Central heating playing up so I've been checking the valves. Two questions.:
1. The central heating circuit is controlled by a 2-port Danfoss valve.
I replaced the motor head a couple of years ago. I've taken it off and
got the heating going by turning the valve on manually. But I don't
think this motor is faulty - but i've forgotten how you fit it back on.
How is it done - what positions do the valve and motor need to be set
2. The hot water motorised valve is buzzing loudly (I thought it was
the Danfoss, but no). This is a 2-port Honeywell HF 002 body and is now
about 15 years old - is this one OK to take off and replace or is it
integral to the pipework (getting conflicting info about this).
OK thanks. I've now realised it's the old Honeywell that's controlling
the rads, so it does need replacing.
I can't get the Danfoss motor to respond though to the hot water
cylinder themostat or controller but as we have the hot water on all
the time I've left the valve open, and put the actuator on manual-open
and not refitted it. Not sure why it's not working.
If the central heating doesn't come on in the morning apart from me
being toast I'll have to get the cover off and see what's what.
You need to fix it because, in this position, the HW will be heated
whenever the boiler is running for the CH - and may got hotter than desired.
If the actuator doesn't move in response to the cylinder stat when
removed from the valve, either the actuator is faulty or there is a
Bear in mind that with an S-Plan system (which is what you appear to
have) the boiler will only fire when one or both valves are fully open
and operate their micro-switches. If the HW actuator isn't working, *it*
won't make the boiler fire - and you will rely on the CH actuator firing it.
If the CH actuator ain't working, it won't! If it's just noisy, it may
still be working ok. If it has opened the valve, the manual lever will
move freely with no resistance.
Roger - just a follow up question then:
So the hot water isn't coming on automatically.
It does come on when I open the valve manually with the programmer
switched on so I presume that's triggering the microswitch and firing
What is the best fault finding squence for this - the components are:
Hot water cylinder thermostat
Danfoss motorised valve
All wired into a wiring block.
I replaced the Danfoss actuator a year ago but at present the motor
clearly isn't active but I can't beleive it's gone after a year?
Does the motor move if disconnected form the valve body?
Best thing to do is to identify what setup you have from here:
Then follow the circuit through from the programmer end to the boiler,
with a multimeter and see how far the signals you need get.
So say you decide you have classic S plan wiring:
Start with the programmer calling for DHW on and CH off. Check pin 6 in
the wiring centre is live. Now rotate the cylinder stat so that you can
hear it click in each direction and check that pin 8 goes live in
sympathy with the stat position. Check the DHW valve moves in response
to the demand. Check pin 10 (orange wire out of the valve) goes live
when the valve is open. Check the call for heat goes live to the boiler
At some point in that procedure you will likely find something not
working. (often the valve not moving, or not moving enough to close the
microswitch that feeds a demand to the boiler)
Yes, that's a pretty comprehensive description of what the OP needs to
do. Chances are that the problem is with the actuator motor - even
though it's already been replaced - but it could be the programmer or
cylinder stat or any of the wiring. Following this sequence should
enable it to be diagnosed.
Does the boiler provide a controlled output to drive the pump? If so
a short in the wiring feedin the pump could do that.
 Many system will differ from the standard S plan wiring with the
boiler switching the pump supply itself rather than it being powered
automatically when the call for heat goes to the boiler. That way it can
do things like timed overrun.
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