What size boiler

[pampers]

I normally dont look at the size of the boiler presently installed,i size the boiler for the job and usally go a size up than is possible to get away with.

If you had a incorectly sized boiler already fitting another the same size just as it was there already isnt going to help much.

 

[x-man]

You state that your old boiler is 14.7kw. Is that net or gross?

Net output. Why do you ask? Don't all manufacturers quote net output in their sales literature? I have found that you usually have to dig quite deep (in the technical sections) to find the boilers gross input and gas consumption.

Some old boilers quote net and some gross. Whether its net or gross it is simple to find, the front of the boiler or literally in the front of the manual.
Why don't you display your calculations for the new boiler output you desire for viewing as undersizing a boiler can be a costly mistake

 

[DavidJW]

Why don't you display your calculations for the new boiler output you desire for viewing as undersizing a boiler can be a costly mistake

I couldn't agree more, however I am sure most readers would be bored stiff with detailed calculations of room sizes, volumes, U-values, etc etc!!

However I have just recalculated the figures as I discovered that the inner skin of the outside wall is Thermalite and not breeze block. This means that the heat loss, without cavity wall insulation, is 10.6kW and, with insulation, 9.1kW. This excludes hot water, say, 3kW. Which means that I will need a boiler of minimum 12kW net. I can see the sense in over-sizing - but not excessively.

 

[gas4you]

All this heat loss thing is a bit of a joke and a lot of effort with all these new fangled software programs about. Nothing beats the industry standard mears calculator, or at a puch the Stelrad stars program if you must do it on your pc

 

[DavidJW]

All this heat loss thing is a bit of a joke and a lot of effort with all these new fangled software programs about. Nothing beats the industry standard mears calculator, or at a puch the Stelrad stars program if you must do it on your pc

I thought I would check out both calculators you mention, so I did a google for mears calculator and eventually found their web site. If their product is the industry standard then the industry is still living before Industrial Revolution. Do they still use slide rules instead of calculators?

The Stelrad one looks impressive, but I doubt if it would come up with a more accurate figure than the Barlo one. After all there is a fair amount of guesswork involved.

When I get results which are all very close to each other from three different programs, I won't bother spending £45 just to confirm that I was correct!!!