilers, such my parents' floor-mounted Ideal Mexico, parts and expertise are still common (and thus reasonably priced) because the boilers are quite basic and easy to work on.

Consequently it is viable for them to be viable for 25, 30 years and more - my parents' boiler was installed in 1996 (their home is a 3 bed semi from the 1960s and has a gas hob) and has never suffered from any significant issues, barely more than minor items and an annual service. In that circumstance, I'd recommend they keep it going until parts and labour gets scarce / expensive, and there's a slot-in alternative.

Unfortunately with slimline boilers, especially combis (not so much so for system and especially heat-only), their reliability is akin to that of laptop computers - significant engineering compromises have to take place in order to fit all the bits into a small casing but to achieve a relatively high output, especially for hot water production.

This is why many suffer from breakages with heat exchangers, gas valves, leaks and with the electronics generally. As an analogy, my desktop PC has only suffered from two significant issues over its 12.5 year life (and is otherwise working well for its age), not costing that much to fix (one was under a lifetime warranty), whereas my parents are on their third laptop PC since getting one only 8-9 years ago.

My old Powermax was a very large floor mounted 'combi' (unique concept until recently), but my flat doesn't have the space for a boiler+cyclinder, so when it became uneconomic to keep it in a good state of repair (nearly 17yo), I was forced to get a combi.

The only boiler that is close to my old one is a Viessman, but which costs (if I recall) £3k - £4k by itself, which means I'd have to add another £1.5k - £2k for fitting, due to the boiler cupboard being in the middle of the flat and not on an outside wall.

Often whether to replace or repair and keep it going is a calculated guess, because it's not always easy to know what will happen in 5 and especially 10 years+ in terms of reliability, expertise, legislation and (often as a consequence of some/all of them) issues surrounding spares.

With Viessmans, my area has almost no plumbers who 'specialise' in them, and I'd have to source them from 25 miles+ away, which would add a considerable amount to the cost of the plumber. One thing I have noticed is that independent plumbers (at least in my area) are starting to be more trained up on Worcester-Bosch boilers than anything else. It may be different elsewhere though.

I agree that if you're moving, best to get the lowest cost option that fixes a problem and let the new owner deal with any future issues, as it's unlikely that a new boiler will be much of a selling point or be cost neutral, especially if the heating / domestic hot water system has some design / operational issues that might require extensive work and thus money spent to rectify. The problem comes if a (savvy) potential buyer directly asks a question about such matters, whereby the seller is obliged to be truthful.

Ta for the above replies.

Today a local (7 or 8 miles away) Viessmann accredited installer spent an hour with me. I was impressed and reassured on all counts. Too soon to receive his quote yet (obviously).

We spoke about pretty much every aspect of the installation - and there was much to cover ..... change of position in garage including changing wall flue to vertical, gas suppliy, controls for a heat only boiler using existing vented cylinder, pros and cons of changing from open vent to sealed using an expansion vessel and filling loop. To be honest he had a sensible answer to all the points raised. We spoke about a future possible change from existing (28 year old) cylinder to an unvented ... not to mention whether Viesmann, as a manufacturer, is advantageous over the likes of Worcester, Vaillant, Ideal etc etc etc.

I was very aware that the 100W heat only boiler is different from most others insofar as it has a stainless steel HEX and also the boiler modulates down to 3.2kw. Rightly or wrongly both those points were important to me. The warranty is 10 years if registered on the installer's portal and that is not dependant on fitting their own magnetic filter.

The boiler doesn't incorporate Opentherm from the factory and so he fits whatever controls are suited to the installation. I'll be honest I'm in the dark regarding modern controls and would be in his hands. Simplicity for us oldies is as important as economy to the nth degree.

Of course, the fact remains the existing 28 year old Ideal Classic 50,000 btu boiler (with electronic ignition, not pilot light) is still working and has had a new fan exactly one year ago ( £44 inc VAT and postage !!!! isn't that amazing? ) . But the debate regarding when to replace is acknowledged ... and reiterated above.

My main doubt concerns pressurizing the system and the possible leaks thereafter. He said it's very rare, and it may well be, but it still scares me.

If I did pressurize the heating circuit and there was no leak then fine. If, at some point in the future, the cylinder did start to leak then I'd almost certainly swap to an unvented cylinder.

The installer recommeded fitting a 19kw boiler to take into account the possibility of a new unvented cylinder in the future. The (14) radiators are rated at a total of 15kw plus 2kw for the existing cylinder so that would suggest a 16 kw boiler may well suffice but his preference for a 18kw may well be prudent. It can be range rated and does have that very low modulation figure.

And so to bed.

I thought the main purpose was to save fuel (gas, which can be used once, then becomes the dreaded CO2) rather than your money - which merely changes hands, depreciating slowly, and more can be printed when supplies run low :-)

Interesting point - but I wonder how much emissions performance vs money dominates the choices people make.

Some certainly put the environment first largely ignoring financial consequences.

Some (possibly like myself) will accept a small financial penalty (5-15%?) for environmental good behaviour.

I suspect most, for purely pragmatic reasons, base their choices largely on financial grounds - eg: putting in a £10k heat pump may take second (or seventh) place to family holidays, newer car, new kitchen, paying the mortgage etc etc.

<< (a big PV array) ... should give them both a decent amount of backup in case of power cuts, plus in 'normal' times, they can sell it back to the grid when the rates are most preferential. Payback is between 10-15 years, depending on the cost (each way) of electricity. >>

I don't know how the sums work out in 2024, but our 9-panel PV was installed 12 years ago, with the promise that it would pay back in about 10 years. Hard to judge accurately, but that seems to have been about right. Since then the FiT tariff has dwindled, along with the cost of installation, but I am still smugly happy that our deal was probably better than today's.

In 2011 the largest domestic installation permitted was 18 panels, but we only wanted to fit 9 on the area of roof we had in mind. We could have gone for the lot but chose not to.

I'm following the comments here regarding the make of boiler peoplehave got fitted and their thoughts on them.

A Viessmann accredited fella called the other day. Got on well with him. We're talking a heat only boiler, a 100-W 19kw. He recommended changing from open vent to sealed, using an 18 litre expansion vessel. I'm fearful that pressurizing the 28 year old 10mm microbore system might spring a leak and that would be hard work given the 8x4 chipboard flooring and dot and dab platerboard walls.

It seems Viessmann used rubber hoses (flow and return) to connect the heat exchanger and the insides used to collect crud and block and go crispy with bits falling off and blocking stuff.

I believe they've gone to copper now but will check to be 100% sure. what a bad decision on their behalf ... rubber hoses connecting the HEX!

But there aren't many heat only boilers with stainless steel HEXs to choose from. Viessmann and Alpha to the best of my knowledge.

The system is 28 yrs old. Put in when the house was built.

10mm microbore copper, manifold sited centrally on first floor with 10mm feeds to ground and first floor. 28 year old Ideal Classic 50,000btu boiler with cast iron HEX and 28 yr old indirect vented cylinder, header tank and C/W storage in loft. House walls insulated and double glazed. 14 rads plus cylinder totals 50,000btu (calculated myself with a 1980s imperial measurement Mears calculator.)

System heavily dosed with Calmag cleanser / descaler / inhibitor (£11 per litre from Toolstation) ... been using it for years) seems really good stuff, the water is clear as a bell now. All rads removed and flushed about 12 yrs ago and not been drained since.

Spirotrap MB3 brass magnetic filter been there for ten yrs. I moved in when the house was ten yrs old - for the first ten years I heavily suspect the owner totally ignored it ... it was badly sludged up and can't have had any attention and the boiler had started to kettle. When I moved in it started to get some TLC. After chemically cleaning it and subsequently generously dosing with Calchem 'three in one' it has got cleaner and cleaner and no more kettling. The boiler runs as asweet as a nut .... you may well why am I changing it????? It's had a gas valve, two fans, air pressure switch and I can't remember if it's had a PCB.

The prospective installer isn't going to powerflush it, he'll put a chemical cleaner in, wait a week, return, flush and refill and put inhibitor in. He said the system, when sealed, will be charged to 0.8 bar and will then be subject to whatever increase in pressure is brought about by heating the water. He has quoted for an 18 litre EV and 40mm plastic condensate run in the unheated garage ... both of which I was encouraged by. The proposed boiler is a Viessmann 19kw 100-W heat only. 10 yr warranty if registered by the accredited installer (which it will be) plus 6 yrs warranty on his work.

The only other boiler that I know of with a S/Steel HEX is an Alpha.

No great shortage of combis and system boiler with S/Steel HEXs, it's the heat onlys that are all Ali. (except the two mentioned).

Edited by KB. on 25/02/2024 at 00:37

^^^^^^^^^^^^ All received, ta.

A couple of points raised there.

I honestly don't know what the future holds and how long we'll be here but certainly haven't got plans to move but none of us knows what's round the corner and the older we get the less certainties there are. I'm 73 and the Mrs a couple yrs younger.

However, the fact of the matter is ... the first floor is constructed with 8x4 sheets of (nailed down) chipboard with the skirting fitted after the flooring hence sitiing on top of the boards.

The feeds to the ground floor rads all drop down behind dot and dab plasterboard..

There are 14 rads in total

If anyone thinks I'm going to remove all (or most) of the chipboard flooring and skirting on the first floor (including taking out the hot water cylinder which is also sitting on chipboard) plus stripping plasterboard from the ground floor walls ... then they are mistaken.

I'm genuinely only considering swapping from open vent to sealed system due to the general concensus that sealed has advantages regarding cleanliness, absence of oxygen ease of filling - and the fact that there are a lot more pressurized boilers available than there are open vent. If anyone wanted a combi here then the open vent would have to go. BUT I'm afraid of pressurizing it in case of leaks under the chipboard or behind the walls but I should, perhaps , just take a chance. The biggest liability is probably the manifold in the first floor landing and I think, apart from the manifold, most, if not all, of the 10mm pipe is continuous under the floor so, hopefully less chance of a leak on that.

The boiler is 28 yrs old so I'm thinking it might be best to bite the bullet and update it now while I can plan for the job at my convenience. The fact that a new one might use less gas would be nice but not all consuming.

I do have funds to re-pipe it all and fit new rads but, as things stand, the system works and I don't think is sludged up due to the precautions I've taken and will not give myself an inordinate amount of work and mess to achieve something I may not ever benefit from.

Opentherm is not apparently built in to the heat only 100-W Viessmans. I don't claim to understand it in depth, nor the relationship between it and the boiler controls that do or don't come with the boiler or the many third party controls ... and I suspect many installers don't understand it in depth either. It's a little bit of a nightmare and I don't like delving into stuff that I'm not familiar with but that's how it is at the moment. I have a fair knowledge of plumbing and electrics and other domestic property related things having worked for many years with tools in my hand but Hive, Tado, Nest, Honeywell T6 and Smart Controls controls in general plus Weather Compensation, Domestic Hot Water Prioriy calculations four pipe systems etc etc are above me. And, believe me, if you look deep enough you need a degree in something or other to understand what's published online. Tthose much, much smarter than I might, but I don't.

Edited by KB. on 26/02/2024 at 22:02

^^^^^^^^ Ta.

The rads are all convector, mostly double panel with with one convector with a few small single convectors with one convector (K1 and P+). None are ever particularly hot - they're generally turned down via their respective TRV. It's a warm house. We're in all day.

I would obviously prefer that the boiler was in condensing mode as much as possible but, as you'll have gathered, I'm not going to replace pipework unless forced to and won't change the rads either. None are blocked and I have renewed a couple purely on cosmetic grounds. The TRVs are Drayton TRV4 and the lockshields are all in good nick ... I'll change the boiler and controls and might well pressurise the system and get rid of the F&E (and hope and pray it doesn't leak under the floor or behind walls) but that's as far as I'm prepared to go.

My concerns are ... finding a heat only boiler that I'm happy with (and there isn't much of a choice if you want a stainless steel HEX) plus choosing controls that make the most of the boiler's performance, trying to be reassured the pipework won't leak when pressurised (remember it's 10mm microbore with a manifold on the first floor - and I believe the 10mm feeds are compression as they join the 22mm manifold, and (slightly less crucially) choosing which magnetic filter to replace the one that's there (I fitted a Spirotech MB3 ten yrs ago but in truth I'm not convinced it's actually collecting as much magnetite as a Magnaclean might do .... I like the look of the Fernox Omega and the Sentinel Vortex 500 but suspect the Magnaclean Pro2 might work better than the others (just a pity they have had so many leaks in the past).

Edited by KB. on 27/02/2024 at 16:06

15,000 kWh of gas would have cost just over GBP 1,100 so not much more than your oil.

Viessmann do a good line in combis with an integrated storage tank (as do Worcester) if that might be of interest.

I'm very pleased to hear that. It is/was one of the concerns I had even though there's little scope for two outlets being opened together ... the only possibilities would be one in the shower and the other uses the toilet of opens a downstairs tap. However I'm hoping the issue wouldn't be great as I have provided the prospective boiler with its own 22mm supply taken immediately as the cold water enters the house - it supplys 4 bar pressure and 38 litres per minute flow.

I was considering fitting a pressure reduction valve on this feed to the boiler so that I could ensure it has the same pressure as the rest of the house in order that the shower (s) can have balanced hot and cold feeds (there's a Caleffi pressure reduction valve on the feed to the rest of the house which is set at 3.5 bar - obviously I'd set the boiler feed to 3.5 bar as well. Given that I have 38 litres per min flow I'm thinking I have enough to supply a 30kw boiler, if not a 35kw. Hopefully either may ensure a good and stable shower which shouldn't be too affected by a tap or toilet operating during the shower.

All rcvd. Ta.

Way more, you will probably only get ~11-13 lpm at 40C rise for a 30-35kW combi.

Not sure what you're saying when you say "way more" then say only 11 - 13 lpm - please expand a bit.

I have thermostatic shower valves ..... Mira Excel, albeit the ones they produce in the 1990's but still sell replacement cartridges. Excellent bits of kit. They have settings to swap betwenn high and low pressure. High is considered more than half a bar.

My intention is to replace the present heat only boiler and accompanying tanks x2 and cylinder x1 and fit a 30kw combi (probably either Viesmann 100-W 30kw or Ideal Vogue 32kw)

I have in excess of 4 bar incoming via 25mm MDPE and a new 28mm gas supply going back to the meter.

The boiler has been provided wi8th its own 22mm supply going directly back tothe cold water incoming main supply in 25mm MDPE under the sink.

What controls have you gone with?

What made you decide on the Ideal over the Viessmann?

After a somewhat disproportionate length of time spent deliberating. (probably close to 7 years) I have given instructions to a local installer to remove the HW cylinder, two plastic tanks in the loft and associated 28 year old pipework - and instal a 32kw Ideal Vogue combi. It'll stay in the (attached) garage but be moved closer to the point where it connects to the bathroom thus reducing wasted water. The move also shortens trhe flow and return runs too.

Theres plenty flow, pressure and gas and we just hope there won't be any leaks from the existing 10mm pipework.

I hope it all goes well. I'm due to have some work done on my combi's system - due to *some* contaminant left in the pipes and/or radiators when the new combi was installed, the boiler sometimes makes a banging noise (once in a while if the particles are in the vicinity of the boiler) as the burner starts up. My guess is it is 'kettling' due to limescale (very hard water locally) in the water.

As such, my plumber will be first adding a cleaning / dissolving agent into the system for a day's use under load, then flushing the whole system (including possibly taking all 7 radiators off and doing them individually), then refilling/dosing with the normal chemical additive.

This isn't so bad on a modern system like mine with plastic pipes, not so easy when it's a 40+yo one with corroding copper pipes. I should've got this done at the install - lesson learned.

Not sure whether your system would cope with that, given it's likely to be of that older type and in not so good condition.

Note also that as your new system uses a combi, not a system / heat only boiler, you won't have any heating output whilst hot water is being used. Most of the time, it's not a problem, but occasionally on very cold days during periods of high hot water demand, you may need to adapt a bit, e.g. perhaps overheating certain rooms a bit prior to the heavy HW usage (e.g. two lots of s shower usage / bath fill).

I had an Ideal Vogue combi installed a couple of years ago (albeit the 40KW version).

Ideal insist on a power flush for their warranty.

Mine came with an ESI programmer, which I find not very good. It has some useful functions, but the tightest sensitivity is 0.5 degree. That means if it's set to 20C, the temp has to fall below 19.5 before the boiler triggers and rise above 20.5 before it goes off.

Mine was installed a couple of years ago. I may well be mistaken, or perhaps things have changed.

Totally agree about 'keep it simple'. Mine's got a 'pre heat' option, that keps the water in the boiler at an optimum temperature, to ensure hot water reaches the taps quicker. That was turned off right away!

Ah ... understood.

I guess the feature would be responsible for increased gas consumption.

Can I ask why you went for the 40k rather than a smaller one? I guess your usage dictated the need for a better hot water supply and not a higher heating requirement.

Is delivery time to your taps what you consider acceptable to you? Obviously the nearer the boiler the better, but are distant outlets still iivable with? And does winter cold water temperature have a noticable effect on delivery times or flow rates?

The above points have caused me to query if a combi was/is suitable and after much deliberation I went for one .... and hope I did the right thing.

I'm slightly less troubled by the opening of a second outlet during a shower but will have baited breath in the days following installation.

I appreciate your questions are directed at another member. However, I would like to comment as I had a low output combi (Worcester Bosch 27CDi) installed 15 years ago. I've also had a conventional boiler and hot water cylinder installed in a previous house.

I also have the pre-heat function turned off. To me, one of the main reasons in going for a combi, is that you only heat domestic hot water when you need it.

The boiler with the higher flow rate would be advantageous when filling a bath. However, with just an ordinary shower and a sink, your chosen boiler will cope just fine.

The time taken for hot water to reach the taps is a bit longer than it would take to come from a conventional hot water cylinder. I would say that you can get hot water to your kitchen sink faster, If initially you only open the tap enough to fire up your boiler for about 30 seconds, then open the tap to your desired flow rate. It's only the kitchen sink which I do this with, as the wash hand basin taps and shower have slower flow rates.

A Combi will be fine for your situation. You've done your homework, and you understand how it works.

Personally (having had both) I would choose a combi over a conventional boiler.

Heidifirst said .....

What controls have you gone with?

What made you decide on the Ideal over the Viessmann?

Apologies, I missed that.

On the recommendation of the installer he'll fit Ideal's own Halo control. In truth I haven't looked closely but I guess it'll be a programmer for the heating and a thermostat. I believe it's wireless. At present there's the original Siemens programmer near the cylinder to control heating and hot water times plus I replaced the old basic rotary wall stat with a Honeywell digital programmable stat which has a timer for the heating circuit (a hardwired Honeywell CM 901)

I thought long and hard about the make of boiler trying to work out which might be reliable, which has a stainless HEX, which has readily available parts, which might be familiar to the majority of local Registered Gas Installers plus a dozen other considerations. I was a bit worried about the fewer number of RGI's familiar with Viessman in the event that the chosen one ceased to be available in the future plus I wasn't convinced about Viessmann spares (I could be wrong on both counts though). I also feared the Viessmann might just be a little bit too clever for it's own good ... but I appreciate there's not much logic in that particulare line of reasoning.

Ultimately I felt safer with the Ideal name and the installer has a good reputation local and employs half a dozen blokes so hopefully one might be available if required - as opposed to relying on a sole trader who might not.

That's both helpful and encouraging ... ta.

One thing though - why would the wash hand basin and shower have slower flow rates? I would guess the shower might be restricted by virtue of the thermostatic aspect of the mixer but unsure re. the wash hand basin.

The biggest worry was the pressurizing of the rad circuit after fitting the combi. The present system is the older cylinder and two plastic tanks which, of course, only impart a small head of pressure upon the rads and pipework ... but almost everyone assures me I'm worrying unnecessarily.

Yes, I confess to having done more homework than was necessary. But a leopard can't change his spots etc etc.

My wash hand basin mixer tap is this one.

www.grohe.co.uk/en_gb/eurosmart-basin-mixer-1-2-s-...l

It's listed as having GROHE Water Saving - Less water, perfect flow & maximum flow rate (at 3 bar): 5 l/min. Also, the flexible pipes which feed it (these are part of the tap) have a smaller inside diameter (significantly smaller than the 15mm copper pipework) which help to limit the flow rate.

Basic showers have a flow rate of 3.4 l/min. I suppose the flow is limited by: the thermostatic valve, the internal diameter of the flexible hose and the type/ size of shower head. Mine is about 5.5 l/min, probably as I have a larger shower head. The other thing to remember with your shower flow rate is that it's a mix of hot and cold water, so your boiler isn't providing all the flow anyway.

www.screwfix.com/p/mira-apt-rear-fed-exposed-chrom...t

I get about 11 l/min from my kitchen tap.

As a very rough guide, you can hold a 1 litre kitchen measuring jug under a running tap and count the number of times you empty it in a minute.

You'll only really know if your system can withstand the higher pressure once it's installed. But it's a very common upgrade, and it's extremely rare to hear of any problems.

A lot of the bad experiences people have are caused by not doing their homework and asking the right questions?

Can I ask why you went for the 40k rather than a smaller one?

At the time supply was very limited and it was the last one available. I've ten radiators, two bathrooms, kitchen and utility. It's more than adequate. One bathroom is almost as far as you can get from the boiler (bungalow) and you have to be patient and wait for the hot. I was disappointed at first, but would had to have a pump to deliver sufficient pressure to the showers with the old unpressurised sysytem.

The deliberations are done. Last Thursday and Friday a local, well regarded, firm has removed my HW cylinder, F&E and cold water storage tanks from the loft

Work done by wo installers plus a young lad with me acting as a skivvy and doer of lots of little jobs (which left me exhausted but which I volunteered to do).

They did a cracking job fitting a 32kw Ideal Vogue Max combi with an Ideal magnetic filter plus a shock arrestor and auto air vent and they fitted my own pressure relief valve on the dedicated 22mm cold water to the boiler (taken immediately after the MDPE cold water incoming supply to the house under the sink). They fitted my own small radiator in the airing cupboard too.

The two showers are now mains fed and the heating works considerably better than it did and filling the system is now much easier being devoid of air locks. The heating is noe controlled by a battery powered wireless Halo programmable thermostat.

I'm very impressed with the system and over the moon with thew work done by he installers.I don't think the operation of a remote tap or WC will have a substantial effect on the performance of the shower (a remarkably powerful shower now!). I've fitted a restrictor in he shower hose to reduce the flow/pressure as it was too powerful.

The uncertainty is over and the bonus is the pressurisation of the radiators didn't create any leaks, as I feared it might. 12 year warranty subject to annual servicing, of course and the backing of a local company who answer the phone and seem supremely attentive. I think I got lucky.

I checked and it seems that turning on a tap or flushing the loo whilst the shower is running gives rise to a temporary slight change of shower temperature but the thermostatic design of the (Mira) mixer adjusts the temperature slightly but takes a couple of seconds to do so.... it's noticable but not hazardous or troyblesome. If you turn on the HOT sink tap in the bathroom, next to the shower, it does have a definite negative effect.

"If you turn on the HOT sink tap in the bathroom, next to the shower, it does have a definite negative effect."

Clearly something you should appraise anyone sharing your ablution time with.

:)

Indeed - the problem with combis over heat only/system boilers always has been the large disparity between the minimum heat load and normal hot water loads. Very few combis have a great turndown on heating to avoid short cycling on heating.

It's a far worse issue in more small, modern homes and especially flats, where the maximum heating load is very low.

The only choices are normally to:

1. put up with the problems / work around them (which can be inconvenient for users, especially for homes using gravity-fed CW systems);

2. oversize the boiler on HW load, which makes the short cycling problem worse and can only be done where the incoming mains water pressure and pipe sizes are sufficient to give higher HW flow rates with multiple outlets running.

3. ripping out pipes and upsizing them, which is often either nigh on physically impossible or ultra expensive and very disruptive for long periods, due to their location.

One thing to remember is that there are two aspects to this issue whether the boiler can provide sufficient hot water and at the desired temperature.

As you live in a house rather than a flat, you should have les problems with the boiler short cycling on heating at low demand.

I agree that rarely is it feasible to rip out water pipes to upsize them to reduce flow rate issues for showers. The main issue to be careful about is the limitation of each size of combi boiler to provide hot water for more than one shower.

As you say, as long as everyone at the home is made aware of that, you can make some accommodations to ensure the person taking the shower doesn't get a nasty shock from either a sudden drop in flow rate, or worse still, only (but large) changes in water temperature as other people run a tap elsewhere.

One of the problems with 'older' properties (my parents' home being a good example) where they were designed on a gravity-fed cold and hot water system (other than for cold water to the kitchen cold tap) is that showers can easily get starved of water flow. Showers also are often placed as the last outlet in the system, and are also often the 'index run' (highest pressure drop).

Without ripping out the hot and cold water pipes to go over to all mains-fed (heating pipes were probably ok as they were all 15mm and 22mm), their system would not be able to accommodate a combi boiler.

Their house was built in the early 1960s - I'm not sure when homes started to change over from gravity fed cold water to mains only, but unless the pipes are easily accessible or the home owner doesn't mind the disruption/expense, I'd advise those with such systems to stay with system/heat only boiler + cylinder.

Whether a modern boiler condenses really is only dependent upon the heating system's return temperature (above/below 58degC ish), which is in turn dependent upon the amount of heating required, what flow temperature the radiators have been sized for and depending upon the outside temperature.

This means it'll condense far more in spring and autumn than in winter, giving a boost in efficiency by between 5-10%. Even when they don't, they are about 85% efficient, normally 10-15% better than the boiler they replaced.

Thanks for posting back about your positive experience KB.

As I posted in May, I was sure your chosen size of boiler would be fine for your use.

Going back to the early 1990's there were many Combi's, installed which didn't have an adequate domestic hot water flow rate, leading to the classic complaint that "it takes half an hour to fill a bath".

Unfortunately, this reputation has stuck, even though installers learned and are now recommending boilers with a higher flow rate.

A Combi isn't the right boiler for every situation, but for my needs it's perfect. I've had mine for 15 years.

I'm quite sure your boiler will be just fine in winter too.