Can a 12kw boiler ever heat a 4/5 bedroom house with 3 bathrooms?

[bradymd]

Hi - I'm a homeowner, not a DIY person.
My 20 year old Gloworm boiler needs replacing.
British Gas quote is ok at £6100 for a 24kw replacement -valiant ecofit 625 system boiler. The tank/heat exchanger and copper pipework bring the price up.
OK so I object (rightly or wrongly) for the extra copper pipework ruining the look of the house outside so shop around. The gas safe rules demand it.
So a new company offer to charge £7000 to put a 12kw valiant pure system boiler (no additional pipework). But I don't feel I'm on top of their smooth explanation of how they can manage to do that. (Smart heating, condensing boiler etc). So, more expensive and less work really. This is not my world but Mr Google suggests this doesn't add up. The company seem OK .. website, livery, spiel, vans, google reviews. Not happy they didn't itemize and not happy they went £1000 over what I thought was already a high quote. Is there some magic they are offering? Or are they magicking away my money?

 

[EvilDrPorkChop]

Depends what size of 4/5 bedroom house it is, in addition to how well insulated it is. What is the current size of your existing boiler? Most modern houses 4 bed new build houses will have a 12kw boiler for instance.

In terms of heating load, 12kw can be quite a lot of radiators. You could do it with HW priority thus you relieve some of the load.

I'd stay away from the EcoFit Pure too. Had a few issues with them. You want the EcoTec Plus system instead. Solid boiler.

 

[ShaunCorbs]

Any of them done a Heatloss eg measured all of your rooms and windows ?

 

[bradymd]

Depends what size of 4/5 bedroom house it is, in addition to how well insulated it is. What is the current size of your existing boiler? Most modern houses 4 bed new build houses will have a 12kw boiler for instance.

In terms of heating load, 12kw can be quite a lot of radiators. You could do it with HW priority thus you relieve some of the load.

I'd stay away from the EcoFit Pure too. Had a few issues with them. You want the EcoTec Plus system instead. Solid boiler.

OK I didn't appreciate new builds for large houses would be 12kw. So thats interesting.
The House is a Town House (3 floors, built 2004) end of terrace. Can get cold on the ground floor.
The Glowworm Micron 70FF is 20kw I think.
There is 17 radiators and 3 bathrooms, so most sizing tables say more like 24kw.
I will read up now about EcoTec Plus.

 

[bradymd]

Any of them done a Heatloss eg measured all of your rooms and windows ?

Both british gas and the second plumber measured up to get the overall sq footage of the house. But "heatloss" I don't know about that really. There is some kind of heat loss on the ground floor but the house is not too bad otherwise for insulation - if thats what you mean.

 

[EvilDrPorkChop]

OK I didn't appreciate new builds for large houses would be 12kw. So thats interesting.
The House is a Town House (3 floors, built 2004) end of terrace. Can get cold on the ground floor.
The Glowworm Micron 70FF is 20kw I think.
There is 17 radiators and 3 bathrooms, so most sizing tables say more like 24kw.
I will read up now about EcoTec Plus.

I suppose the question is why aren't they putting the same output back? As I assume the gas pipe is big enough for your current boiler.

As @ShaunCorbs They should do a heat loss calc if the output is in question. The online calculators are just generic.

 

[ShaunCorbs]

The cold spots might be down to either too small of a rad in that room /sludged up one or an overall over-demand on the boiler

Tbh I would do a Heatloss Calc and see where you end up

 

[bradymd]

The cold spots might be down to either too small of a rad in that room /sludged up one or an overall over-demand on the boiler

Tbh I would do a Heatloss Calc and see where you end up

Using an online calculator the 13 rooms totals up to about 12 kw.
It's end of terrace town house and can be cold, doesn't catch the sun, there are 17 radiators.
So why would some sizing tables (and most plumbers including British Gas) says 24kw and other say 12kw? Madness...

 

[Chuck]

So why would some sizing tables (and most plumbers including British Gas) says 24kw and other say 12kw? Madness...

12kW seems low for the house you are describing unless it has had a lot of external insulation applied, which would be unusual and you haven't mentioned.

 

[ShaunCorbs]

Using an online calculator the 13 rooms totals up to about 12 kw.
It's end of terrace town house and can be cold, doesn't catch the sun, there are 17 radiators.
So why would some sizing tables (and most plumbers including British Gas) says 24kw and other say 12kw? Madness...

Some just use rules of thump and oversize which doesn’t help did you work out if your rads are big enough?