If a motorised valve is making a buzzing noise and not opening the central heating pipe is that likely to be just the actuator that's gone? The manual override works OK.
This is an intermittant fault. It's a Danfoss valve - is it straightforward to replace the actuator? Or best to replace the whole thing (which I can't do...)
Also, I see our system has two motorised valves in series - a Honeywell and the Danfoss - what does the Honeywell do?
Two 2 port valves plumbed "in series" seems very odd. Are you sure the pipe joining them together dosn't have a tee taking a feed from the boiler flow? That would indicate a standard S plan probebly.
Thanks - here's a pic - it's the white one on the right so a two port valve I presume (ignore pipe behind it). But what does the Honeywell on the left do?
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I can see the cover has a couple of screws - I guess that's the next step...
Well, it seems to me that they are on different pipes. Where do the three pipes involved go to/come from? That is, the two with the valves, and the one that feeds them. There is the 'T' to which Graham referred.
No - the Danfoss is on the horizontal pipe (ignore vertica pipe behine
- it's not conncted to the valve), and to its left there's a T to the Honeywell. I presume the Danfoss is the central heating on/off valve and the Honeywell controls the hot water.
Looks like standard S-plan to me. I'm assuming that the ?22mm pipe coming in from the left, the middle one of the three, is the feed from the boiler, which is then split two ways, down through the grey Honeywell to the DHW tank, which opens when the tank thermostat calls for heat, and horizontally through the white Danfoss to the CH system, which opens when the house thermostat calls for heat. The vertical ?22mm pipe on the left is a return to the boiler, leaving the ?15mm pipe running behind the Danfoss unaccounted for.
That's the right idea, although it could equally be the other way round, impossible to say from the picture.
Anyway I have a question about your pipework that someone with gas experience might like to answer. The top pipe looks like it's 22mm gas that reduces to 15mm at the elbow and goes through the wall to feed the boiler. But there is a tee in the 15mm to another appliance. Wouldn't that tee have been better placed in the 22mm section?
As others have said, this looks like an S-Plan system with the hot boiler/pump feed on the left, and then splitting into 2 circuits at the tee - with one valve for hot water and the other for central heating.
To answer the original question, you should be able to separate the actuator from the wet part of the valve by removing a couple of screws which are probably under the cover.
You can then check whether the spindle of the valve moves freely. The actuator doesn't provide all that much torque so even if you can move the valve with the manual lever, the actuator may not be able to move it if it is stiff. If is *is* stiff, you may be able to free it by rotating it backwards and forwards a few times with a pair of pliers.
While the actuator is off, you can check whether that works by calling for heat in whichever circuit it controls and seeing whether the bit which connects to the valve shaft rotates as expected, and then returns to the closed position when the demand is removed.
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