One Radiator not working...

[Dremon]

I have one radiator (bathroom heated towel rail) not working.
All other radiators work as normal. I also have a combi boiler, (Worcester 24i)
I once heard from a plumber that a "trick of the trade" and one they have to perform all the time, is to let the pressure out of the radiator, then turn the pressure back up using the boiler...? (Or something like that) I can't remember it exactly, but I've done this (right or wrong) and it doesn't change anything.
In fact when I try to bleed the radiator, there's a little air, followed by a little water and then nothing. I leave the bleeding valve openrolleyes and nothing happens.

Any ideas? The radiator is quite new, following a loft conversion, and used to work fine. Then it half worked - heated half the rail - and now (after I tried to fix it no doubt) doesn't heat a sausage...

 

[petej]

What pressure have you in the system ?
How high is the radiator above the boiler ?
If the boiler is on the ground floor with a water pressure of 1 Bar and the problem (loft conversion) rad was 10 mtrs higher you would have this problem.
For every 10mtr rise above the gauge you loose a 1 Bar of pressure
Try raising the boiler pressure to 1.5 Bar.
Pete

 

[SMR Bathrooms]

Sounds like the presure in the bolier is to low especally if this is a rad in the loft. up the pressure in the boiler and then bleed the rad, then check the presure in the boiler again.

 

[gissle]

Yeah,

There should be something on the boiler. Mine is a Worcester and there is something underneath which you can repressurize the system with, it's easy to do.

Also, in our previous house we had thermostatic valves on the radiators, they were locked off over summer and some of them became fused shut when it came to winter and we couldn't get these radiators to open up.

Tapping the end with valve gently for a while did alleivate the problem on some of the rads, but one of them was never quite right. I think it needed a new valve fitting really.

 

[SMR Bathrooms]

Okay, written this twice now and browser crashed twice, arragh!!!

Ignore my colleagues comment, pressure is not your issue. You have a balancing problem.

Pressure is an issue for water velocity and "radiator hammer" (it's actually the valve pin hammering, the radiator amplifying). This should not really be an issue if your boiler has been installed properly with an auto-bypass valve.

Balancing is a flow distribution issue. It normally occurs when new radiators are installed onto existing balanced systems (where every radiator warmed up). The addition often means that the furtherest/highest radiators from the boiler do not warm up. This is simply because there is insufficient resistance across the other radiators to force flow to these newer rads. You are unlikely to need more pressure, water just likes the path of least resistance, so if it can skip through a radiator on the 3rd floor instead of rising another 2 meters to another floor it will.

All radiators should be installed with a wheel-head and lock-shield pair. Naughty heating engineer if they installed two wheel-heads. A wheel-head is meant for people to adjust, a lock-shield is meant to be set by installer (for balance) and then is not easily adjusted again. Check out this little help page for more info http://www.smrbathrooms.co.uk/acatalog/what-is-there-to-know-about-radiator-valves.html.

Barring any quirks (not uncommon) with your heating system, the nearest radiators are on the ground floor, and the furthest on the top. To ensure every radiator gets heat, you need a well balanced system. The nearest rads to the boiler need more resistance (to counter-act the work done against gravity, and surface resistance to some extent, reaching upper floors) and the furthest ones need to have less resistance. It can be a case of trial an error, but you need to go around the house, set the nearest radiator lock-shields to one turn, the next level two turns, the next level three turns and so on so forth until you hit further radiator. The furthest radiator can be set fully open, because once the flow is there it doesn't matter how much you resist the flow now (unless you add a new even further radiator).

Hope this helps.