one cold radiator

[kevkj]

hi, one of our radiators just went cold.
It is not fitted with a TRV.
When bleed, water comes out.
Both valves are open, and both pipes are cold.
The feed pipe runs through the loft, i have checked this and it gets warm halfway to the last radiator.
All othe radiators are hot, all are fully on with the return valve slightly open.
Any ideas ?? Thanks Kev.

 

[petertheplumber12]

Balancing radiators. (1) As a first step close any rads that are getting hot and see if that heats any of the other rads. You can quickly work out which rad heats first by letting them all get cold and when they start heating up find out which pipe gets hot first,mark it with insulating tape, use the pipe temp to test rad for heat it is quicker than waiting for the rad panel to heat up. (2) The radiators that are nearest the pump are usually getting hot first. First make sure system is on heating only no hot water and any bypass if fitted is closed. (3) If they have a lockshield valve one end and a hand control valve the other end, make sure hand control valve is fully open and then closed just a touch. Close the lockshield valve with a small spanner on the flats of brass shaft exposed when the plastic knob is pulled off, then open it 1/8-1/4 of a turn. (4) If there is a trv then make sure they are all open and the pins are up not stuck down. (5) Then move to rad that is next one from pump and repeat, and so on until you are downstairs then open lockshield valve ¼ -1/2 a turn. By the time a valve is open by 1 turn it may as well be fully open. (6) That should work all rads. Then open bypass valve to same position it was in. If you manage to get all the rads working, once the hot water starts heating it will unbalance the rads so set the programmer to heat the hot water continuous or hot water 1.5 hrs before heating. Good luck

 

[kevkj]

I have tried to balance the heating, this morning.
We live in a flat above a shop, the boiler is down stairs in the entrance. all radiators are upstairs. All are on, all returns slightly open.

 

[petertheplumber12]

Have you tried turning off all the other rads and see if that then heats it up,/ If it does then all the other rads need top be closed more than they are.

 

[kevkj]

I have turned off 2 radiators and it has warmed the feed pipe a little. But it is still not hot and radiator is still cold.
How has it suddenly gone cold ?
If we need to change settings to get it warm, why was it warm in the past ?

 

[sooey]

You say the feed to the cold rad runs in the loft. Is it lagged??

 

[kevkj]

The feed to all rads runs through the roof. They are all lagged. I have turned of 2 rads that are fed from a pipe that splits off from the main feed pipe.

 

[petertheplumber12]

I have turned off 2 radiators and it has warmed the feed pipe a little. But it is still not hot and radiator is still cold.
How has it suddenly gone cold ?
If we need to change settings to get it warm, why was it warm in the past ?

Balanced rads can change for various reasons, when I said turn off ALL the other rads that is what I meant NOT 2 rads. you need to prove the water will go to rad first. Then reduce the flow to ALL the other rads. Picture in your mind a pipe in the garden being fed by a pump, holes in the pipe fitted with smaller tube sticking up in the air, each small pipe has a tap all taps are open and pump is turned on. The water will squirt out of the pipe higher near the pump and not so high or not at all further away from the pump. Turn tap down on pipes near the pump and the rest is obvious. If you cant understand then get a plumber who can.

 

[kevkj]

Nice use of capitals, do you talk down to everyone like that, or just on the internet ?
Picture in your mind a pipe in the garden being fed by a pump, holes in the pipe fitted with smaller tube sticking up in the air, each small pipe has a tap all taps are open and pump is turned on. The water did squirt out of the pipe furthest away from the pump, nothing changes, but the water stops flowing to the end of the pipe. ?
I'm obviosly not as cleaver as a plumber. Thats why I'm on a DIY forum.

 

[petertheplumber12]

I use that method to emphasize a point and yes I do it verbally as it is infinitely better than swearing. I have tried to tell you that to prove circulation you must turn all the other rads off then one by one open them enough to get hot without taking too much water. And there are lots of plumbers who don't understand the principal of water circulating in a one and 2 pipe system, I happen to have been doing it for about 30 years so I have learnt a few things on the way.