boiler size and efficiency

[joshea]

Which is it more cost effective
1. to put in a smaller output boiler and have it running for longer
2. to put in a bigger boiler

Small boiler C26 firebird
bigger boiler C35 firebird

TA

 

[DGOBS]

what is the requirement for the house?
is it a new house?
if so, what was the design temperature differential?

 

[joshea]

The size is 2400sq.ft
Its a new build bungalow, thats well insulated with underfloor heating

The plumber said that I should get away with a c26
I was advised by my brother who has same size house with rads to go with the bigger size of the c35

I have no idea what a temp differential is

Ta

 

[DGOBS]

with underfloor you are looking al low return rates, so possibly opt for the smaller boiler, you only want 40deg underfloor (your brother will meed 75deg flow)

Your plumber is on the coalface here, take his advise (assuming his calculations are correct)

With your underfloor would you not consider a renewable source? heat pumps etc (only good when done correctly)