radiators only work when heating is on full!!

sallyt · 22 Mar 2008

hi,I have got aBaxi combi Instant 105e which is about 4 years old. All radiators worked fine up untill a few months ago. one of the radiators upstairs and one downstairs don`t come on at all unless the heating is on full.
we have bled them all and there is no air coming out just water. they all have thermostat valves on them but when they do start to work the top of the radiators get warm before the bottom and the valve end is the last to get hot, is this right

twgas · 22 Mar 2008

have you topped up pressure since bleeding rads, 1bar cold is about right.

some TRVs can go on return (outlet side of rad)

sallyt · 22 Mar 2008

we have turned all valves off except the two problem ones, we are waiting till they get hot and then we are going to turn heating off, then try bleeding. will wait till rads are cold to check pressure. don`t understand about the return valves can you explain further

twgas · 22 Mar 2008

TRV=thermostat valve.

don`t understand about the return valves can you explain further

the two pipes to the radiator are known as flow and return. flow is the inlet (gets hot first) return is outlet (sends cooled water back to boiler for reheating). Dual flow TRVs can be fitted on either the flow or the return.

Hope that helps

crockett · 22 Mar 2008

Also sounds like your heating system is dirty i.e. sludge build up. If it has been more than 3 or 4 years since the system has had a flush through and had inhibitor added to it, it's probably sludge..........

sallyt · 22 Mar 2008

hi, put pressure to 1(was .5)turned heating back on low went out and now we have come home the 2 rads in question were slightly warm(bearing in mind thermo on boiler is low). now turned boiler up high but rads not changed still warm even tho TRV`S are on 5.
stumped again now thought we had sussed it.............

sallyt · 22 Mar 2008

crockett said:
Also sounds like your heating system is dirty i.e. sludge build up. If it has been more than 3 or 4 years since the system has had a flush through and had inhibitor added to it, it's probably sludge..........

we did think that also but we have had the ladder rad off in the en-suite and the water was pretty clear, could it be the odd radiators I presumed it would be right through the system if it was sludge

gigz · 22 Mar 2008

Do you have a room stat (on the wall usually in the hall)

stardanny · 22 Mar 2008

Check the boiler pump speed. Might need to be rebalance system.
Did you have the boiler serviced? It may be a diverter valve seeping via DHW plate?

Dan

sallyt · 22 Mar 2008

gigz said:
Do you have a room stat (on the wall usually in the hall)

no thermostat except on boiler and on all rads(except 2 ladder rads in loos which are only at one temp depending on boiler stat

sallyt · 22 Mar 2008

stardanny said:
Check the boiler pump speed. Might need to be rebalance system.
Did you have the boiler serviced? It may be a diverter valve seeping via DHW plate?

Dan

hi , do you realise your talking to a woman here (no offence to any diy ladies out there) how the heck do I check the boiler pump speed. (do I need a plumber?? is it too advanced for a beginner

gigz · 22 Mar 2008

Try closing one valve on the ladder rads down. (close them and then open half a turn. See balancing in the F.A.Q. section.

sallyt · 23 Mar 2008

well , done the balancing thing and hey presto it seems to have worked, a massive thankyou to all who contributed. I cant believe how much I have learnt .......................thanks again

stardanny · 23 Mar 2008

Sorry, Sallyt.

I thought it would be too advanced for you. So it working ok. Good.

Dan

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radiators only work when heating is on full!!

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