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Clive Clive is offline
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Default ACL Lifestyle 2-port valves - maybe failed - how to override? NoDHW

Stuff about DHW failure and 2-port valves ...

Have you still got the problem, or have you fixed it?


More a "problem gone away" situation.
The Invensys Web site has a simple, and thinking about it obvious,
diagnostic routine. Basically shut CH and DHW to OFF and set
thermostats to low temp. The seperately switch on CH and DHW circuits
and turn at cylinder and room stat until see valves open, pump start
and boiler fire. This now happens reliably. At least I now have a
better understanding of how this all works.

What you have is a fairly conventional S-Plan system. See the S-Plan section
ofhttp://content.honeywell.com/uk/homes/systems.htmfor a schematic and
circuit diagram - which help to explain how it's supposed to work.

snip

If you're not getting any hot water, it almost certainly means that the HW
zone valve isn't opening, and isn't turning on the boiler and pump . This
might be for any of a number of reasons:
* Faulty wiring from the HW output of the programmer to the cylinder stat
and zone valve
* Duff cylinder stat
* Zone valve failing to open because of a duff motor in its actuator
* Zone valve opening but not turning on the boiler and pump due to a duff
microswitch [Not very likely because the HW would still be heated whenever
the CH is on]
* Zone valve failing to open because the mechanical part of it is seized.


All makes sense and a good checklist if the DHW goes off again


Armed with a mains voltmeter, you should be able to find out whether the
valve motor circuit is powered - and check back through the cylstat etc. if
it isn't. If it is powered, but still doesn't open, remove the actuator -
whilst leaving it connected electrically - and see whether that moves when
it's not on the valve. If it does, it's a seized valve. If it doesn't, it's
a duff motor.


Again - makes sense now.

snip

HTH!
--
Cheers,
Roger
______ To answer your question about over-riding the valve, the manual lever on
some valves opens the valve but doesn't move it far enough to operate the
microswitch - so the boiler still doesn't come on. I don't know whether
yours is like that. If you open the valve by rotating its spindle with the
actuator removed, that won't turn on the boiler unless the microswitch in
the actuator also closes.

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Ta

Clive