Our combi (Ideal) is ok when the heating is on you get instant hot water, but when you want hot water any other time it takes 3 min of pouring off cold water before the hot comes through. This works out ok when pouring a bath but not for doing the dishes
Don't know is certain manufactures are quicker than others
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Most of the delay in getting hot water at the tap will depend on the length of the pipe 'run' from the boiler. I think all combis fire up and generate hot water PDQ but it takes time for that water to get to where it is needed.
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I have a combi in my house and I am a fan. When you turn the hot tap on, it takes a minute or two to produce hot water but no longer. It depends on the demand for water in the house - if you're trying to run volumes of hot water in more than one location (eg shower and hot water intake washing machine) it can be slower because there is no "on demand" pre-heated water. But in return you don't lose the space of the hot water tank, you don't pay to heat water you're not using and in the summer the boiler isn't used unless you need it and not just because the timer says it's time to heat a tank up.
Wouldn't recommend them for families or high occupancy dwellings though.
And if you really don't get on with it, you can almost always replace the system with a traditional boiler at a later date.
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My understanding is that the outlet temperature of the boiler is thermostatically controlled and therefore the rate of hot water flow depends on the temperature rise, which can be considerably higher in winter then in summer beacuse of the lower water inlet temperature. Put another way, the flow times the temperature increase (which will be higher in winter) is proportional to the boiler heating capacity which is fixed. Therefore if the temperature rise is higher the flow has to be lower.
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L\'escargot.
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We have a multipoint water heater which works on the same principal as a combi boiler. You will set the thermostat on the boiler and find the flow of hot water is constant, but during summer due to warmer ambient air you will need to add more cold water. As cold water is under higher pressure the flow will increase, but it's due to more cold water entering the system and not the warm water being heated less. Filling our bath to a decent depth takes about 5 minutes. As others have said having a shower and running other taps or using the washing machine can cause supply problems as flow through the boiler is reduced.
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Our combi (Gloworm) is very much an entry level model - as such, there aren't any thermostatic controls on the hot water. As you turn down the flow, it gets hotter. Once you get used to this, it is easy to set the flow rate to suit how you want to use the water.
For example, to get really hot washing up water, I run the hot tap really slow, and then I do the glass ware as the sink is filling, so I can also rinse the glass under the still running hot tap.
For running the bath, I just set the water running, and have a shave while the bath is filling - but it certainly doesn't take 10 minutes!
Just after it was instaled, we had lots of trouble (the installers didn't install it correctly), and eventually a knowledgable chap from Gloworm fixed it - but he also turned down the main hot water flow valve on the boiler so that even if you open a tap fully, there is enough restriction to get hot water at a reasonable temperature - he set it up with a calibrated cup flowmeter, and it works very well.
Number_Cruncher
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And if you really don't get on with it, you can almost always replace the system with a traditional boiler at a later date.
That's comforting to know. There is in fact a built-in cupboard which could be used to house a hot water cylinder. It makes me think that the first owners were given the choice of a traditional boiler or a combi.
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L\'escargot.
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I think the combi will have the edge when it comes to fuel costs. I installed combi when we moved to our bungalow and now have 7 years of stats to show it was the right decision for us at the time. The delay for hot water at the tap is a function of the length of pipe run. Not a problem for our small bungalow as the combi is centrally located and all pipe runs to kitchen & bathroom are short..
Phil I
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I agree with everything Duchess said except;
>>Wouldn't recommend them for families or high occupancy dwellings though.
I have a a family and a never ending stream of long stay visitors. We have a combi boiler and it is superb. The water flow doesn't reduce if the water is colder, but the boiler burns longer. The water is delivered at 82 degrees. In the summer a wild guess would say that the boiler was burning on and off but for probably 30%-40% of the time that the tap is running. In the winter that can rise to another guess of 50/60%. Never does the delivered water temperature drop below that set.
I suspect that long runs could be a problem, but we solved that by having another boiler at the other end of the house.
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You need to get a good plumber (do they exist???) who knows about combi's. There are many different specs. I couldn't wait to rip out ours and replace it with a conventional boiler since the flow rate of our combi was pathetic. I suspect someone who didn't know Adam from Eve fitted ours. Had we known at the time we may have bought another house. Also as we wanted an Aga having a combi made no sense.
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>>Also as we wanted an Aga having a combi made no sense.
Out of interest, why not ? I have both.
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Because the Aga provides enough hot water itself for our needs and runs four radiators. Also we wanted to be on one fuel type e.g oil. When we have guests we can then fire up the reserve boiler which is oil.
I suppose we could have got a gas Aga although given gas prices today maybe we did the right thing.
I am not sure whether this makes sense to you - it did to us at the time...
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I presume that the Aga must have some kind of backboiler behind it ? I wouldn't have the space to do that since ours is against an external wall.
Other things against using the Aga for heating/water for me were...
The kitchen is not independantly heated, the Aga does enough on its own. If it were I would have to have pipes showing moving around the kitchen (Stone walls - literally stone, large, rough, pieces of it.).
The house is reasonably large, pumping the water up to the top of the house would have been an issue.
Previously the house had three cold water tanks and two boilers & immersion heaters - with combis I was able to get rid of the lot.
An Aga couldn't cope with 35+ radiators so I would have had to have two systems.
I wanted an Aga hotter/colder at times which didn't coincide with when I wanted heating or water hotter/colder.
I actually deliberately went for different fuels. The house has mains gas, bottle gas, oil and electricity. I had some vague idea that it allowed me to manipulate which fuel I used and avoid those which were more expensive that week. Naive, I know - I'm inventive, not smart.
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No, inside it. Don't ask me the technicalities but it's described quite well on the Aga web site. Our Aga produices our hot water too.
JH
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We had a Combi boiler in our student house at Uni, and that used to take an age to run a bath, over 20 minutes, but that was over 10 years ago and the boiler was probably faulty (everything else in the house was!).
In our house now the combi works fine and fills the bath in a perfectly reasonable time.
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Combi boilers are to all intents and purposes a compromise - and not a very good one at that! They are complex, prone to breaking down, and expensive to fix (read fix by replacement) - they are, however, cheap and compact to install, which is why builders and plumbers like them. Typically they are 28 - 30kW - this can make a 35°C temp rise on incoming water (which will get you from 5°C inlet in winter to 40°C) at about 12l/min (ie you will get 12l/min of water at 40°C). Thus to get 100 - 120 litres in the bath it will take 10 or so minutes. If you're using the water (eg shower) there's none available for anything else. Once the boiler has switched to water, the heating goes off whilst you run the water -OK for one shower, but 6 in a row, and the heating is off for an hour effectively. As noted, if the boiler is cold and you demand hot water you have to heat the entire boiler, then the boiler water, then you start heating the water - which is why it might take 2-3 minutes to get hot water at the tap (and if you run the tap flat out to get it faster the opposite happens!). The 'efficiency' of not heating the tank is severly compromised in these situations...
One thing the revamp of the central heating in my house this summer will NOT be featuring is a combi boiler......!
Don't know what Mark's got, but it doesn't sound like a combi - unless it's a very big one (like 80+ kW!).
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RichardW
Is it illogical? It must be Citroen....
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>>the heating goes off whilst you run the water
That is true, and it is a pain. We had exactly that happen in the winter when a bunch of showers were had in a row. However, in a house that's either better insulated than mine or less populated, I wouldn't have thought it an issue. Or didn't have South Americans in it who seem to believe that less than 4 showers a day is a bit grubby.
It most certainly is a combi, although admittedly quite a big one. However, don't ask me about kW or other techie stuff, way beyond me. Would it be written on it somewhere ?
Even stone cold I have never had it take 2-3 minutes to get hot wated. I doubt if its anything approaching even 1 minute. A bath fills pretty quickly - about the time it takes to get two children out of their clothes - and its a big bath, slightly over 6 ft long I guess since I can lie down flat in it.
The pressure coming thorough our combi is almost 3 bar if that makes any sense to you. It means nothing to me. I just know that our mains is at 4bar so we had to have a pressure reducer to take it down too 3.
I think the point that comes out in the end is that there is not really either good or bad. The point is to get what works for the particular situation you are dealing with, the demand you will place upon the system and the availability of cash and space.
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There?s a lot to be said for a slower filling bath. Mine fills quicker than a manic hotel bath, I only have to leave the bathroom and be pre-occupied for a minute or two and it washes over and starts to flood the carpark below us.
Also Combis are fantastic for high occupancy. We used to have strings of Polish lodgers back in the UK all coming home from work and running a bath. When we conjugate at my parents? house at Christmas, two baths in a row is all you get from one hot water tank.
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I have both systems, a conventional boiler in my house and a combi in a cottage.
To my mind it is a no contest - I am very disapointed with the Combi.
Apart from the disadvantages listed above - low hot water out put, heating off etc, there is another disadvantage. Because of the time taken to fill a bath, a shower is used most of the time. The temperature can be set OK but initially it is using the warmer water from the cold water pipes in the house(which are probably at 20C or so) When this is used it starts to draw water from outside and in the winter this can be 5C or so and the boiler simply cannot cope and heat it up.
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You must have an inadequate combi for the demand, I don't have any of the issues you describe.
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You must have an inadequate combi for the demand, I don't have any of the issues you describe.
Mark,
This was stated in a post above
" Typically they are 28 - 30kW - this can make a 35°C temp rise on incoming water (which will get you from 5°C inlet in winter to 40°C) at about 12l/min (ie you will get 12l/min of water at 40°C). Thus to get 100 - 120 litres in the bath it will take 10 or so minutes. "
My Combi is a Worcester rated 30kWh(102,400Btu/h) which is pretty big?(it copes with heating the cottage very easily with the water temperature for the CH being 82C) but the nominal maximum flow rate for hot water is only 9 litres/min(+/- 15%) The problem I outlined above is that initially it is warming water at an ambient 20C for the shower and when that runs out and it gets water at 5C and goes luke warm. It can be readjusted, flow reduced etc but it is a bother -especially when you are wet and soapy)
Incidentally I spoke to the British Gas servicing man and he said they get loads of calls in the winter complaining that their Combi is not heating water sufficiently and he confirmed mine is working well.
So clearly it is inadequate for the demand, but I guess most of them are in that respect.
What is your combi rated at?
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>>What is your combi rated at?
Would you expect it to be written on it somewhere ? If so, I'll go and have a look.
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MArk there will be a plate somewhere with its rating in BTUhrs - it mightbe well hidden. Failing that the model number and a quick web search should tell you.
I have indirect boiler and much prefer it, tho I have such a huge bath it empties the hot water from the storage tank at only half full.
The one really good thing about combis is that they are easier to design and install. Far too many indirect systems are stupidly designed and installed causing problems.
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TourVanMan TM < Ex RF >
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Don't miss the sale of the house you want over something so trivial. Live with it for a while and if it doen't work for you change it for something better. We have a Bosch Worcester Combi, this has a small heavily insulated tank which holds sufficient hot water for half a bath by which time the water coming through is piping hot. PU towers is a large rambling sort of place and if it works here it will work anywhere - trust me. Totally reliable for the last 9 years (apart from a very minor glitch). We had a French made "thing" before which, put i like this, put me off French made electrionics for life - utter rubbish.
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Combi boilers get something of an odd press. People either love them or hate them.
Ours is pretty much what's required for a family of four living in a typical semi. We have a short pipe run downstairs, so we get very quick hot water. Upstairs, it's a longer run, so it's slower. I've never suffered the "cycling" that people seem to refer to above.
Benefits:
1. Come back after three days (or weeks or months) away, turn the tap on and hot water comes out.
2. Only uses gas when you're heating water (or the CH is on). I hate the idea of keeping a tank of water hot for no purpose.
3. We have two mixer showers that run at mains pressure, so no need for pumps, etc.
Negatives
1. Apparently more complex and expensive to repair.
2. If the water is switched off, you don't have an emergency tankful.
3. I can't fit my solar heating panel to warm a tankful of water.
V
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Negatives
4. If it goes wrong you have no hot water, whereas an indirect system normally has a back-up immersion heater element.
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TourVanMan TM < Ex RF >
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By the way, when I say delay in getting hot water, I'm talking about 15 seconds downstairs and 25 upstairs.
Nothing like " it might take 2-3 minutes to get hot water at the tap" as mentioned above.
I've had experience of three combis now and NONE of them has taken 2-3 minutes to get hot water. That must be exaggeration. I don't believe that anyone would ever put up with a 2-3 minute delay. (and as regards a comment about the CH being off for an hour I don't believe many people run 6 baths one after the other - it assumes zero seconds for the length of the bath).
V
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>>Failing that the model number and a quick web search
I think its this one.....
www.discountedheating.co.uk/shop/acatalog/Turbomax...l
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>>Failing that the model number and a quick web search I think its this one..... www.discountedheating.co.uk/shop/acatalog/Turbomax...l
It certainly has a higher output than mine with a DHW flow rate @ 35oC temperature rise of L/min 15.1 . Although according to those figures it will still take 8 minutes to run a 120 lt bath, and if the water temperature is 5C the water will only be delivered at 40C.
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Bath water is delivered at 79-83, it tends to fluctuate as the boiler kicks in and out. Certainly its hot - you need cold water as well, although with a cast bath the initial water cools off pretty rapidly. Filling a bath in the winter, the water is delivered at the required temperature and still the boiler wouldn't be running much mroe that 60%/70% of the water flowing time. I can't believe it takes 8 minutes to fill a bath, but to be fair I've never measured it.
Whatever, however the figures work out that particular boiler powers one bath, four hot taps, and about 25 radiators. And does it most satisfactorily too. Never yet run out of water, had water too slow, or had it too cold. The CH works fine too, although it is split into three zones with about 8 radiators a zone. The rest of the house is heated and supplied hot water from other boilers.
My point is, that it works for me. It might or might not be somebody else's choice, but unless horribly under-powered I can't see it being a disaster.
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