Sap and boiler sizing

[cully]

Please advise, my sap calc's for a new house states I require 4300kWh of space heating in the month of January (38.62kWh / sq. mtr)
If I reduce that down to the boiler working say eight hours / day then
4300x8 = 46kW
31X24
Is that what you would advise for a well insulated 600mtr.sq. house
It seems a bit excessive to me but I am not a qualified heating engineer
Thanks
ps I asked a question like this some months ago but cannot find it under search, keep getting "error"

 

[muggles]

You're multiplying where you should be dividing

4600kW a month
4600 ÷ 31 days in January = 148.4kW a day
148.4 ÷ 8 hours a day = 18.5kWh

 

[JohnD]

//www.diynot.com/diy/threads/htg-requirement-new-house.469333/#post-3756046

 

[JohnD]

4600kW (not kW/h) a month

eh?

 

[muggles]

eh?

Yep, possible brainfart moment there :-/ edited to correct

 

[cully]

Thanks for the input
With regards to the SAP statement (Page eight number 8 space htg. requirement from attach. sap below) it shows 4485kWh/mth
It must be the way I am reading it because it dosen't stack up, so probably you are right a "brain fart moment" (the up side is that I don't have many according to my wife!)
Back to the serious question with the info shown on SAP (around 4600kW space heating requirement) I would require a boiler minimum size of 18.5kW running at 8 hours to heat the house?
Thanks again also JohnD the link worked I was searching using the wrong key words

 

[JohnD]

OOI, I heat my house with gas, and in January, so far, it has used an average of about 7 cu.m per day, which is about 77kWh/day. It varies with mild winters and cold winters but this is typical. It looks like your average daily usage will be about double mine.

Your house will be different to mine, no doubt.

Energy from electricity costs about four times as much as energy from gas.

Note that the boiler runs at higher power during the evening and morning, when it's cold, and lower during the day, especially if it's sunny. It starts up at max power, which is 24kW, then eases off as the radiators come up to temp. I have oversized radiators to warm the house more quickly. You need more power to heat the house from cold than to maintain it once it's warm. The heat loss calculator says I need about 12kW. Your house is a lot bigger so will have much bigger numbers.

Builders like to cut costs by putting in small radiators, and this results in houses taking a long time to warm up, and being inadequate in particularly cold weather. Modern boilers (in most cases) have ample power, and modulate themselves down according to demand.