Working Out What Boiler

[Too Late]

Hi.

How do I work out what size boiler to get? We are installing underfloor heating throughout our 5 bedroom house. Is there a tool to calculate what size I should be looking at?

Thanks
N

[dirkgently]

Too Late said:

Hi.

How do I work out what size boiler to get? We are installing underfloor heating throughout our 5 bedroom house. Is there a tool to calculate what size I should be looking at?

Thanks
N

you need to calculate the heat loss from the house then add on for hot water requirements (usually 3kW)

quick and dirty

[caziques]

Single or two storey?

What thickness slab?

Square meterage where pipes have been laid.

In very general terms a boiler that is too big will short cycle leading to loss of efficiency.

I work on 50 watts a square metre for sizing purposes, but this is NZ and I only install air sourced heat pumps.