Y-Plan Rads coming on when only Hot Water required. Help please!

[vintageaxeman]

Help required please!
I have a 15yr old house with a Honeywell Y plan.
Recently, in the summer with heating switched off, when the timer calls for hot water, and the wall thermostat downstairs is set very low, the radiators get hot too. It was as though the Honeywell V4073 valve was going to a mid position when only hot water was requested.
I have removed the valve actuator and tried switching h/w and heating on and off separately and together to see what effect this would have on the actuator, and it seemed to turn ok BUT made a horrible ratchetty noise at the end of its travel.
So I have just installed a NEW V4073 3-position actuator, but the problem unfortunately is continuing.


I am now wondering whether I need to drain down the system, and check the valve itself to see if THAT is faulty (ie the rubber ball has come off it's rod or something similar....)


Or could it be the timer has faulty relays?


I don't think it would be the wall thermostat or the cylinder stat, do you?


Has anyone else had this problem or can anyone offer advice please?


Thank you.

 

[TJ Anderson]

Think you have already sussed it but it does sound like valve is letting by. If the head is in the water only (sprung back) position and you are still heating the rads then it has to be the valve.

 

[Richard Burns]

It does sound like the valve passing.
If you operate the manual lever the valve should turn fairly easily (against the spring) if the lever is hard to move then the valve may be seizing up and not managing to close effectively. You can also turn the valve manually with the head removed and this can give a more responsive feel.
Sometimes just opening and closing the valve a few times can allow it to reseat correctly.

 

[vintageaxeman]

Thanks for the reply TJ....do you think it is possible for the rubber ball in the valve or the swing arm to become faulty / distorted or loose in 15yrs?

 

[TJ Anderson]

Thanks for the reply TJ....do you think it is possible for the rubber ball in the valve or the swing arm to become faulty / distorted or loose in 15yrs?

It is more likely that valve not seating correctly in the fully back position. As Richard has suggested, try operating the valve without the head, manually, through its full range and it may well cure it.

 

[Eco Chap]

Doesnt take much gunge and flux to clog those valves to be honest. The head will generally make that ratchety noise if its disconnected from the body as its travelling passed its natural end point (the cog ends up bouncing the arm back on its final pin a few times). As others have said if it was fine before most likely problem is the body of the valve.

Sent from my SM-G920F using Tapatalk

 

[vintageaxeman]

Thank you, all 3 of you guys!

You have all been really helpful!

I operated the valve manually a few times without draining the system, and it seems to be seating better.
The rads still get warm but nothing like as much as before.
The new head seems to be operating better too.
When I have to drain the system sometime in the future, I will probably change the valve body.

I so appreciate forums like this where folk are happy to help each other.

Bless you all!

Have a great weekend.