Y-plan hot water but no heating

[jondub]

Hi,

My Y-plan system has today decided that it's only going to run the boiler when it needs to heat the water, but not when the room stat only is calling for heat. Thinking it must be the 3-way valve I replaced the valve head but it's no different.

I tried the valve in the manual position, I also tried it with the valve head removed from the valve body in case there was some mechanical problem but the boiler still doesn't light.

With the HW cylinder stat satisfied and the room stat calling for heat I get 230V on the grey and white wires to the valve, but only about 150V on the orange from the valve.

To me it looks as though the valve is still faulty although the head is new? FWIW the original valve was a Tower part, the replacement head I bought from Toolstation is a Corgi one but it seems to fit OK, wiring the same etc.

Any help appreciated!
John

 

[CBW]

Hello John,

Firstly check to see if that Corgi valve is compatible,if not swap it. Check your wiring to make sure all wires are making contact with the screws in the wiring centre.

 

[ianmcd]

but only about 150V on the orange from the valve.

you should have 230 v on the orange, has the valve motored to A

 

[jondub]

Hello John,

Firstly check to see if that Corgi valve is compatible,if not swap it. Check your wiring to make sure all wires are making contact with the screws in the wiring centre.

Thanks, the original Tower valve head is marked "22/28mm Mid position valve A3MID".

The Corgi part I replaced it with is "22/28mm Mid Position Valve Actuator A3MID-C", it certainly looks compatible. I'll double check all the connections.

 

[jondub]

you should have 230 v on the orange, has the valve motored to A

The valve does move but I'm not sure if it's doing everything it should. With both the room stat and HW stat set to low I get 0V on the orange. When I turn the room stat up only, the motor moves and I then get 150V on orange, but the boiler doesn't light. When I then turn the cylinder stat up as well the valve doesn't move (should it move back to mid-position?). I get 230V on orange and the boiler lights.

 

[ianmcd]

With both the room stat and HW stat set to low I get 0V on the orange

That is correct

When I turn the room stat up only, the motor moves and I then get 150V on orange, but the boiler doesn't light.

But does the valve move to position A ?

 

[jondub]

I'm not sure TBH, it certainly moves but how do I tell if it's in position A?

 

[ianmcd]

I'm not sure TBH, it certainly moves but how do I tell if it's in position A?

there is an indicator on the side of the actuator head

I'm not sure TBH, it certainly moves but how do I tell if it's in position A?

with the actuator removed, manually move the spindle on the valve body to be heating CH only and set the controls for CH only and see if the actuator and body line up

 

[jondub]

By indicator do you mean the lever that can put it in auto or manual? I can't see any other indicator on there.

With the room stat only calling for heat the lever has moved over to the right but it's loose so can be moved anywhere.

In any other state the lever sits roughly in the middle and can't be readily moved to the right.

I haven't been able to do the lining up thing because the actuator seems to need to be screwed to the valve body to work properly, with it removed although the motor is turning the gears don't mesh so the thing that turns the valve spindle doesn't rotate.

I've tried shorting out the room stat and programmer in case there was a high resistance contact somewhere but the boiler still didn't light.

Thanks for your help with this.

 

[ericmark]

The Y plan does not move the valve for DHW or send any supply through the valve, with the bleed lever going slack then valve must be going half way at least, but bleed lever only takes it half way so you don't know if going all the way or not.

The grey wire when powered makes it go half way only, and the boiler is powered from the tank thermostat, so in theory if grey wire removed and made safe then it should motor all the way, so I would try removing grey wire and see what happens.

 

[CBW]

Jon,

What @ianmcd means, is the letters are stamped on the valve body. Ab is flow into it, A to air (heating) B to Bath (hot water)

 

[ianmcd]

Jon,

What @ianmcd means, is the letters are stamped on the valve body. Ab I suspect flow into it, A to air (heating) B to Bath (hot water)

Only on the plastic heads , the one he has is a Honeywell copy they dont have the position indicator

 

[CBW]

Only on the plastic heads , the one he has is a Honeywell copy they dont have the position indicator

Thanks, however when I rad his original post, he said he’s got a tower valve , which going by the photos it’s stamped into valve body?

 

[ianmcd]

FWIW the original valve was a Tower part, the replacement head I bought from Toolstation is a Corgi one but it seems to fit OK, wiring the same etc.

 

[CBW]

Again mate, not dealt with many of these, so am I wrong in thinking that the lever moves to the sections labelled or is that for piping purposes only?