What would be the longest run in 15mm from 22mm to rad without
losing any performance
losing any performance
15mm to rad
- Thread starter cosyslipper
- Start date
The limiting factor is the amount of heat (kW) being carried along the pipe. The more heat, the higher the flow rate of the water. This is given by the
equation: litres/sec = kW / (4.2 x temp difference), where temp difference is the difference between the flow and return temps. A 2kw rad will require a flow rate of 0.764 litres per second with an 11°C difference.
A 15mm pipe has a smaller cross section area than a 22mm so, to move the same volume in a given time, the speed (metres per sec) at which the water flows down a 15mm pipe will be faster than down a 22mm pipe. The higher the speed, the greater the friction and noise generated. On the other hand, if the speed is too low there is a danger of sludge deposits building up in horizontal pipes.
You can read more about it in Copper Tubes in Domestic Heating Systems and Copper in Small Bore Hearing Systems
The rads in question is a 600 x 1600 Double and 2- 600 x 1400 single and the boiler is a Potterton performa 28
That's about 5.6kW in total. 15mm pipe can carry a maximum of 6.5-7kW, so 15mm will be fine.
Thanks for the info
A 2kw rad will require a flow rate of 0.764 litres per second with an 11°C difference.
Can that be correct? It seems a lot.
Can that be correct? It seems a lot.
You are quite correct, it should have been 0.043 litres per sec. I calculated (2 x 4.2)/11 instead of 2 /(4.2 x 11). Pressed the wrong keys on my calculator!
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
