What size boiler?

5 May 2018
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United Kingdom
We have had several quotes to replace our Glow Worm Hideaway 70 boiler with a new condensing heat only one.

Sizes we have been recommended vary between 18kw and 30kw.

We have a 3 bedroom detached house with 14 radiators split between 4 doubles and 6 singles, plus 950 x 400 hot water cylinder in airing cupboard.

Is there an easy way to calculate boiler size as current recommendations have a wide disparity?
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Without knowing much about your property, I would guess at no more than 21kw. I base this solely on your old boiler having a 20.5kw rating.
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If the boiler you have provides adequate heating then choose one with a similar output power to the boiler you have. Input and output powers are different

glow worm 70b rating.jpg

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