Replacing a TRV

[bobby55]

I want to replace just the top valve of a TRV on an upstairs radiator.

The exisiting one is an old danfoss with a black top, and the new one is also a danfoss but all white...RAS-C2 Combi

Quite a few years ago I changed just the top on a downstairs radiator without draining the system but have forgotten how I did it.

Is it possible to just change the top part, because the old one is covered in paint and marked and I prefer a nice clean one.

I have seen various threads on this subject but would like confirmation.

Thanks

 

[Charnwood]

There scould be a ring under the head. It just unscrews from the valve body (the head itself does not need to turn, just the ring.
Re-fitting is the reverse.

Most makes of head are the same thread and should work.
I've got a couple of Pegler Terrier TRV heads on Honeywell valves. Work perfectly.

 

[bobby55]

Is that the black plastic part directly under the white top, and if so do I need a spanner or something to undo it as I can only turn about 1/8th of a turn by hand.
I noticed that it has one recess on the underside of it as well

I have just found out that the top part I am referring to is called the sensor

Thanks

 

[bobby55]

Gordon Bennet, I forgot how easy it was to do!!!

Yes, turn the sensor to full on.
Then unscrew the knurled collar below the sensor.
Then pull up the sensor.

Thats it, the sensor was off and in my hand... :doh:

Fitting the new one was just as easy, but in reverse order.

 

[Charnwood]