Help with temperamental motorised CH valve

[Laughton]

We have an S Plan heating system with 3 motorised valves (upstairs heating, downstairs heating and hot water cylinder). The valve for the hot water has become temperamental in that more often than not it fails to operate when the programmer and thermostat on the cylinder tells it to. So the valve doesn't open and we start the day with whatever tepid water is left in the hot water cylinder.

Just tapping the cover of the valve with my knuckle gets the valve to kick in and we're up and running again for the rest of the day.

What do people think? Is this most likely to be (1) just the little round motor inside coming to the end of it's life and needs replacing (how do I check) or (2) the little micro switch that tells the pump to start is sticking and I should just replace the complete valve or (3) the valve has come to the end of its life and I should just replace the complete unit or (4) I should just carry on getting up a bit earlier and knocking on the valve?

The valve is a Honeywell 2 port 22mm motorised valve.

Any help/suggestions much appreciated.

[Itsallaguess]

The valve is a Honeywell 2 port 22mm motorised valve.

It's definitely worth you getting a good handle on the different serviceable and replaceable parts involved in a Honeywell motorised central-heating valve, as a self-diagnosis or perhaps even a self-repair can often be easily managed by a competent DIY'er, so hopefully the following two videos will help with that -

How to fix a Honeywell Zone Valve - https://www.youtube.com/watch?v=1sIEdsybCQ8

DIY Repair Stuck Broken Heating Zone Valve Honeywell (No new parts) - https://www.youtube.com/watch?v=LQI_jnVjdEY

Honeywell valve part-numbers might be different, but there's usually enough commonality between 2-port Honeywell valves for these things to often be helpful and relevant.

A full valve-unit replacement is very rarely needed with these types of issues...

Cheers,

Itsallaguess

[pochisoldi]

Quick workaround
In the past when my HW valve failed, I did the following:
Remove the HW valve head, and set the HW valve itself to open.
Disconnect the "demand HW" lead from the HW motor feed, and connect it to the load side of the valve switch.
This means that the programmer HW output feeds into the thermostat, which then demands heat from the boiler.
(Note: If you have a wiring centre wired as per https://www.gassupportservices.co.uk/he ... al-s-plan/
then move the wire from the cylinder stat that goes into terminal 8 into terminal 10)

Note: You must move the HW valve to at least partially open, otherwise you'll end up with the boiler cycling on the boiler thermostat alone, and the only thing getting warm will be the bypass loop/valve.

I then flicked the option switch on my programmer to a setting which had "no CH without hot water" (so the HW and CH LEDs matched reality)
The down side of this is that whenever the CH is on, you are heating the water, but given that it's summertime and your heating is probably off, not an issue.

Permanent fix:
The valve head is usually* replaceable as a complete unit (done that myself in the past), however if the motor has failed/is tired then you can buy the motor separately - drill out the rivets and mount the new unit with nuts and bolts, and cutoff the crimp connections and replace with a 3A two terminal choc-bloc.
("Usually" means that if you don't have an early model of valve, you can split the valvehead and the valve without getting wet.
Isolate power, loosen cover screw, remove cover, two screws on diagonally opposite corners, bingo).

The google fu for the replacement part is "Honeywell synchronous valve motor"

For the record I replaced the whole unit in the past because I didn't know that the valve motor was available separately.

PS: Don't forget to reset the wiring back to standard, and switch the programmer back into standard "two channel" mode.

PochiSoldi

[bungeejumper]

How old is the valve? And can you see the model number? It should be on a plate at the side of the actuator. (If it's hard to see, a small mirror can help in these situations. Or just grab a pic of the hidden side of the actuator with your phone. )

Reason I ask is that some valves can have just the actuator replaced, and others can't. My old Drayton was like that, and I had to replace the whole shebang because the valve body didn't accept the new Drayton head unit. A few possibilities at www.amazon.co.uk/honeywell-2-port-valve ... valve+head.

If the head replacement will work for you, it's quick and easy. Good luck!

BJ

[Laughton]

Many thanks for replies.

I should have put in more details on my original post.

We've lived here 15 years so the valve and actuator are older than that and probably closer to 25 years old.

Yes, it does have a separate actuator head so I could replace that and feel confident that I could do it safely but it costs about £70 so in an ideal world I was hoping that someone would be able to say "Ah, tapping the cover making it work almost always means the problem is ......".

I also feel confident that I could just replace the motor - but if I end up buying a complete actuator head then that comes with a motor so would have wasted cost of motor if that's not the problem. I'm not so sure about being able to replace the micro switch if that is the problem, assuming it's possible to buy just the micro switch.

Appreciate the Youtube videos however one seems to be breaking down the actuator head assembly and the motor - knowing me that would take at least a whole day and I'd probably prefer to pay the £70 for a new unit and feel more confident that would give me several years more trouble free operation whereas my "repair" would result in cut hands and then waiting a week for a replacemnt to arrive.

A year ago one of the other zone valves failed, we started with replacing the head but that didn't work and ended up having to get a plumber to replace the valve too which meant draining the whole system which I hope not to have to do this time.

[bungeejumper]

Yes, it does have a separate actuator head so I could replace that and feel confident that I could do it safely but it costs about £70 so in an ideal world I was hoping that someone would be able to say "Ah, tapping the cover making it work almost always means the problem is ......".

Werllllllllll.......................... I've never had it, but it's not completely unknown for calcium deposits inside the valve body to make a valve stick. Do you have hard water? Any kettling from your boiler? What's the state of your Fernox?

Appreciate the Youtube videos however one seems to be breaking down the actuator head assembly and the motor - knowing me that would take at least a whole day and I'd probably prefer to pay the £70 for a new unit and feel more confident that would give me several years more trouble free operation whereas my "repair" would result in cut hands and then waiting a week for a replacemnt to arrive.

Quite right. Knowing how to put a cost on your labour and your poor battered hands is all in the game. Work it out, and then double it, because you'll probably have to do it twice anyway.

A year ago one of the other zone valves failed, we started with replacing the head but that didn't work and ended up having to get a plumber to replace the valve too which meant draining the whole system which I hope not to have to do this time.

Now we might be getting to the nub of the matter. If the valve you couldn't fix last year had been installed at the same time as the one that's playing up now, then it sounds to me as though providence is giving you a pretty hefty hint, no?

BJ

[Dod101]

Many thanks for replies.

I should have put in more details on my original post.

We've lived here 15 years so the valve and actuator are older than that and probably closer to 25 years old.

Yes, it does have a separate actuator head so I could replace that and feel confident that I could do it safely but it costs about £70 so in an ideal world I was hoping that someone would be able to say "Ah, tapping the cover making it work almost always means the problem is ......".

I also feel confident that I could just replace the motor - but if I end up buying a complete actuator head then that comes with a motor so would have wasted cost of motor if that's not the problem. I'm not so sure about being able to replace the micro switch if that is the problem, assuming it's possible to buy just the micro switch.

Appreciate the Youtube videos however one seems to be breaking down the actuator head assembly and the motor - knowing me that would take at least a whole day and I'd probably prefer to pay the £70 for a new unit and feel more confident that would give me several years more trouble free operation whereas my "repair" would result in cut hands and then waiting a week for a replacemnt to arrive.

A year ago one of the other zone valves failed, we started with replacing the head but that didn't work and ended up having to get a plumber to replace the valve too which meant draining the whole system which I hope not to have to do this time.

I too have three Honeywell valves. If this one is 20 plus years old, replace it for Heaven’s sake. It owes you nothing. In my experience the problem is seldom the valve itself (mind you, after 20 odd years…….) so no need for a plumber provided your are confident in replacing the actuator head ( the bit in the YouTube video) Do not start taking that apart just pay your £70 and get a new one.
Personally I usually call a plumber.

Dod

[jfgw]

If the Honeywell valve dates to before about 1985 and you try to take the head off, you might flood the place.

If it isn't that old, I suggest taking the head off. The spindle should turn freely by hand. If not, try turning it with pliers or an adjustable spanner. This may free it up if it is tight (but I would not consider this a permanent solution). What colour is the water? It is usually some shade of black if you don't have a magnetic filter. Some Sentinel X400 in your system for a couple of weeks or so before flushing and refilling with inhibitor might be of benefit if it has been neglected. Fernox F8 might be better but I am not as familiar with it.

Unlike most brands, the Honeywell heads do not work properly when removed from the body as the spindle is used to align the large cog. You could fit the head onto one of the other valve bodies if you need to test it and are doubtful about the hot water valve body.

I'm not so sure about being able to replace the micro switch if that is the problem, assuming it's possible to buy just the micro switch.

The microswitches are standard off-the-shelf components. I did replace one once but used a different brand and had to shave a bit off the button for it to work properly. A faulty one would not prevent the valve from opening, it would just stop the boiler from firing (and pump from running) unless one of the other valves was also open.


Julian F. G. W.

[BullDog]

Just replace the valve actuator head, extremely easy. But Google around for prices, they vary a great deal, often by 50%. And I recommend fitting original Honeywell, not a clone as there's a big difference in quality between Honeywell and cheap clones.

[stewamax]

Check first whether the Honeywell valve casing has a 1cm dimple on the front and at the opposite end to the power infeed and manual actuator lever.
The dimple means that the head can safely be removed off the spindle without needing to drain the system.

If the manual actuator lever moves slowly but smoothly to open the valve and when let go returns completely in 2 - 3 seconds, it is likely that a head replacement is what you need.
Replacing the synchro motor is much cheaper but is is possible that the head's limiter switch is sick instead so I myself wouldn't bother.

[Laughton]

Thanks everyone.

Sometimes you just need many voices telling you to do what you thought would be best in the first place - to actually do it.

New Honeywell head unit to be ordered in the morning (sometime after I get up to tap the faulty one).

[pochisoldi]

Hint: Don't bin the faulty head unit.
Keep it as a spare, or replace the motor and flog it for £50.

[DrFfybes]

Thanks everyone.
New Honeywell head unit to be ordered in the morning (sometime after I get up to tap the faulty one).

As BJ says, it could be the valve sticking just enough to overpower the motor, but probably not.

Remove the head, and test if the valve itself moves easily with a screwdriver. If so then replace the head.

Alternatively, buy a complete replacement valce, and swap the motor units over as a first step. This will mean you didn't waste £70 on the motor unit on it's own, and pretty much guarantee that the valve itself is fine so the spare will sit in the drawer until your family recycle it after your demise

Paul

[quelquod]

If the manual actuator lever moves slowly but smoothly to open the valve and when let go returns completely in 2 - 3 seconds, it is likely that a head replacement is what you need.
Replacing the synchro motor is much cheaper but is is possible that the head's limiter switch is sick instead so I myself wouldn't bother.

My own experience is that if the valve opens smoothly as above then 9 times out of 10 the motor will have failed - they often fail just enough to still move the valve but run out of oomph before they get to the microswitch. Replacing the motor takes 5 minutes - 10 if you drop a tiny screw and I always keep a spare beside the boiler, they’re only a few £s.

[Laughton]

My own experience is that if the valve opens smoothly as above then 9 times out of 10 the motor will have failed - they often fail just enough to still move the valve but run out of oomph before they get to the microswitch. Replacing the motor takes 5 minutes - 10 if you drop a tiny screw and I always keep a spare beside the boiler, they’re only a few £s.
Top

Ah, I can hear/feel the motor running so had discounted that but hadn't realised that it could run but not hard enough to operate the microswitch - and that would mean only changing over two wires. Now, I know I have a new one of those somewhere ..................... but where?