how to identify correct replacement thermostatic radiator head?

[jamin]

We have Pegler Terrier ll TRVs on all rads except one, which is a Terrier (but not a ll). All the ll's don't work correctly as plastic pin is too short for the valve - off is 0 and full heat is the only as far round as the * , 1-5 are useless as the plastic pin in the head is to short to reach metal pin of the valve. However the single Terrier seems to be fine as the pin is longer. It turns out someone came round a few years back and changed them all (bar one) and the TRVs have been knackered ever since. I cant be 100% certain what was there originally, I'm assuming the Terrier.

There is obviously a difference but how do I know what I want when replacing? Is a 'Terrier' the only replacement option as they seem very expensive compared to others! I need 20 odd so £10 extra is a hell of a lot (but cheaper than having the windows open as seems to be the cure at the minute!).

 

[45yearsagasman]

As I recall any trv will replace the Terriers. Try Draytons or Danfoss.
I do mean changing the valve body as well and not simply the heads.

 

[jamin]

Thanks 45 but I only want to change the head, all the valves operate correctly and with so many to change I want to keep the costs down.

 

[muggles]

You'll not get heads to fit those - complete new valves required