Let me start by saying that central heating systems are a black art to
me. Ours is a conventional oil fired boiler supplying DHW and three
traditional wet radiator zones. Two zones are working, but the third is
not, and has not been used for two or possibly three years.
The zone valves are Honeywell, with a silver box on top, and having read
that the protruding lever should have resistance when the heating is
off, and no resistance when on, I have found the offending valve. There
are three valves in total, presumably one for each zone. Just one pump,
I've taken the top off the silver box (one screw) and can see the
actuator, but beyond that? Will tapping the actuator or the valve or
anything else release it? I guess it is stuck because it hasn't been
used. Can the actuator be changed without water pouring out?
If you select "images" after typing honeywell 3 port actuator into
Yahoo, it should make things fairly clear.
I believe the synchronous motor holds the valve position against the
stop by means of a constant "stall current" which affects the
reliability of the motor. The motor is available as a seperate item.
On Sun, 11 Sep 2016 13:43:49 +0100, Graeme
Well the simple test is to try the actuator whilst it is removed from the
valve and see what happens.
TBH if after removing the actuator, the valve spindle will not turn with the
help of a pair of pliers then that is your answer.
Let's go back to basics.
You say that you have identified the offending valve. Do you mean
that it should be powered, therefore open, and so should have no
resistance on the manual lever, but that it does have resistance,
indicating that it is still closed?
If so, can you move the lever against the resistance, thereby opening
the valve? There should be a little catch so that you can lock it in
the open position. Does doing this allow hot water through the zone?
If not, why do you think this is the defective valve?
Approaching this logically should give us the answer.
Do you have a voltmeter, and the ability to use it safely? I am not
being funny, I don't want you to electrocute yourself.
It does have resistance whether or not the system is calling for heat.
Yes! Why didn't I realise that? Anyway, yes, little catch locked, and
rads heating. I could live with that, at least for a while. This zone
heats four rads in what was our shop, attached to the side of our house.
The shop is closed and the space will be my 'hobby room', so remembering
to use that little catch to heat the place is acceptable if not perfect.
<grin> I'm no electrician but yes, I have a small multimeter, and can
use it for fairly straightforward stuff.
Which indicates that the actuator is not functioning, for whatever
reason, but the valve should be ok.
Good so far! Now we need to find out why the actuator is not working.
You will really need a wiring diagram at this point. I expect that the
valve and wiring look something like the one shown in the 'S' Plan:
This shows that the Brown and Blue wires are the power for the valve,
so IF you can get the probes for the meter to these terminals, you
should see 240 V AC across them. If they are unreachable, then find
where the wires go to, there will most likely be a junction box of some
kind within a few feet. Try there for the same thing, and report back.
shows various Plans.
If the lever moves back very slowly when released then the wet part of
the valve is OK
If there is 240vAC across the motor when the system is calling for
heat on that zone then the motor is shagged.
Does your valve have a removable head? The early ones didn't.
In either case I wouldn't buy a replacement head or valve, as the
synchronous motor is obtainable by itself. Generic ones should be
under £10 delivered, I think I got my last ones from BES.
If there isn't 240vAC across the motor then you need to look at the
thermostat and switches that are dedicated to that zone only.
Coincidentally, my boiler started to run yesterday, but stopped after a
few seconds. It did not run again all evening or night.
Today, I started by checking that it did indeed run of the CH was
turned on, which it did, so the boiler is ok.
Proceeded to do electrical checks, and eventually found that the
cylinder 'stat was stuck Off, I had to turn it all the way to max. to
make it work. It's now working, but I'll get a replacement. It's now
working, but I'll get a replacement, it's clearly not happy any more.
It's not always the valve!
Right. Removed the whole actuator assembly from the valve, and the
valve spindle turns easily. Held the actuator and applied power - I'm
assuming the actuator should actuate, but it didn't so either the
actuator is dead or there is a wiring problem.
There is indeed a nearby junction box and, within, the four wires from
the actuator are connected to a four wire cable which runs to the
programmer. The wires within the junction box are all neatly connected
and insulated, so cannot get probes in, to test. Would it be OK to cut
the wires, remove the four connectors and replace with a chocolate
block, which will fit within the junction box?
Personally, I see no problem, but I'm not a qualified electrician! What
you describe is how mine is done.
Can you find the other ends of the wires that feed the junction box, at
the programmer end, and check the wires for power there? That might find
a problem, closer to its actual location.
Or maybe test the wires at the actuator?
I reckon at this point that the actuator is probably dead, but it's
worth checking as far as possible first, just in case it's not that.
I went ahead without waiting for a reply. Five wires, not four, one
being earth. Anyway, now joined via a choc block and 240v indeed across
the brown and blue wires.
Tried applying power whilst the actuator was off the valve, and nothing,
so looks like a new actuator. Oh well, at least the wiring connections
will be easy, now.
Will report back when actuator purchased and fitted.
If you fancy taking it apart you may find that you only need to replace
the motor - obtainable from the likes of Screwfix for about 16 quid.
[Read the reviews for further info.]
Yes, I had thought about that, but the area just below the motor itself
seems stuffed full of little parts ready to ping around the room, never
to be seen again. I'll have another look, though. Having got this far
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