Motorised valve seems way too hot

[Doh!]

Bit of a puzzle with home heating - 18yr old 'Y' Plan system with 12 rads, one big and one small cold header tanks in loft and a hot cylinder with coil in first floor airing cupboard.
Two weeks ago heating stopped working - but hot water production still OK. For a few days following, if I moved the toggle lever on the Honeywell V4073A motorised valve from Auto to Manual it would fire up the boiler sufficient to get the rads warm - but then it would stop. I also noticed that the body/casing of said divert valve was incredibly hot ! Way too hot to touch. The valve is fitted snug up to the side of the cylinder (foam insulated) and I also have plenty of additional lagging around cylinder - including over the divert valve...so initially I thought this was the cause of high temp of outer casing.
So I bought a new Honeywell valve. Yesterday, I replaced just the motor part of the valve (not the 3 port brass and ball part) and everything returned to normal. System now correctly responds to all demands - hot water and rads all as normal. Room stat and clock all working correctly too. But....the outer casing of the new circular motor is, once again, unbelievably hot - way too hot to touch. Seems like the circular motor is running flat out the whole time - even when the boiler has not been on for hours. Is it in the process of burning up, like the previous one ?
Any ideas ?
One other clue (maybe)...when I had the old valve assembly off I manually moved the spigot shaft of the ball from side 'A' to side 'B' and back again, many times. It moves freely - spigot didn't seem stiff. When the pump was running the ball valve goes over with a thump in the pipes - as though the ball was making a good seal across the flow.

 

[Gasmk1]

On its way out could need a new head or could be struggling because valve is stiff you could just change the head and see if that cures it if it doesn't you will need to change the body. Which will mean a drain down I would advise a plumber/heating engineer to diagnose and rectify unless you feel confident enough to tackle

 

[moonlight]

When you changed the head, did the valve body spigot move easily? New top could be struggling with a sticky valve.

 

[Stigster]

With the head off the 3-port valve you should be able to move the spindle between its positions using just two fingers. It should move very easily. If it sticks then moves, feels kinda gritty or you cannot move it by finger power alone, the body of the valve is shot and the resistance is causing the motor to struggle and overheat.

 

[SJB060685]

When CH was last port of call then the motor is held open, obviously gets hot as a result

 

[Doh!]

Bit of a puzzle with home heating - 18yr old 'Y' Plan system with 12 rads, one big and one small cold header tanks in loft and a hot cylinder with coil in first floor airing cupboard.
Two weeks ago heating stopped working - but hot water production still OK. For a few days following, if I moved the toggle lever on the Honeywell V4073A motorised valve from Auto to Manual it would fire up the boiler sufficient to get the rads warm - but then it would stop. I also noticed that the body/casing of said divert valve was incredibly hot ! Way too hot to touch. The valve is fitted snug up to the side of the cylinder (foam insulated) and I also have plenty of additional lagging around cylinder - including over the divert valve...so initially I thought this was the cause of high temp of outer casing.
So I bought a new Honeywell valve. Yesterday, I replaced just the motor part of the valve (not the 3 port brass and ball part) and everything returned to normal. System now correctly responds to all demands - hot water and rads all as normal. Room stat and clock all working correctly too. But....the outer casing of the new circular motor is, once again, unbelievably hot - way too hot to touch. Seems like the circular motor is running flat out the whole time - even when the boiler has not been on for hours. Is it in the process of burning up, like the previous one ?
Any ideas ?
One other clue (maybe)...when I had the old valve assembly off I manually moved the spigot shaft of the ball from side 'A' to side 'B' and back again, many times. It moves freely - spigot didn't seem stiff. When the pump was running the ball valve goes over with a thump in the pipes - as though the ball was making a good seal across the flow.

When CH was last port of call then the motor is held open, obviously gets hot as a result

Thanks to all who replied and apologies, I don't know if I've pressed the correct 'reply' button...but just summing up all replies....I have already replaced the head, and CH/HW is working ok now (for the time being). The spigot did move the ball valve easily, by 'easy' finger pressure, across from A to B ports and back (no resistance or sticking) and also a good solid sounding "thump" in the pipework when I moved the spigot while the pump was running - which I assume indicates that the ball is making a good seal in the ports? But still, this morning, with the outer metal casing off the head, trying to touch the circular metal cover of the motor is like touching the sole plate of an iron set to 'low'- ie, it's way too hot to keep your fingers on for more than a second. Judging by the very feint whirring sound it seems like the motor is turning constantly - even though it was at least 2hrs since the boiler last fired up. I'm assuming the standard mode of operation is that the motor should only spin for a limited time - like when the pump is running ? Could it be that the head is getting a false signal from somewhere to keep spinning constantly ? If so, where could that faulty signal be coming from - the boiler, or the pump or ..?
Thanks again for your help - most appreciated.

 

[SJB060685]

It's a Y plan, that's how these work. It's not a false signal, it's how its wired internally

 

[garygvl]

as previously said the only time that motor wont get hot is in the summer months when you have no heating on and it doesnt have to do anything. during the winter months its most likely that motor will be in mid position or full heating position with the motor energised and the spring return trying to pull it back to hot water position. It's the drawback of a 3 port mid position valve. If , which is most likely, the last demand of the day is heating that motor will be powered up all night till the morning then is only likely to go back to mid position to do heating and water at the same time. It is possible for that motor to be powered up for the entire heating season. Its told what to do by the programmer, room stat and cylinder stat not by the boiler or the pump

 

[Doh!]

As I feared, the new head seems to have failed this afternoon. I'm assuming the motor burnt out, like the one before.
The boiler still fires up to make hot water but won't respond to any signal for heating. This time the toggle lever can't be manually pushed across - it seems locked solid in mid position. The head's been running so hot it's completely melted the red plastic covering of the tank jacket.
Tonight, I took the head off the 3port valve and turned the spigot (easily) by hand ....and hey presto the heating came on straight away. I can move it across easily - but is it safe to use it temporarily like this ?
Would welcome any ideas. I appreciate trades guys rightly saying "get a expert in" but apart from the satisfaction of fixing it myself the short truth is that we're in our 70's, this place is rented, and landlord refuses to fix anything. Out of necessity I've got used to finding other ways.
Many thanks for the replies.

 

[moonlight]

Did you unlock the head when you fitted it?

 

[Doh!]

Yes, I did unlock the head when I fitted it (I think) - if that means was the lever moving freely between Man and Auto, then yes, it was. But of course since the second head failed I've now removed it completely - so I'm switching the spigot by hand between water and heating. That worked OK for the first day - the boiler came on pretty quickly in response to where the hot water was needed. But now, although I can still move the spigot on the divert valve the boiler does not fire up in response immediately ? It can take hours before the boiler finally gets a signal from somewhere to fire up.
Any idea what's going on ?

 

[moonlight]

Your boiler wont fire for heating unless the valve switches over. The default setting is hot water.
The only way you will get heating with the valve off, is to put the spigot in the mid position and turn the hot water on but that will only work while you need hot water.
View: https://www.youtube.com/watch?v=NzdSWUoTQhg

View: https://www.youtube.com/watch?v=M9DkNwVL4Dc

 

[SJB060685]

As Moonlight says above

 

[Doh!]

Apologies for slow reply - been in hosp...God bless the NHS (and their heating system worked fine too).
Just want to say a big 'thanks' to everyone who replied - really helped me understand how the motorised valve works. It seems to me that the core problem is with the little ball valve inside the brass 3way port. Although it can be moved easily on the spigot from A to B i'm assuming there's something else wrong that's causing the motor to constantly spin and burn out. We're in an extremely hard water area so I quess that's got something to do with it. Unless you guys have better advice I think we'll wait til the warmer weather comes and have someone come and swap out the whole thing.
Can anyone recommend a reliable/reasonable CH plumber in the Stafford area ?
Thanks again for all your help.

 

[Bobblehead]

Apologies for slow reply - been in hosp...God bless the NHS (and their heating system worked fine too).
Just want to say a big 'thanks' to everyone who replied - really helped me understand how the motorised valve works. It seems to me that the core problem is with the little ball valve inside the brass 3way port. Although it can be moved easily on the spigot from A to B i'm assuming there's something else wrong that's causing the motor to constantly spin and burn out. We're in an extremely hard water area so I quess that's got something to do with it. Unless you guys have better advice I think we'll wait til the warmer weather comes and have someone come and swap out the whole thing.
Can anyone recommend a reliable/reasonable CH plumber in the Stafford area ?
Thanks again for all your help.

Hi came across you post searching for possible solution to MV head overheating. Third new 3PV installed in Jan and actuator head looks like it’s failed already being so hot. Did you get to bottom of your issue? Seems I have similar problem to solve. Thanks