Gas boilers what do I need to consider

size5

Have got planning for an extension and total gutting of existing house total size 150 mtrsq. What do I need to look for in a gas boiler? From reading some of the threads here I need to look at output in watts(I think):rolleyes:. But how do I calculate how many watts I would need?

Appreciate any advise and any other considerations I might need to look at.

Sparkpea

The proper way to work it out is to find out how much BTUs/KW you need per room, how big you're hot tank is etc and allow for it also.

I work mine out using a domestic heating calculator which works out the cavity walls etc but you can do it online through a web calculator I'm sure.

Normally you can work it out depending on how many radiators there are likely to be in total. I would fit a 50/70 BTU boiler for up to 9/10 rads, a 70/90 up to 14 rads and then a 90/120 for up to about 20 rads

Joey the lips

Simple solution...Ask 3 plumbers the size of boiler needed and your on the pigs back but the way i use to quickly budget

Standard 3 bed 50/70 kero

3 bed and extension 70/90 Kero

4 bed big house 90/120 Kero

5 bed 150 diesel

This is an absolute rough...When you do work out all the correct btu;s by room size dont forget to allow 20000 btu for hot water.

Carlow52

size5 wrote: »

Have got planning for an extension and total gutting of existing house total size 150 mtrsq. What do I need to look for in a gas boiler? From reading some of the threads here I need to look at output in watts(I think):rolleyes:. But how do I calculate how many watts I would need?

Appreciate any advise and any other considerations I might need to look at.

I would have at least 3 zones: upstairs/ down stairs/ hot water/
A variant is a 4th zone for bathrooms.

[ The Rolls Royce solution from an ease of use perspective is to have each room on a separate circuit with a wall stat beside the light switch. PM me if interested further]

trv's on all rads are a good idea but u need to cater for what happens the (zone) circulation pump if all the trv's on the rads close.
3 main options: use a bypass valve or get an intelligent pump which can sense what is required
the classic solution was to leave one rad, normally a bathroom with no trv



The reality is that u rarely need all the rads plus the HW all going full blast at the same time: this full blast approach leads to over sizing and waste.

eg: If u time the HW to be done in the morning before the rads then u dont need to include the HW as an extra.

This approach uses a smaller boiler which if modulating/condensing will be very efficient

yoshytoshy

size5 wrote: »

Have got planning for an extension and total gutting of existing house total size 150 mtrsq. What do I need to look for in a gas boiler? From reading some of the threads here I need to look at output in watts(I think):rolleyes:. But how do I calculate how many watts I would need?

Appreciate any advise and any other considerations I might need to look at.

A profesional can size things for you ,as long as you know what insulation will be used in the extension.

It's almost impossible to work out the heat requirements without seeing the walls and windows in the house.

I wouldn't worry about it to be honest ,anyone who you get to price the job should be able to calculate the heat you need. I do calculations while I'm looking at jobs.