Which boiler will be suitable for extended house

[Theknight63]

Hi, I'm currently extending my house and need advice on the type of boiler(s). It will be 4 bedroom house with two bathrooms with 4 people living there. As we have use all possible areas there is no where we can put the water tank and therefore looking for boiler(s) which will be suitable for approx 15 radiators and other water requirements...

I would prefer to put something energy effecient but not too expensive.. British Gas made an appointment but didn't turn up and gave me a quote without discussing my requirements.

Can any one help me here please? or point me to website where I can entre the room sizes and get some help here..

Thanking you all in anticipation.

 

[D_Hailsham]

Hi, I'm currently extending my house and need advice on the type of boiler(s). It will be 4 bedroom house with two bathrooms with 4 people living there. As we have use all possible areas there is no where we can put the water tank and therefore looking for boiler(s) which will be suitable for approx 15 radiators and other water requirements

So you have no room for a hot water cylinder? If so you need a combi boiler. The problem with that is that it will have to be a big one if you want to use both bathrooms at the same time. The problem then is whether the cold water coming into the house has a high enough flow rate and sufficient pressure to meet this need.

You then have the second problem of the heating requirement of your house. Combi boilers are frequently OK for hot water but oversize for heating.

Can any one help me here please? or point me to website where I can enter the room sizes and get some help here

Do you want to find out the size radiators for the extension? The builder/architect should be doing that as he has to provide heat loss information when applying for building regs approval.

The total heating requirement can be calculated by using the Sedbuk Boiler Calculator or EST online boiler calculator

I would prefer to put something energy efficient but not too expensive

How unusual.

British Gas made an appointment but didn't turn up and gave me a quote without discussing my requirements.

BG will, invariably be the most expensive. Get the names of three reliable local contractors from friends and neighbours and ask them to recommend a solution and cost. You can also use the government backed TrustMark Scheme to find a local installer.

 

[mickyg]

If your getting a combi, whatever you get will cope with your heating requirements. I'd get an expert round to discuss your requirements and check out your water supply flow and pressure.

 

[ServiceNumpty]

With those requirements, call in an installer, you may be surprised where what will fit. I think you are on the extemes for a combi. Depends where abouts are you, I may be able to give you a number.

Mike

 

[Theknight63]

Many thanks for a prompt response..

I am not sure about the water pressure... (how can I check that?) I am sure once the guy from Yorkshire Water mentioned that the minimum it should be 30m however, he didn't confirm what is the actual pressure at my property though.

Someone also suggested Megafloor system available in combi boiler.. Is this something can you advice me on as I can't find any reference to Mega floor system on the interenet yet...

You have to excuse my knowledge in this area and this why I am getting more and more confuse...

Sincere regards.

 

[Theknight63]

Thanks for your prompt response...

I am in Dewsbury (near Wakefield) will appreciate if you can give me the number who can offer professional advice..

Cheers!

 

[D_Hailsham]

If your getting a combi, whatever you get will cope with your heating requirements.

I agree that it will cope, the question is: how efficiently?

Let's say you install something like a Vaillant Ecotec plus 837 to meet the HW requirements. The central heating output will modulate between 12kW and 28KW. If the requirement is below 12kW the boiler starts cycling, which is less efficient. With modern well insulated houses, and even old houses which have had insulation added, it is quite possible that the heating requirement is below 12kW. This means that the boiler will never modulate, so it will not be as efficient.

Don't forget that the heating requirement is calculated on a worst case, i.e outside temperature of -1°C. The requirement reduces as the temperature rises, so at 10°C it is approximately half. Ideally the max output of a boiler should be sufficient (or slightly more) to meet the lowest temperature requirement and then modulate down as low as possible. Unfortunately most boilers can only provide a 3:1 modulation range at the best.

 

[mickyg]

If the requirement is below 12kW.

suitable for approx 15 radiators

I know what your saying but its pretty unlikely wouldn't you say.
You could then argue that adding trvs makes boilers innefficient.

 

[D_Hailsham]

If the requirement is below 12kW.

suitable for approx 15 radiators

I know what your saying but its pretty unlikely wouldn't you say.
You could then argue that adding trvs makes boilers innefficient.

It's not as unlikely as you would think. There have been several cases on here where large combis have been installed, eg. Vaillant 937, to meet HW requirements but the OP has come on complaining about the poor heating performance. This has invariably been resolved by range rating the heating output, in one case from 28KW to 15kW. But the 937 can only modulate down to 12kW, which is equivalent to an outside temperature of approx 3°C. So provided the external temperature is below 3°C the boiler will modulate; any warmer and it will be cycling on/off. As the number of days that the temperature is below 3°C is relatively few (present weather excepted), the boiler will spend most of its time in on/off mode.

I don't see why you think this means TRVs could make the system inefficient.