Diagnosing sticking motorised heating valve

[John Smith]

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?

[newshound]

To answer the first question, it is *possibly* a stripped gear on the
motor. These can usually be replaced and that should be straightforward.

Or it could be an actuator fault, they are also replaceable but someone
posted recently about a replacement which seemed not to be compatible.

Certainly whipping off the actuator for a look, and seeing if the valve
spindle moves is a good first start.

Are these two port or three port valves?

[Graham.]

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.

Graham.
%Profound_observation%

[John Smith]

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?

https://flic.kr/p/Qpt5cA

I can see the cover has a couple of screws - I guess that's the next step...

[Davey]

On Mon, 30 Jan 2017 18:41:42 +0000
John Smith <nos...@nospam.com> wrote:

> 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?

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.

--
Davey.

[John Smith]

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.

[charles]

In article <2017013018414222216-nospam@nospamcom>,

That's probably on the primary feed to the hotwater tank.

> https://flic.kr/p/Qpt5cA

> I can see the cover has a couple of screws - I guess that's the next
> step...

--
from KT24 in Surrey, England

[Graham.]

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?



--

Graham.

%Profound_observation%

[newshound]

See later post with picture, it's not two valves in series, it's an S plan.

[Roger Mills]

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.
--
Cheers,
Roger
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[John Smith]

thanks - very helpful. will have a good look.