CH 3-port valves - what a nightmare
 

Despite being a clever design, they couldn't be more obtuse, could they?

I'm trying to work out why, this morning, the central heating came on
despite the timer control being set to off and the thermostat turned
down. Hot water was fine, I think, and the thermostat on the cylinder is
certainly activating the boiler when appropriate. Controller is standard
old thing with a timer and "off-cont-twice-on" settings for HW and CH.

I assume it must be the 3-port valve (Honeywell Sundial Y plan), but
once all the pipes everywhere are hot it seems actually rather hard to
test it without waiting for everything to cool down again in order to
see where heat is being delivered when I mess about with the controls.


If I think the motor has gone, then if I disconnect all the wires should
it stay in "how water only" mode?

Also, I can't find out what the manual override lever on the valve is
for!!! Is it supposed to set it to "heating only", "hot water only", or
"both on"??

Michael

CH 3-port valves - what a nightmare
 

In an earlier contribution to this discussion,
Michael Kilpatrick wrote:

Despite being a clever design, they couldn't be more obtuse, could
they?
I'm trying to work out why, this morning, the central heating came on
despite the timer control being set to off and the thermostat turned
down. Hot water was fine, I think, and the thermostat on the cylinder
is certainly activating the boiler when appropriate. Controller is
standard old thing with a timer and "off-cont-twice-on" settings for
HW and CH.

It sounds as if the valve has stuck in the mid position. When that happens,
the boiler will fire (and the pump will run) whenever there is a demand from
the HW stat - but water will flow round *both* the HW and CH circuits.

I assume it must be the 3-port valve (Honeywell Sundial Y plan), but
once all the pipes everywhere are hot it seems actually rather hard to
test it without waiting for everything to cool down again in order to
see where heat is being delivered when I mess about with the controls.


If I think the motor has gone, then if I disconnect all the wires
should it stay in "how water only" mode?


It depends on exactly what's happened. If the 'wet' part of the valve has
seized, nothing you do to the actuator (the electrical part) will make any
difference. If the actuator has simply got confused (and it *can* happen!),
powering it down completely - at the FCU which feeds the whole system, not
just at the programmer - may 're-boot' it and make it work properly again.
[If you need some help to determine which it is, come back.]

Also, I can't find out what the manual override lever on the valve is
for!!! Is it supposed to set it to "heating only", "hot water only",
or "both on"??

It moves the valve - against the return spring - to the mid (both on)
position, but not all the way to the CH-only position. It makes it easier to
fill the system with water by opening both circuits at the same time. If
it's working properly you'll feel quite a lot of resistance from the spring
and gears as you open the valve, and if you then let go of the lever, you
will hear the gears whirring as the spring closes the valve.
--
Cheers,
Roger
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CH 3-port valves - what a nightmare
 

Roger Mills wrote:


It depends on exactly what's happened. If the 'wet' part of the valve has
seized, nothing you do to the actuator (the electrical part) will make any
difference. If the actuator has simply got confused (and it *can* happen!),
powering it down completely - at the FCU which feeds the whole system, not
just at the programmer - may 're-boot' it and make it work properly again.
[If you need some help to determine which it is, come back.]


Also, I can't find out what the manual override lever on the valve is
for!!! Is it supposed to set it to "heating only", "hot water only",
or "both on"??


It moves the valve - against the return spring - to the mid (both on)
position, but not all the way to the CH-only position. It makes it easier to
fill the system with water by opening both circuits at the same time. If
it's working properly you'll feel quite a lot of resistance from the spring
and gears as you open the valve, and if you then let go of the lever, you
will hear the gears whirring as the spring closes the valve.

Thanks. In the end I'd guessed that it must be the mid-position as I
eventually discovered from info on-line that the spring defaults to "HW
only".

With regard to my faulty valve, I would have thought it would not be
possible to move the override lever if the valve were physically jammed,
but it moved (with resistance, as expected) and also returned with the
spring. Suppose it depends if the physical connection between valve and
actuator can break or slip if the valve jams?

I've cycled the circuit breaker in the fuseboard and I'll see what
happens...

Michael

CH 3-port valves - what a nightmare
 

In an earlier contribution to this discussion,
Michael Kilpatrick wrote:


With regard to my faulty valve, I would have thought it would not be
possible to move the override lever if the valve were physically
jammed, but it moved (with resistance, as expected) and also returned
with the spring. Suppose it depends if the physical connection
between valve and actuator can break or slip if the valve jams?

I've cycled the circuit breaker in the fuseboard and I'll see what
happens...

Michael

Did you test its movement with the lever *before* you'd cycled the power, or
not until afterwards?

If the latter, it could have been electrically 'stuck' in the mid position,
and cycling it may have cured it.

If the former, I suppose it's possible that there could be some crud lurking
inside the valve which is stopping the flap from closing off the CH port
completely - so that you still get some CH flow when only HW is selected.

Although unlikely, there's an outside chance that there's an electrical
fault which is telling the valve to go to the mid position when it
shouldn't. When this problem occurs, can you still feel resistance if you
move the lever, or does it flop about freely?
--
Cheers,
Roger
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monitored.. Messages sent to it may not be read for several weeks.
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