On 10/03/2017 20:35, Bill wrote:
In message , John
Rumm writes
On 08/03/2017 10:07, Bill wrote:

For once this is my problem rather than sons or daughter.

Our central heating appears to be a basic S-type system with a Vaillent
Ecotec Plus 428 boiler, Siemens RWB2E timeswitch and RCR10 wireless room
stat. 2 Zone valves, one for CH, one or hot water. All installed by a
local company about 10 years ago.

Because of my persistent bad back, I don't feel safe climbing into the
airing cupboard and measuring voltages after taking covers off the boxes
there.
I have reset and checked the 2 controllers and all lights come on as
expected as dials are turned.

For about 5 days now the heating has been staying on all night. I've
been looking at the diywiki site and can't see how, with the stat and
timeswitch set to OFF, the system can be running. I can't believe that
both timeswitch and stat could have both failed at the same time.

Is there something I'm missing?

Possibly...

Have a look at:

http://wiki.diyfaq.org.uk/images/0/0d/S-Plan-Wiring.gif

Note that the grey wires to both zone valves is permanently connected
to live. Hence if for any reason the valve caused to be in the "open"
(i.e. heating on) position, then its internal microswitch will output
a call for heat on the orange wire to the boiler / pump etc.

So you have two possibilities; One, both the programmer and the stat
are erroneously calling for heat all the time (seems unlikely), or
two; the CH valve is physically stuck open (or at least its
microswitch is stuck in the activated position), and hence if feeding
a spurious call for heat to the boiler even when the programmer / stat
are not requesting it.

The fact that the rads are getting hot would suggest that the valve is
physically open - rather than it just being a switch or wiring fault.

My guess would be the valve body (i.e. the wet bit) has become stiff,
and hence the spring in the motor head is not strong enough to pull it
to the closed position when the valve is in the off state. The normal
solution would be to take the valve motor head off, lubricate the
shaft of the valve and twist it back and fourth while gripping it with
a pair of pliers. You may find that with the valve not energised (i.e.
programmer CH off), a few sharp taps on the side may free it.

Thanks, John, and the others who answered. I've been pretty slow because
SWMBO doesn't believe there is a problem.

I'm now pretty certain that it is a stuck zone valve, but with the
combination of its position and my back, I'm going to have to "get a man
in" to sort or replace it.

Taking a hammer to it failed, but was fun.

If you can reach it well enough to feel the manual lever that is on the
side of the valve, when its de-energised it should be held against one
end of its travel by the spring - as you move it by hand you should feel
resistance, and hear the gearbox / motor whirr as it moves. When you let
go, it springs back to the start.

If however its "floppy" and you can leave it at any position in its
travel, with no resistance to movement, then it is definitely stuck.


--
Cheers,

John.

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