TRVs - Are the heads interchangeable?

[lavenders19]

I have a honeywell TRV that has been broken. Can i just replace the TRV element or do different ones have different depths, ie if the replaced one says 0, it won't really be on 0.

Many thanks in advance.

[Roger Mills]

If you replace it with one of the same make and model it will be ok. Otherwise, it may not even fit - let alone providing the right calibration.

[lavenders19]

I did think so. thanks for your reply. I will have to drain down and replace the full valve.

[Andy Hall]

There is a kind of industry standard based on a 30mm threaded ring and a plunger projecting about 5mm from teh valve base

I looked into this when replacing some Honeywell TRV heads with some motorised ones from Sauter. I suspect that it was originally Honeywell standard adopted by others.

However, other vendors don't all follow this because Sauter have a couple of adaptors for other major brands.

If it's a TRV4 head you can just replace the head - they are available, although for volume reasons, most plumbers' merchants seem to stock the complete valves at a lower price.

If the base is OK, you don't need to replace it even so. However, if the pin is sticky or crudded up, it may be worth swapping the base as well.

If you are going to do that, it's worth going round the house and checking all of them. The typical failure mode is that the valves become "binary" in operation - i.e. all off or all on.

[lavenders19]

Does this mean if I get a Honeywell head I will be ok with leaving the base???

[Andy Hall]

Should be. You could check the part number on the existing one and give them a call.

However, buying the whole valve including base may well be cheaper than the head only.

[TheScullster]

I recently discovered that the heads for the Drayton TRV4s vary. Those bought in shrink wrapped packaging from the sheds are taller than those bought from the local pm. Some of the height is between the connecting ring and the actuator so they are not interchangeable.

Phil