On Thu, 28 Jul 2005 11:16:35 +0100, Ben Willcox
wrote:

O.B. wrote:
My view too. You don't want the hassle of draining down the system
again because cheapo TRV has failed.

Hi Guys, interesting thread, I didn't know that there was such a
variation in quality on TRVs and have always just used cheap 5 quid
jobs. Just wondering what you all mean when you say they fail - I
understood that they all have a limited lifespan something do to with
the wax capsule or something, and therefore the heads will need to be
replaced after a number of years.
Is this what you're referring to? I don't get it as surely the heads
just unscrew and can be replaced without draining down? Or do the valves
fail too?

Cheers,
Ben.


Various failure mechanisms. Typical ones:

- valve body mechanism jams because of poor manufacturing tolerance
coupled with crud in the system.

- seal on valve begins to leak

- wax capsule fails and the valve locks on, off or simply has no
thermostatic action.


If you take a product like the Invensys TRV4, it has been available
for at least 25 years and the capsules last a good 7-10 years at
least. I have some that are 15 years old. You can buy the
replacement heads and swap them out. often it's cheaper to buy the
complete valve and not bother replacing the base.

On the cheap ones, failure usually means changing the whole valve,
base and all because often they have a proprietary fitting.





--

..andy

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