no circulation on radiators, sealed system

[ara]

flat with 8 rads all on one level, sealed system, air lock in rad circuit (cylinder ok) Suspect pipe runs result in air being trapped in return leg, (filling loop is connected to return on cylinder), can't think how to clear it. changed pump but no improvement. Also have powerflushed system, just in case sludged, but actually was not too bad. very frustrated!

any ideas please. tks

[htg engineer]

Check system pressure is 1.0 -1.5 bar, Check pump setting and turn up if possible. Make sure all radiator valves are open and all radiators are full.

Turn off all but one radiator and see if this heats up, if it does try turning on radiators one at a time - then try all rads together.

Do any radiators heat up ?

[ara]

thanks for reply

yes, checked pump speed when i changed it.

pressure: have tried it on lower pressure, thinking it may help air come out or get into top of rads

then tried on higher pressure

someone has now suggested checking diverter valve paddle is actually turning

will try your idea of turning off all rads but one - the bathroom one gets warm.

it worked fine for two days after powerflushing

i am concerned over the filling loop connection to the old cold feed teed into return from cylinder

[pookie75]

I too have a similar problem. The only time my radiators work fully is when I've had the heating blasting on full 24hrs a day. I have had a corgi man visit and have the chemical in my header tank that is supposedly meant to sort the problem by flushing through any sludge but I have seen no difference in 3 weeks. I have tried turning all radiators off apart from the furthest away in the loop but it makes no odds. The pump has been inspected and I've been told that's fine. The heated towel rail seems to be the only hot rad in the house out of 7 in total. It would appear to be a problem with the circulation system as the return pipe is not heating up at all on the loop between radiators downstairs. I am very cold and no room is ever at room temperature. I am dreading my gas bill. If anyone can help please get in touch...

[ara]

Turned out to be faulty diverter/ zone valve. appeared to be working, but was in fact stuck and therefore allowing only minimal circulation, simple job to change and all fine since! Could have saved a lot of time and expense if thought of that first. Hindsight!

[pookie75]

Thanks so much for replying so soon. So whereabouts would this faulty diverter valve be in the system? Would it be something in the loft where the header tank is or in the airing cupboard or near the boiler?

[roger196]

Try the airing cupboard.