My daughter has decided she needs to replace the existing (unreliable and ancient) gas boiler in her big Victorian semi. It's a big house on three (or even four) floors and there are around 20 radiators, two showers (one electric) and two baths plus all the usual other hot water consumers like kitchen, washbasins, etc.
She is considering a combi but knows that a few years ago at least it probably wouldn't be recommended for such a large house, are modern combis more up to the job or would it still make more sense to go for a system with a hot water tank?
Also, what are currently regarded as 'good makes' of boiler?
She's in Ipswich by the way if that's at all relevant.
Personally I would not consider a combi in a big house, having had experience of varying shower, sink, and bath temperature associated with long pipe runs and/or multiple occupants drawing hot or cold water. I've had two unsuccessful combis in this house, but my recent System boiler (Vaillant) is brilliant.
Up to a certain size of house (mine is probably similar to yours, although different in construction being two cottages knocked together), a single hot water tank should be fine. I have two Stuart Turner pumps, a double to feed the main shower, and a single for the rest of the DHW which ensures a fast feed rate to the kitchen and the bath. The hot water tank also has an immersion heater which gives you the same hot water as usual if there is a problem with the boiler or the gas supply.
A colleague of mine who had a *really* large house found he needed an "industrial" boiler to provide sufficient heat, and he had a couple of the small under-sink electric water heaters with storage tanks in remote utility rooms, etc so that he had effectively instant hot water everywhere.
As regularly posted here, both Worcester Bosch and Vaillant are considered by many posters and also by Which magazine to be well-made and reliable products.
I think the first step would be to estimate the potential total heat demand by assessing roof, window, external wall area and U factors using one or more of the available calculators. Someone will probably have an up-to-date suggestion.
Our house is kind of rambling and my biggest regret is not fitting some sort of gas instant water heater for the kitchen and utility room. Long pipe runs from the tank to the kitchen must waste a fair bit of energy.
Of course it depends on where you can put your tank. Worth thinking about a small combi/multipoint water heater (or even electric storage heater) just for the kitchen.
What make is the existing boiler? If it's a cast iron lump and less than 50 years old, find a real gas fitter and get it mended. A combi without a tank is unlikely to be able to cope with the baths and it needs good water pressure to function with showers.
We solved a similar problem - the new kitchen is a long way from the hot cylinder in the airing cupboard - by installing a Quooker water heater under the kitchen sink. This stores 7 litres of boiling water, and feeds both a boiling water tap for making tea and coffee and hot (blended boiling and cold) water to the sink tap. In absolute terms, it's more expensive to heat water with electricity rather than gas - but this is offset to some extent by only heating the water you actually need for hot drinks and by not wasting a long pipe full of hot water every time you run the tap. Not to mention the time saved!
You can make the hot from the tank circulate via well insulated pipes to give quick access to the hot water on a long pipe run. But it is better to site the storage cylinder to avoid a long run. Or even have two - if the bathroom(s) are a long way from the kitchen.
Yes, but there is *some* correlation between the size of the house and both the number of occupants and the amount of hot water (and heating) they might need/use. :-)
Its a Zip Aquapoint and is 10 ltrs. For me recovery time isn't an issue, but for info I think it's 2.2kW so a few minutes if you actually empty it.
There are additional issues when connecting to mains water, like a non-return valve and expansion vessel or a relief valve. So sometimes aren't as simple to install as expected.
You may find the heating load is actually less that you expect. My 24kW system boiler (Vaillant) copes just fine with 21 rads plus hot water. Combis tend to need to be more powerful to cope with the hot water load rather than the heating.
Depending on the house layout it might even be worth doing both. Many people seem to ignore the option of using a combi to heat a hot water cylinder. In some houses with say a kitchen a long way form the cylinder location, it can make sense to have the combi deliver hot wholesome water to the kitchen tap and the tank service the rest of the place.
The other option for "instant" hot water is to lag all the pipe runs and fit a secondary circulation pump. This delivers truly instant hot water to all taps.
Also if they have a cold mains supply with decent flow rate and pressure then consider fitting a heat bank or an unvented cylinder in place of a conventional gravity system. That will give mains pressure hot water everywhere with no pumps, and no need for loft tanks etc.
Worcester Bosch and Vaillant ate the usual recommendations here.
Just remember to give the plumber a high six when you meet him ;-)
The boiler needs to heat the house and as this is large victorian place it'll proably leaking heat like a sieve compared to a similar sized modern place.
A gotcha with installing a modern condensing boiler might be radiator sizing. For a condensing boiler to work in condensing (most effcient) mode the return temperature has to be around 50/55 C with the normal
10 C drop across the radiators this means the flow is only 60/65 C. The old radiators are probably sized for a flow temperature of 70 or even 80 C. At 60 C flow the radiators just can't chuck out the required heat.
The most comprehensive is proably the Myson one but being comprehensive makes it a bit complicated for the novice. There are simpler ones out there but they make assumptions or limit building elements to more recent things. It's a trade off...
1) Steady state loss when the building is up to temperature and it's cold outside;
vs
2) How fast do you want the place heated up from stone cold, or even "cooled down all day 'cos you were at work".
I have some fairly good figures from metering electric heaters which I'm basing my choice of radiator sizes on.
4x2kW oil filled rads will hold my house even in the middle of winter. But go away for a week and see how fast the same 8kW will get it back from say 10C throughout - and the answer is "very very slowly - like a day or two to return to comfortable".
So you want to calculate (1) and probably double it for (2) to have any sort of reasonable response from a stone cold start.
I would always used oversized rads. In your case if you can have some form of weather compensation, manual or otherwise, you might get your boiler going in to condensing mode more than you think.
Shame return temperature limiter valves are so expensive, otherwise
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