# Calculate BTU

• posted on October 13, 2003, 6:56 pm
Looking at getting the very old conventional boiler replaced with a shiney new combi boiler (Looking at Valliant ecoMAX combi).
1/ Anyone have any experience of these combi boilers? Are they any good?
2/ How do I determine my BTU to determine what size boiler to select? (3 bed semi, 7 radiators to feed).
Cheers.
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• posted on October 13, 2003, 9:26 pm
On Mon, 13 Oct 2003 19:56:56 +0100, Zapp Brannigan

Take a search on Google Groups. We have covered both subjects in depth before many times.
For the boiler, you will find that Vaillant are quite well regarded.
For the heat loss calculations look for terms like "heat loss" and also references to the radiator manufacturers like Myson, Stelrad and Barlo who have calculator programs to do the work.
I have also posted articles on how to do this by hand on numerous occasions. Don't use BTU as a search term though. This is a deprecated unit, and I certainly don't use it in calculations that I do. The metric and SI systems are much easier to use and don't involve funny conversion factors.
.andy
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• posted on October 14, 2003, 10:41 am

They are well regarded.

Except for very large leaky houses, even the smallest combi boiler will suffice for almost any domestic property not owned by a footballer or chief executive. The size of the boiler is high in order to provide sufficient instantaneous hot water. This requirement is usually very much in excess of the heating requirement for the house. A typical 3 bed semi would require about 5-15kW depending on the insulation levels. A combi is typically around the 28kW mark.
A 3 bed semi even with no wall insulation and a small layer of manky dodgy loft insulation would not trouble any combi boiler. Generally speaking, if calculations show that a larger boiler is required, it should be reread as stating that the insulation needs improving instead.
Christian.