The radiator is still warm when TRV is turned off

[rocksoccer]

Hi,
A few days ago, I turned off the water for my house from the main stopcock to replace a washer in toilet, because it is difficult to access the position to just turn that one cistern off.

But after I finished the washer replacement and turned the main stopcock on, some of the radiators begin to get warm when the heating system is on, even though the TRV on those radiators are turned off. Not all radiators get warm, only some of them, especially the ones in downstairs rooms. A couple of them even get as warm as the radiators that are turned on.

Before I turned off the main stopcock, just one turned off radiator gets a little bit warm. But now, there are quite a few.

I have tried bleeding all the radiators, and it did not help. And the radiators do not seem to have any air inside.

The boiler is a condensing boiler of ZB-7-28 R28 HE system. The pressure shown on the boiler is in the normal range, although after I turned the main stopcock on, I need to top up the water.

The central heating system is circulated by a LOWARA Ecocirc 25-4/130 pump, and the speed is at 3 (1~7). It seems there are some noises from the pump.

The tank is MEGAflo.

Does anyone know what is the problem? Is it related to the water pressure?

Thanks in advance

 

[ShaunCorbs]

The heating will still work even if the mains cold water is off

 

[rocksoccer]

The heating will still work even if the mains cold water is off

Sorry for confusion.
I mean all this happened after I turned off the main stopcock and then turned it on again.

 

[JCplumb]

So to sum up succinctly:
You have radiators that still heat up when the TRV's are turned down to zero?
Turning your mains water off shouldn't affect your central heating in any way.
TRV's aren't the most reliable way to turn off a radiator. The lockshield on the other side is.
Beware that lockshields can sometimes develop a delightful little drip when turned, depends on quality.

 

[rocksoccer]

I don't want to turn the radiators off completely. Some radiators are only occasionally used, so I just turned TRV down to zero.
I know TRV is not as reliable as lockshield, but it should still keep the radiator quite cool, shouldn't it?

 

[Chuck]

This will have been happening before you changed the washer in your loo, you just didn't notice it.

As TRV's age they often don't work as well as they did when new. They stick shut or fail to close. In practice, it doesn't matter too much it they don't completely turn off radiators as long as they significantly reduce the output as the room warms up.

It's time to replace the TRV when you walk into a room with the TRV and think "WTF? Why is it so hot/cold in here?". Change them earlier than this and you'll spend more on TRV replacement than you'll save on fuel.

 

[rocksoccer]

It is the problem of the TRV. I tried to push down the pin under the TRV head completely. And the radiator stays cool.

 

[doitmyself]

It is the problem of the TRV. I tried to push down the pin under the TRV head completely. And the radiator stays cool.

It could be a faulty TRV head, or the head may not be installed properly.

You can check if it's faulty by swapping with one which you know works OK. If faulty, you may be able to buy a replacement.

As for installation, it's important that the TRV head is turned to the highest setting (e.g Max or 6) when fitting the head. If you don't do this, the head may not screw on far enough to operate the pin. It also helps when removing the head.

 

[Ric2013]

I know TRV is not as reliable as lockshield, but it should still keep the radiator quite cool, shouldn't it?

Yes. And I would agree with post 8.