System heating up most but not all radiators

[shabbaranks]

Hi guys

Having a problem with a few radiators where they aren't warming up yet I can bleed them and water comes out 2 of the 3. Interestingly enough previously the one which isnt bleeding did bleed previously. The system hasn't been on for a while so I can't see what could the the problem especially as 2 of the 3 when bled water comes out.

Help is appreciated thanks...!!

 

[terryplumb]

Is system sealed/pressurised or fed from an F&E cistern ( small tank in the loft ) ?
Do the 2 radiators that bleed ok have TRV's ( thermostatic rad valves) if they do ,check the pin in the centre of the body moves freely up and down.
The other rad that doesn't bleed ,check the air bleed valve isn't blocked.

 

[shabbaranks]

Sorry should have said its a combi system so sealed and pressurised from the boiler. All of the radiators which are playing up have trv's. So I should be able to take the head off the trv and the pin in the middle of it should go up and down (guessing I cant damage it by pressing it down and it should slowly come back up?)

 

[terryplumb]

It should be in the up position once actuator head is removed,and should press down ,only a few millimetres,and spring back up when released.

 

[shabbaranks]

Ok cool and the otherside should that be fully open (obviously not fully closed) or half way?

 

[terryplumb]

The other valve ( lockshield) should be open to some degree. Its used to balance the system ,some may be fully open ,others partially to various positions

 

[oldbutnotdead]

Check the system pressure at the boiler if nothing is coming out of the bleed valve, you may need to top it up

 

[DP]

Ok cool and the otherside should that be fully open (obviously not fully closed) or half way?

Other side may or may not be fully open.
It needs to be set, in stages, so that you have 20 degree drop between the two pipes

 

[shabbaranks]

Guessing thats to give the radiator time to actually heat up?

 

[shabbaranks]

Is system sealed/pressurised or fed from an F&E cistern ( small tank in the loft ) ?
Do the 2 radiators that bleed ok have TRV's ( thermostatic rad valves) if they do ,check the pin in the centre of the body moves freely up and down.
The other rad that doesn't bleed ,check the air bleed valve isn't blocked.

Opened the air bleed valve a little bit to see whats cooking and it hissed a bit so you're possibly right she's blocked up. Will investigate that once Ive drained the system.

The radiators which aren't heating up I pressed down the trv pin and it popped back up so that seems ok. Any thoughts what else to test? They are all fed and returned from the same point as I extended the system. Could it just need a good flush to get things working well?

 

[terryplumb]

I assume the problem rads heated up perfectly well previously ,and no alterations have been made to any pipework. If this is so ,and both valves are open on those rads, try closing the TRV's on EVERY other rad ( don't touch their lockshields) run heating and see if problem rads now heat fully.
Why are you draining the system ??

 

[shabbaranks]

The system was never tested as we bought the house and then started renovating it, adding some new radiators and replacing the old. I was going to drain the system so I can take out the possibly sludgey air bleed valve and give it a good clean.

Just been given another tip (simular to what you said) turn off all of the working radiator trv's which hopefully will push the air and move to the ones which arent working so I can bleed them.

 

[terryplumb]

On rad that will not bleed,close both valves and slacken off the air bleed housing to reduce pressure ,then remove it and clear it or replace it. Always assuming the air bleed valve is within a housing that can be removed !
As the system has not been proven and pipework altered/ additional rads fitted ,it's also a possibility that they are not plumbed in correctly !!

 

[shabbaranks]

Ok cool thanks I will have a look as I just assumed (not being a plumber) and looking at the bleed valves they are one unit so you have to take out the whole thing but if you're saying some arent then I'll give it a go (Ive got some spare so I can have a look at them as an example).

And yes its quite possible that they arent fitted properly but I ran everything on the same runs (feed and returns) pressurised the system and it didnt leak also surely given the ones that arent heating up but do bleed with water (and had water in them when I drained it whilst working on it) are functioning all be it just not hot water

 

[terryplumb]

Show us a pic of the bleed valve.
A radiator will fill up with water even if both sides of it are connected to flow,or both sides connected to return, for instance , but it wouldn't heat up !!