Heat loss calculations

[Mark Tomas]

hi all.....I've just done a heat loss calculation and it's come in at 36 700 btu loss if that sounds about right!!! 3 bed detached bungalow..... question is please what size grant vortex external oil boiler do I require 21kw 26kw 36kw p.s in winter they'll be a 5kw log burner on the go.....thanks

 

[Dan Robinson]

37000BTU doesn't sound unreasonable, but you haven't furnished us with much information.

However, go for the closest output boiler you can.

 

[Mark Tomas]

hi dan (furnished us) ?? Please tell me more please what do you need to know.....

 

[muggles]

hi all.....I've just done a heat loss calculation and it's come in at 36 700 btu loss if that sounds about right!!! 3 bed detached bungalow..... question is please what size grant vortex external oil boiler do I require 21kw 26kw 36kw p.s in winter they'll be a 5kw log burner on the go.....thanks

36,700BTU is 10.7kW so all the suggested boilers are oversized. Are you looking at a regular boiler or a combi?

 

[Mark Tomas]

Hi dan oil combi 1 bathroom 2 people living only.....

 

[muggles]

What's your incoming mains flow rate & pressure?

 

[Mark Tomas]

Hi correction guys!!!! It's 42 000 btu not sure on flow rate and pressure but had 3 guys into look and all said exallant pressure when they turned kitchen tap and outside tap....

 

[JohnD]

in my house, the calculators say about 11kW

But on a cold night, or when heating the house from cold, it takes more. I would be chilly if my boiler only had as much power as the calculator says.

With my previous boiler, put in when the house was built, you could feel it cool down in cold weather when you ran a bath.

 

[John D v2.0]

Most heat loss calculators also include a warm up factor in the calculation to cover thermal mass etc. But you need to make sure yours has included that, otherwise you'll never hit your target temperature.
Same goes for sizing the rads.

 

[JohnD]

I used the Baxi whole-house calculator (now discontinued). As far as I can remember it measured heat loss calculated at a 20C difference.

I don't recall a warm-up allowance or recognition that sometimes the outside temperature is -15C.

In my own house I have upgraded radiator size and the boiler rarely needs to run at peak power.

 

[Dan Robinson]

don't recall a warm-up allowance or recognition that sometimes the outside temperature is -15C.

Why would it?

 

[JohnD]

because I want my house to be warm even on cold days So the 11kW result from the calculator would have been insufficient.