y plan problem

[wrinklyazza]

At job this morning y plan system but when put on heating and water off the neon on roomstat comes on when calling for heat but when you turn stat down it turns the valve off as normal but the neon on roomstat just goes dimmer and not off. tested at 10 way box and foubnd that there was a feed backfrom the grey off the 3 port valve feeding back down the white off the valve which was the feeding back to the roomstat hence why the neon was dimm on the roonmstat. Anybody got any idea how i can cure this
Only happens when on heating only and hot water off

 

[liam b]

change the valve head? should just screw off

 

[wrinklyazza]

its a honeywell v4073A valve do they just screw off

 

[ringer]

A diode would prevent feedback form affecting other parts of the circuit, but then that would only cure the symptom and not the fault. Depending on the make of valve, you could check the components on the little pcb inside the head. But then the cost of a new head is probably only £25 so might just as well replace it.

 

[Sparky20002]

Hi think should try replace valve head first - if honeywell/danfoss screwed onto valve base - if drayton (may be lucky) and clips on .

 

[ringer]

its a honeywell v4073A valve do they just screw off

Two screws, diagonally opposite each other, accessed through a cut-out in the motor-plate. Very easy job, but do not remove screw holding down motor by mistake, because that is the most visible one.

 

[liam b]

I can sell you one cheaper than any wholesalers if you want to make a few quid and charge the customer full price

 

[nickblake]

Check the wiring

 

[robsparky1975]

May sound silly but is there a hw on/hw off to the cylinder stat,instead of common/hw on as s plan would be,does sound like wiring although have found recently the microswitch in the honeywell valve to be jammed stuck(was an s plan though),last thing i expected,new unit,i went there to fault find,strange how its always the last thing you check that is the fault,but they can stick,so just an insight to look out for valves as others have said,i have had similar faults an phoned honeywell,the technical dept has people reading from books and they said to replace valve,no need in the end as i found and unstuck microswitch.

 

[emf]

This is not a fault as such the the valve outputs approx 100v under certain circumstances see Sundial Y plan reference guide Honeywell United Kingdom Heating Controls Towards the bottom of page 2

QUOTE=wrinklyazza;239470]At job this morning y plan system but when put on heating and water off the neon on roomstat comes on when calling for heat but when you turn stat down it turns the valve off as normal but the neon on roomstat just goes dimmer and not off. tested at 10 way box and foubnd that there was a feed backfrom the grey off the 3 port valve feeding back down the white off the valve which was the feeding back to the roomstat hence why the neon was dimm on the roonmstat. Anybody got any idea how i can cure this
Only happens when on heating only and hot water off[/QUOTE]