Y plan fault.........................

[bigspark17]

no hot water.. getting live on white when isolated? Valve not letting heat into tank side of valve.. although messy other wiring seems fine.faulty mid position valve right?

 

[loplug]

The valve should give priority to hot water so that side should be open sounds like the valve has stuck and is back feeding to the white

 

[davesparks]

If anything is live when it is isolated then it surely is not actually isolated? Do you mean you have switched off the isolator and the white is still live?

 

[davesparks]

The valve should give priority to hot water so that side should be open sounds like the valve has stuck and is back feeding to the white

A Y plan uses a mid position valve, this gives a 60:40 split between DHW and CH when both have demand not DHW priority, a system using a diverter valve would give DHW priority.

Where would the valve back-feed from to cause these symptoms?

 

[davesparks]

no hot water.. getting live on white when isolated? Valve not letting heat into tank side of valve.. although messy other wiring seems fine.faulty mid position valve right?

Have you confirmed that the programmer and cylinder stat are switching correctly?

 

[loplug]

A Y plan uses a mid position valve, this gives a 60:40 split between DHW and CH when both have demand not DHW priority, a system using a diverter valve would give DHW priority.

Where would the valve back-feed from to cause these symptoms?

Sorry wrong terminology,When there is no power to the valve it should still be open to the hot water side. If there is power on the white when it is disconnected this could be coming from the grey back through the switch in the valve.

 

[bigspark17]

Have you confirmed that the programmer and cylinder stat are switching correctly?

I have with the valve isolated.

 

[bigspark17]

If anything is live when it is isolated then it surely is not actually isolated? Do you mean you have switched off the isolator and the white is still live?

The white wire was disconnected from the wiring centre while testing as i wanted to rule out backfeed. Seems like there is a problem within the switch,no power to either white ot grey should result in valve opening for DHW only.

 

[davesparks]

Sorry wrong terminology,When there is no power to the valve it should still be open to the hot water side. If there is power on the white when it is disconnected this could be coming from the grey back through the switch in the valve.

Surely for the grey to become connected to the white, the valve to be stuck at CH only and the white to be live when there is DHW demand microswitch 2 must be stuck on and microswitch one completely shorted between all three terminals?

 

[nunthe wiser]

Don’t deal with y plan systems often but Honeywell do 2 port valve with a white wire that is normally closed. Is it possible someone’s fitted the wrong head and your not being given all the information

 

[bigspark17]

Asked the plumber to change 3 port valve, will report back. Thanks for your help.