heat loss from pipework
- Thread starter ade2k
- Start date
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Oh no, they're much longer.
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A
ALEC1
given that all heating pipes should be with in a space to be heated how much heat the emit seems a bit of an odd question...
why do you ask..
why do you ask..
Heating engineers , on the big jobs , tend to lag pipes under floors even when the heat could be used in the room - e.g under a first floor in a ceiling . The answer to the OP question is - it`s variable , depending on the size of the boiler and the size/type/length of the pipe 
Maybe this might help - i am working on lagging the flow / return 22mm's to the cylinder and diverter valve etc, as in the summer the waste heat is not needed. Also they run through my uninsulated eaves space, so in the winter they run through a very cold space not to mention the risk of freezing.
Don't see point in lagging them up to the rads though
Don't see point in lagging them up to the rads though
It depends on the temperature difference between the water in the pipe and the air outside the pipe (Newtons Law of Cooling).
Assuming 75C water temp and 20C air temp, the loss from 22mm uninsulated pipe is 60W per metre and from 15mm is 45W per metre.
The loss from an 22mm pipe with 25mm thick insulation is approx 8W/metre; I don't have the figure for 15mm.
Calculators (e g, the online Whole House) usually assume about 5% for pipe losses, which I don't think is enough. Though it might be if all pipes were insulated up to the radiator.
A
ALEC1
well thats a different scenario...hot water primary and secondary pipes should be lagged as they have are for a different purpose from suppling heat to rooms...
The OP was asking a general question; he did not say he was asking about the DHW supply pipes.
Well according to my " Beeston Robin Hood " manual printed in 1947
As a general point ? the amount of heat given off by one square foot of heating surface atva given temp depends on the shape of the surface eg
1 square foot of pipe surface will give off more heat than 1 square foot of rad surface ?
With an air temp of 60 degs F & a water temp of 120 degs F one foot of 1" iron will emit 42 btu's per hour ( unlagged )
water temp of 130 degs temp diff = 70 degs between air & water same pipe will emit or lose 50 btu's
As a general point ? the amount of heat given off by one square foot of heating surface atva given temp depends on the shape of the surface eg
1 square foot of pipe surface will give off more heat than 1 square foot of rad surface ?
With an air temp of 60 degs F & a water temp of 120 degs F one foot of 1" iron will emit 42 btu's per hour ( unlagged )
water temp of 130 degs temp diff = 70 degs between air & water same pipe will emit or lose 50 btu's
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