How do I work out the "BTU at 50c degrees Output" needed for a shower.
The size of one of the showers is 3070mm x 1700mm by 2400mm height.
Yaz
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To work out the size of any rad you need to know a) The U values of the walls, floor and windows b) The area of all walls and windows c) The temperature on the other side of those walls and windows d) The desired room temperature.
Then you feed the lot into a Heat Loss Calculator or similar computer program that works out the heat flowing into and out of all the walls. It adds the lot up and works out if you will need to heat (or cool) a room to maintain a particular temperature. It then calculates how much power that will take and spits out an answer in BTU or KW.....
...or you use your years of experience and guess.
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size of any rad you need to know a) The U values of the

How does one work out U Values?
>

Is there such a thing as a free calculater online?
Yaz
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wrote > To work out the

Sorry I think U values (UK) = R values(USA). ...
It's the thermal resistance. In SI units I think its measured in watts per degree K per square meter. You should be able to find tables for the particular construction you have somewhere.
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Yaz wrote:

Yaz-
I'm not exactly sure what you're trying to size (towel radiator?) or what you're trying to heat (a shower stall or an entire bathroom?)
In any case here is a link provided to me by "the all knowing Google"
http://www.hvaccomputer.com/gindex.asp
not free but pretty cheap for what it can do
On the other hand you could do an experiment & see how much heat input you need to heat your space
recently I had the need to keep a shower stall warm over night with the bathroom window open. I put a 100watt light bulb in the stall & it kept the stall at about 75F (the outside temp was about 58F over night.)
You could do the same but you'll either have to wait until the weather turns colder
or
ratio the heat demand by the indoor / outdoor temp difference when you do the experiment to the the indoor / outdoor temp difference for the coldest day expected.
The size bulb that keeps the shower warm is the constant heat input that would be required. I would double (or 1.5x) the heat capacity radiator so that it wouldn't have to run full open all the time plus it would give you some heating reserve if didn't choose a cold enough day.
BTW the heat output of the radiator would most likely be expressed in BTU per hour, watts or kwatts.
cheers Bob
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