I need advice with my central heating. Rads not getting hot.

[llChopperll]

I have a combi boiler in the downstairs cloak room heats the rad in that room and the first two rads on the 15mm ring upstairs (approx 4&5m from the boiler). The next rad (approx 9m from boiler) Fed from the upstairs ring but down stairs doesn't get any heat. Neither the next (approx 8m from boiler and upstairs). The flow and return on the ring isn't exceptionally hot here either. The final rad gets heat but not a great deal.

What can be the problem?

I've bled the radiators, tried balancing checked that the TRV's aren't sticking checked the motor (trying on all speed settings) and bled the whole system by removing the bleed valve completely attaching a hose and forcing the water through the system and checked no air in the motor itself.

Any advice would be much appreciated. I'm completely stumped

 

[45yearsagasman]

I'm completely stumped

So am I. It would be nice to know make and model. If its a combi as you say then the pump should be on 3.

 

[TeaTime]

Perhaps when you have drained the system, you didn't clear the sludge. have you tried running a chemical cleaner in the system for a while and then draining whilst it's hot?

 

[muggles]

If its all piped in 15mm is not surprising that it isn't getting hot.

 

[TeaTime]

If its all piped in 15mm is not surprising that it isn't getting hot.

Good point muggles.

Are you saying that your pipework for the central heating from the boiler is run entirely in 15mm pipework? Or do you mean it branches off the system in 15mm from 22mm?

You'll need to look at the outlet and inlet to the boiler and possibly under the floor, but youre CH system will suffer if the whole thing is run in 15mm.