By the sounds of it, the system ought to cope with your 600x600 (double panel?) radiator if it previously coped with a 600x1000 single panel. What happens if you turn off the bigger of the two radiators? Are you sure that it was fine with the previous radiator?
Basically, the bigger the radiator, the bigger the flow of water required to feed it. You sound like you have at least trebled the radiator power by going to two double panel instead of one single panelled radiator.
The pipes cause a resistance to the flow of water that the pump has to overcome. Unfortunately if you treble the flow of water, the resistance goes up by a factor of about 7 times, so your pump has to be able to work about 7 times harder.
Furthermore, even if the pump is sufficiently powerful, there comes a point when the speed of the water makes it noisy. The data sheet I have suggests you are slightly above the limit for an 8mm pipe.
Bear in mind I'm a physicist, not a plumber, who has learnt from problems with my own system. With my problem radiator the design had a 15mm pipe to it, but the plumbing contractors only fitted a 10mm pipe. I managed to just about solve it by really carefully balancing the system, but I also got an important 4C temperature improvement by flushing the radiator.
Best of luck
hoopyman said:
Steve__M said:
Is there any 8mm pipe left between the radiators and the boiler (it wasn't clear from your post whether you'd replaced all of it or just some of it).
I've had trouble balancing a system where I have a 1.8kW radiator (about the same as your 600mm X 1000mm double panel one I'd guess) on a 6 metre long 10mm pipe. My problem was no where near as bad as your problem, but an 8mm pipe is much too small for the amount of water required, and a 10mm pipe will struggle I thinkl.
Hi Steve yip the whole system seems to be made up from 8mm pipe the only 10mm pipe is from where I took the tee off so about 10 meters of 10 mm everything else is 8mm do you think I need to get a smaller rad then???