rad btu's/boiler btu's

28 Feb 2005
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United Kingdom
I have an old Glow worm spacesaver 38000 btu, vented.
I would like to add a more couple of rads. The current rads equal about 36000 btu.
The question is can the boiler handle handle any more, what would happen if adding the rads took it to 39-40000 btu.
Thanks in advance for any help.
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Depends how the rad sizes were calculated. If they're exactly the size you need for say a 21ºC temp diff with resp to outside, you'll only get 19 or whatever. So you'll be fine 99% of the year.
No the calcs don't allow for hot water Kev. How much should I allow for this? Cylinder looks average size ( flat size if thats any help)
I don't have the hot water on that much ( its a small flat) so could I ignore the HW point?
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Mear's Calculator suggests

2.2 Kw for 130 litre cylinder

3Kw for 175 litre

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