In article ,
"MuddyMike" writes:
Our five year old Mexico HE36 gas boiler needs yet another auto air vent
valve. It was replaced in the final months of warranty due to it leaking and
dribbling water onto the electrics causing the trip to go.
Parts Centre are the only stockist I can find that have one, and one only!
Is in the Portsmouth branch but they are sending it up to me "next day"
delivery for four quid postage. That's not bad as it would have cost more
then that in diesel for me to have driven to the nearest branch

Anyone else aware of this being a regular failure on these boilers?

It's a regular failure of these valves. You can't leave them open all
the time, as the seal relies on being wet, which leaves an area which
will dry and form scale, and then no longer seal.

You may be able to recover it by flushing descaler through, although
it won't be pure scale, but mixed with other things in the heating
system water, so it might not work.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Sat, 04 Jun 2011 10:04:41 +0000, Andrew Gabriel wrote:

It's a regular failure of these valves. You can't leave them open all
the time, as the seal relies on being wet, which leaves an area which
will dry and form scale, and then no longer seal.

No, that's the fibre-washer type. Bottle type AAVs have a float which,
when it rises, closes a hole above it which (when there's air in the
system and the float isn't floating) lets the air out. It's the
suspension of the float mechanism that I referred to as dainty. These
types of AAV do usually have a sealing cap but these can usually be left
partially unscrewed to act as a dust cap whilst allowing air out.


--
John Stumbles -- http://yaph.co.uk

Thesaurus: extinct reptile noted for its wide vocabulary.

In article ,
YAPH writes:
On Sat, 04 Jun 2011 10:04:41 +0000, Andrew Gabriel wrote:

It's a regular failure of these valves. You can't leave them open all
the time, as the seal relies on being wet, which leaves an area which
will dry and form scale, and then no longer seal.

No, that's the fibre-washer type. Bottle type AAVs have a float which,
when it rises, closes a hole above it which (when there's air in the
system and the float isn't floating) lets the air out. It's the
suspension of the float mechanism that I referred to as dainty. These
types of AAV do usually have a sealing cap but these can usually be left
partially unscrewed to act as a dust cap whilst allowing air out.

It's the bottle type I'm refering to. The float seal will be wet
when sealing, which means there's going to be some moisture on the
outside of the seal, which evaporates and leaves scale. Eventually,
the sealing surface becomes contaminated with scale, and stops sealing.

I usually leave mine open for a week after refilling, and then close it.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Sat, 04 Jun 2011 12:22:08 +0000, Andrew Gabriel wrote:

It's the bottle type I'm refering to. The float seal will be wet when
sealing, which means there's going to be some moisture on the outside of
the seal, which evaporates and leaves scale. Eventually, the sealing
surface becomes contaminated with scale, and stops sealing.

The float seal may get wet and eventually suffer scale build-up if air
escapes vigorously causing water to spray out but I'd expect the rising
float to cut off the air escape port before the water level reaches it.
In theory of course: in practice whatever is in the water *will* get
everywhere and bugger it up eventually. :-(


--
John Stumbles -- http://yaph.co.uk

Who's *really* behind all these conspiracy theories?