On Mon, 28 Mar 2005 22:28:15 GMT, "al"
wrote:

"Andy Hall" wrote in message
.. .
I've always used Invensys/Drayton TRV4s and had good results. In
general, I think that you could expect good behaviour from any of the
branded products like Honeywell or Pegler.

It's generally reckoned that the heads have a life of about 7 years.
I've never had less than about 12 from a TRV4 so am pretty happy with
them.

It is important in any case to have a clean system, so while you are
doing replacements, it is worth giving the system a thorough flushing
and filling with corrosion inhibitor.


And when they fail ...?




a



If you mean the radiators, then it was probably because inhibitor
wasn't used.

If you mean the TRVs, then making sure that the system is and remains
clean means that the plungers in the valve bases are less likely to
stick. Thus, when the heads do eventually go, it may well be
possible to just replace those.

I've found that the failure mode of the heads is generally that they
become hard on or off with no control in between.



--

..andy

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