Y Plan Wiring Fault

[bewsh]

Got called to a customer today where the H/W was getting too hot and that the mechanical timer was losing time, replaced the timer, easy enough. But checking the operation of the mid-position valve, when you have heating only demand, the valve will only move to mid-position. Checking voltages and I was getting 240v on white, 0v on orange, and 68v on grey. I was getting 240v on the C/H on wire from the programmer.

If you put h/w on with c/h the valve moves to mid position, turn h/w off and it stays in mid position, turn c/h off and it springs back to water only, and if you put water only on, it stays in water position.

I removed the head of the valve and tested it also just in case the body was jamming the motor. Also I've replaced the valve head so can't be a motor fault.

The boiler won't come on with just a c/h demand, get 0v down orange until you put water on as well. And when you put water on as well, I was getting 80v on the grey.

The whole junction box was a complete mess connected to multiple different connector strips. I'm going back with a Drayton wiring center to re-wire it all so it's easier to work on. Has anyone got any ideas why the valve will only move to the mid-position.

Wiring is not my best strength, I must admit!

 

[ne1ls0n]

maybe a bad connection at the box not allowing enough volts through to move the motor?

 

[bewsh]

Cheers for the reply. But if I'm getting 240vac on the white, that should be sufficient to move it, shouldn't it? What sort of voltage am I expecting on the grey and white when both c/h and h/w are running?

 

[BLOD]

Check you've got a hw off wire from the programmer

 

[Ollieg]

Check you've got a hw off wire from the programmer

This is your problem. You need 240v on grey wire to fully motor over to htg only and send power down the orange.

 

[lame plumber]

have a read of this rather nice explanationHow the Y-Plan Mid-Position Three Port Motorised Valve Works | Electrician's Blog

 

[vern]

This is your problem. You need 240v on grey wire to fully motor over to htg only and send power down the orange.

This!

 

[diamondgas]

The grey gets it's power from one of two sources; hot water satisfied (Cyl stat NO) or hot water off from the programmer..! Room stat moves the valve to mid position only!

 

[jfb]

I agree you need 240v on the brown and grey wire. It must be a loose or damaged conection. You will probably sort it when you tidy wiring with new wiring centre.

 

[lame plumber]

more likely the heads knackered

 

[bewsh]

Cheers for all the replies guys. The cylinder stat that is currently there is an old switchmaster. So if that wasn't switching to satisfied then it wouldn't get the power for the grey? There is no H/W off from the programmer, should there be one?

I thought the head was knackered to begin with so I quickly chucked a new one on to check and still the same fault.

Cheers for that link as well, good read, bit more understanding of how the valve works now!

 

[sonray ltd]

Yes you need a hw off from programmer on a y plan.

 

[diamondgas]

Cheers for all the replies guys. The cylinder stat that is currently there is an old switchmaster. So if that wasn't switching to satisfied then it wouldn't get the power for the grey? There is no H/W off from the programmer, should there be one?

I thought the head was knackered to begin with so I quickly chucked a new one on to check and still the same fault.

Cheers for that link as well, good read, bit more understanding of how the valve works now!

If there isn't a h/w off then the programmer can not be programmed for heating only, there's nothing powering the valve from shared to heating only. The cylinder stat switching is easily checked ...

 

[bewsh]

Cheers for the info guys! I put a wire in from h/w off to the grey on the mid-pos and it worked a treat. I said to the customer that it must have had this fault since first installed and she refused to believe me (as they do) and apparently the fault has only been there for a couple of weeks.

 

[R1CKY]

Seen this many times, the fault won't ever show itself if the the heating and hot water are timed to come on together. Only when you run heating independently from the hot water will it show.