House doesn't need 30kw at present, but might do in future...

[JPE234]

We're looking at a new boiler system from regular to combi because we would like to use the space where the hot water cylinder currently sits. We have a large 3 bed semi and have an ancient 18kw Potterton boiler with 7 radiators in the house. Heat loss calculations not yet completed.

We've been told we don't necessarily need 30kw+ at the moment, but for future-proofing reasons (extra bathroom, increased hot pressure at mains etc) 30kw would be fine and not be too large so as to be over-efficient.

Is this sensible?

 

[king of pipes]

A two bathroom property may or may not be suitable for a combi boiler ? as the supply of hot water is only really suitable for one outlet at a time it really depends on your usage and the occupancy, the heating load is often adjustable and can be down rated in the boiler settings , house builders often put in large kw combi boiler in a 4 bed property with a family bathroom and a ensuite be guided by your chosen engineer. Kop

 

[Timmy D]

Anywhere from 25kw-30kw will do one shower.

If you’ve got the mains flow rate 20lpm+ and put in a 37kw+ combi with flow restricted showers, you might get 2 showers at once.

37kw combi - around 14lpm hot
14lpm hot mixed with cold for shower - comes out around 20lpm.
2 flow restricted shower at 10lpm each - 20lpm.

But it’s very close.

A better expectation for a 37kw+ combi is a shower and hot tap running at same time.

You will also likely need a gas pipe upgrade.

 

[JPE234]

You will also likely need a gas pipe upgrade.

Thanks for the response. Currently got a 22mm pipe, will that be enough?

 

[king of pipes]

Depends on the length of run from the gas meter and what kw of boiler you end up with , but be prepared to upgrade with anything higher than 24 kw and a very short distance. Kop