Honeywell 3 port diverter snag?

[Harvest Fields]

If you have changed the head on the valve and you still have the same issue and the centre spindle on the body is moving freely, then it might not be the valve.

 

[John Armstrong]

If you have changed the head on the valve ........

I havent changed the head, just removed it for fault finding.

 

[Harvest Fields]

I’m now confused. Apolgies in advance if I sound rude. So you have changed nothing and still have them same issue?

 

[Johnm]

The motor is designed to be stalled on CH only and will be quite hot if powered up. In mid-position it runs via a rectifier to hold it static so it uses half power & runs cooler. Definitely worth checking whether the motor moves first.

 

[Johnm]

Timer? Sorry youve lost me...

Presumably you have a timer or programmer that turns both the HW & CH on & off. This would be in series with their respective thermostats. All need to function to make the valve work as intended.

 

[SJB060685]

As Johnm says. These valves hold last port of call. If CH was last the valve remains energised and in CH position, this leads to valve remaining hot and motor burning out over time. If HW is last port of call the valve would of spring returned to that port and hold. When HW and CH are called for together then the valve is held in mid position via a diode creating pulses of dc current to motor, this is enough to overcome spring tension but not enough to motor to CH only. With what you’ve said I’d be suspicious of the head. Probably best just to replace whole valve like others have said.

 

[John Armstrong]

I’m now confused. Apolgies in advance if I sound rude. So you have changed nothing and still have them same issue?

No need for apologies!
As you can see I am not a plumber, so I am checking first for easy stuff that I can do myself before calling in the experts:
I have removed the powerhead. It seems mechanically sound.
The synchronous motor is hot when powered so I am guessing that replacing that won’t help.
The spindle on the valve moves easily with pliers. I’ve lubed it. Does it move freely enough for the motor to turn it? Not sure.
Put it back together and nothing has changed.
Is the valve too stiff or is it something else?
Answers on a postcard please!

 

[John Armstrong]

With what you’ve said I’d be suspicious of the head. Probably best just to replace whole valve like others have said.

OK. Thanks, I see your logic.

 

[Harvest Fields]

OK. Thanks, I see your logic.

Hasn’t this been mentioned already?

 

[John Armstrong]

Hasn’t this been mentioned already?

Yes. So was this:

If it sticks again you can get a replacement ball valve and O-ring. It's part no "272752A/U CARD". Some draining down may be required, but it saves having to remove the valve body.

 

[SJB060685]

If the valve is sticking causing your problem of both CH and HW on at same time then there’s only so much you can do to prolong its life. Like I mentioned above as well with this particular design of valve the synchronous motor is likely to burn out over time leading to nuisance replacements. You’re best bet is to save time and money and replace the whole valve, be it you or an engineer. I personally don’t like these valves because of the problems we’ve mentioned, I always preferred an S plan but again they fail over time as well

 

[Johnm]

this particular design of valve the synchronous motor is likely to burn out over time leading to nuisance replacements.

The motor is designed to be permanently stalled. The motor is fed through resistors & a diode and my last valve failed because one of them had failed. I didn't realise that was the problem until after I had changed it to an S plan. Now have changed it back to Y on boiler mfrs recommendation to avoid need for bypass. If the spindle turns easily you don't need to replace the entire valve, just the motor or head. There should never be a long term demand for heat or HW.

 

[SJB060685]

What I meant John is if CH was last port of call then the motor will burn out over time. I know how the valve is held in mid position if you read one of my above comments. Am I wrong?

 

[Johnm]

When the CH is satisfied the valve should move back to midpos and then be held there by the rectified pulses. However, if there is a demand for HW it will unpower and spring would take it to HW.

 

[SJB060685]

This suggests to me that it’s last port of call is held and it doesn’t return to mid position. If I’m wrong then I’ve been wrong for years lol

 

[doitmyself]

These diagrams show what happens in the different positions. When CH only has been satisfied, the valve still stays in the CH only position due to voltage from the HW stat SAT or programmer HW OFF.

 

[SJB060685]

Like I said above @doitmyself

 

[John Armstrong]

Though this might be useful for diagnostics: I removed the powerhead then turned the supply back on (yes I put the cover back on the first!) Then turned on the CH/HW.

I can move the valve manually and I can hear it kicking over, so I’m guessing the valve is fine.

The powerhead isn’t behaving as it should, though I did wonder if that was because it isn’t physically attached to the valve?

My money is on a duff powerhead. What do you guys think?

 

[Harvest Fields]

I only ever change the heads first unless I know the body is passing, but then again I also have bodies on the van.

 

[John Armstrong]

I changed the powerhead.....
and it seems to have done the job. 😀