Heat carrying capacities of cu pipe

[Bernie2]

The heat carrying capacity of copper pipe BS EN 1057 is

15mm = 10kW with a temperature drop of 11C and a velocity of 1.5m/s.

22mm = 22.14kW

It also varies with velocity the faster the more kW but usually 1.5m/s is the maximum and 0.3m/s the minimum.

But at 0.3m/s its

15mm = 2kW

22mm = 4.42kW

Quite a lot isn't it?

Google copper board "Copper in small bore central heating systems" it tells you there.

What use is it?

Well you get the heat output of your rad and it tells you what size pipe will suite.

So 3 - 5kW rads needs a 22mm supply, but you can reduce to 15mm after the first one as the other two only need 5kW each. In practice of course you have to take account of heat loss from the pipes as well.

But its a rough guesstimate rule of thumb way. Which being honest, if your motoring and people moaning at you, the stress is building, you ain't usually got much time for thinking things out in a leisurely way. So you want a quick way to do things.

Anybody add tips for the newbies?

 

[radswilldo]

on new installations its based on 20 degree differential, so capacities change.

 

[Bernie2]

Yes that's right. If your fitting a condenser the temperature drop is 20C but not if your fitting a system boiler or ordinary combi.

That work's out at 0.3m/s.

15mm = 3.63kW

22mm = 8.05

1.3m/s

15mm = 18.10kW

22mm = 40.20kW

As you can see with the bigger temperature drop the pipes can carry a lot more heat.

But don't forget if you have a temperature drop of 20C and use an ordinary boiler you have got to keep the return flow temperature above 55C, which means running the system at a minimum of 75C and above. Perhaps a bit warm for some.

If you don't of course, all that happens is that you get condensation inside a boiler not equipped for condensation, which means lots of corrosion.

 

[doitmyself]

Google copper board "Copper in small bore central heating systems" it tells you there.

Already knew about it! Another useful document is [URL="http://www.cda.org.uk/Megab2/build/pub-150-copper-tubes-in-domestic-heating-systems.pdf[/URL"]]Copper tubes in domestic heating systems

So 3 - 5kW rads needs a 22mm supply, but you can reduce to 15mm after the first one as the other two only need 5kW each. In practice of course you have to take account of heat loss from the pipes as well.

It's an eye-opener to calculate how much heat is emitted by uninsulated pipework. Fortunately most of it is not wasted as it is within the envelope of the house, so it contributed to the heating. But pipes under the ground floor and in the attic which are need to be insulated.

I calculated that the pipes in my house could be giving off some 6kW of heat. Unfortunately I can't get to any of them as they are either under the ground floor (carpet, underlay, marley tile, beam and block etc) or hidden behind the plasterboard inner skin.

As I have 13kW of rads and the boiler only produces 15kW, the rads rarely get up to temperature. Fortunately that is no problem as the house is well insulated.