Too many radiators?

[scook17]

Is there a limit to the number of radiators you can have in a system? Can I run 9 rads from a 15mm pipe, if everything else in the house is 15m or microbore? I read in one of the B&Q leaflets you should only use 3 rads from 15m. I already have a bunch of 15m pipework to one rad, but to replace it with 22mm would mean ripping up the floor. What happens if I extend it and add the extra rads (8) I need? Do the rads just take longer to warm up or what?

Kind Regards,
Shane Cook.

 

[oilman]

I can't find the figures, but you could work it out Find the flow of water at a given pressure (from the pump). Allow 10 deg C drop across a radiator, and from the flow of water and 10 deg, calculate the power available. A radiator has a kW rating, so you can divide the power available by the chosen rads. Simple (not).

 

[scook17]

Or the simplier way of adding up all the radiators, and using 4.25Kw max for a 15mm run, and 10.5kw for a 22mm run. I actually found out the answer to my question, that is the rads only ever get warm, and not hot, if you put too many rads on a 15mm pipe.

Kind Regards,
Shane Cook.

 

[oilman]

.... 4.25Kw max for a 15mm run, and 10.5kw for a 22mm....

Great, those are the figures I couldn't find. What is the figure for 28mm, and where can I find the figures for further reference please?

Adding extra rads is useful for all the poor unfortunates who think they will get a payback period of 2 years for their new condensing boiler.