CH Motorised Valve Problem

[bert]

The Honeywell Motorised valve controlling the CH is sticking in the Open position so the heating is running continuously. In this condition there is no resistance when moving the manual lever on the head.

If I thump it a couple of times the valve moves and closes and switches off the boiler/pump. If I then try to move the manual lever resistance comes in when about half way across.

When hall thermostat switches on again the valve will work correctly and may switch off and on a couple of times but then sticks open again.

So am I going to have yet another lesson in Sods Law or will I be lucky and find its only the motorised head that needs replacing?

[The Natural Philosopher]

In general especially if there is hard water and not enough inhibitor these valves get sticky. You can remove the head and access the valve spindle and see if it turns smoothly and with little effort, without having to dismember the plumbing. Sometimes working it a few times manually clears a bit of blockage. Other times its is simply all gunged up and its a whole new valve.

[Davidm]

One of mine went like this and it was just the gear mechanism in the head that had worn and was jamming. A replacement head fixed it, but I waggled the spindle on the valve body a few times just to check it was moving freely. You can get a Honeywell compatible head for quite a lot less £££s, I'll see if I can find a link, but someone else might know.

[Davidm]

V4043 compatible head, see here

[Harry Bloomfield, Esq.]

bert was thinking very hard :

When in that position it is normal.

Again normal.

Yes, it needs a new actuator head. Sticking is what they eventually do, after a few years of use. The spring return type seem particularly prone to jamming after a bit of wear. I used to keep one on, one spare ready to fit.

You can buy a momo (motor on, motor off) type which does not use a spring return. The spring puts the mechanism under a lot of mechanical stress. MOMO's do a complete turn to the required valve position, in one direction, they are electrically more complex, so more susceptible to water leaking into them - but not a problem if the head is uppermost.

They are a direct swap electrically, but both head and valve need to be a match, you cannot mix and match.

[Harry Bloomfield, Esq.]

The Natural Philosopher submitted this idea :

The spring return type actuators jam, much more often than the actual valve. Easy to check- the D spindle of the valve should be able to be turned, almost with your finger tips if it is free. If not, work it back and forth a few times to free it.