TRV not switching off.

[richie2305]

Hi, does anyone know why a rad TRV will not turn a rad off so it is always staying hot, I have read loads on the forum and the usual problem seems to be with them not turning on, the pin seems loose and free, and I have swapped the plastic head with another working one in case a bit may have snapped off and calls for max heat or something.

I then undid the bit with the spring/pin in and lubed with silicone grease, maybe a bad idea, but if it needs replacing anyway then I suppose it won't matter. Is there any recommendations for anything else to try please?

I am assuming the flow will be OK as a registered BG Engineer fitted the system before I moved in.

The TRV is a bulldog make, there is one on each rad 8 in total in a closed loop Combi system, the rest work ok, one is left open to max by the way to protect the boiler, I have also drained/cleaned the system which is 3 years old for another reason, so I am waiting on this action before I redrain again and put some more inhibitor in.

If as I suspect the TRV needs replacing, are the Terrier 2 ok, as they look the same, (from Screwfix), is there much difference between wax sensor or liquid sensor?

Thanks in advance for any suggestions.

 

[Agile]

I would suggest you hold the pin down and see if that turns off the valve.

Wax TRVs are much cheaper and respond in two to three times as long as a liquid TRV.

Tony

 

[richie2305]

Nice one I will try tonight, one thing I forgot to mention was the rad will turn off, but the TRV has to be turned almost completely off, well beyond the frost setting, and near the zero mark, and it is either on or off like its not even detecting the temperature changes, (like a lockshield valve would be).

Thanks.

Rich.

 

[richie2305]

I have tried another TRV top part, (the part where you adjust the temp setting), this seems to work, I can't be sure if it comes on and off on its own yet as it should but will find out.

I did notice that the plastic part which moves up and down inside the TRV top part sits on a different position on each valve, by this I mean on the one that works it is only a few mm away from the locking screw part (where it screws onto the angle valve), but the one which doesn't work seemed to be a lot higher up, so would never depress the pin down to close the valve.

I know my lack of correct terminology makes it hard to explain.

There seems to be no way of adjusting them either to make them the same as the valve is sealed, so it looks like I will have to buy a couple and use the top parts.

Woula adding a room stat say in the lounge help as at least that would stop them staying on?

 

[richie2305]

Does anyone know if the Terrier 2 TRV heads will fit onto an existing Bulldog valve, as I am sure it is the head that is faulty, (the bit that presses the pin is too far away from the pin, and is sealed inside so can't fix), if they do fit then that will save me having to replace the whole valve and drain the system.