DIY Doctor UK DIY Forums

The TRVs on my central heating system are old - 1980, perhaps. The actual valves are all working but some of the heads seem not to work properly, reacting very slowly or not at all to temperature changes. I assume the temperature sensors are wax which I have read tends over time to stop responding properly.

I'm planning on replacing them but other than being Honeywell, there is nothing to indicate the exact model - anybody know?

I've also noticed that different manufacturers/models of TRV head have different types of connection to the valve and different threads. If relevant/helpful, the OD of the thread on the valve top is 30 mm. And the pipes for the central heating are 10 mm.

Can anybody confirm what make/model of TRV head would be compatible with these valves?

What would people recommend to replace these heads?

Hi gwentlarry,
Suggest you buy the cheapest TRV you can find and see if it fits, if not try another one. The thread on the fixing ring must be the same but also the clearance to the actuating pin must be about right. You cannot assume that a newer type of Honeywell head will fit the existing valve bodies.
Regards S