Checking my calculations for adding radiators

[Bob Hill]

Hi all, I've just bought a house (Horray!) and thought it would a be good opportunity to practise my plumbing skills.

I'm hoping to add a few radiators as some rooms don't have any.

I've got a Greenstar 24i junior from Worcester Bosch - It's got 24kw heat output if i've understood correctly.

The WATTs for the current rads (1900x600, 1200x600, 700x600 and 1400x600) Adds up to about 5kw.

This means I should be able to add another 1200x600, 700x600 and a towel rail in the bathroom without any trouble according to my maths as the total would be about 3.5 for a total of 8.5kw leaving 15.5kw in the boiler to handle hot water.

Have I got it right? I'm doing level 2 NVQ at the mo and this stuff is level 3 as I understand.

Will adding more rads affect the hot water flow rate I can achieve?

On a side note I used an online boiler size calculator and it came out at 11.9 for my house - does this mean to adequately heat it I in theory need enough radiators to produce this amount of heat (the boiler is obviously big enough to provide it).

Thanks in advance!

 

[SafeGasInstall]

Adding rads is not a problem as long as you can make sure you can pipe size correctly the supply

 

[AWheating]

its a combi boiler right? if so the hot water and heating work at seperate times on demand and the output is never shared across the two.

each room should be calculated on its individual needs, either way your fine.

 

[Centralheatking]

yea aw is right - hot water energy loss does not figure for combis. so all the kws are available for your rads
the boiler stops doin the heating while makin hot water - via the dreaded diverter valve.

its only for conventional systems that you have to allow for heatin the cylinder up.

as regards rad sizes i must admit that 4 my own houses i fit oversize rads and turn them down or
really what fits and looks right or is chap cause its been hit by the forklift at our plumbers merchants !

got 2x 3.3 kw high output doubles for under a ton complete with covers last week -

centralheatking

 

[Bob Hill]

Thanks for the info so far.

I'm going to do the main flow and return loops in 22 and then drop to 15 for the last part to the radiators. That's how it's set up at the moment.

 

[stevetheplumber]

that sounds good bob you can get about 12000btus out of a pair of half inch so often the layout is 22 out of boiler split 22x22 up and down first tee on each level drops to half inch unless youhave a couple of big rads on the end of the runs then take 22 further