Back feed with system off

[noddy997]

I seem to be getting a lot of backfeed with CH and HW turned off. 132v on white and orange on 3 port valve.

When CH is on demand I also get 240v on HW on cable to cylinder stat but HW is not turned on at programmer. Is this normal?

 

[RandomGrinch]

I seem to be getting a lot of backfeed with CH and HW turned off. 132v on white and orange on 3 port valve.

Here's a typical schematic of a 3 port valve in its resting position.

And heres a Y plan layout...

With no call for heat from C/H, or H/W, there should be no feed to either the orange, or white wires from the programmer.
There would be 230V on the grey wire, but given the resting position of the valve, there should be no "backfeed" to any other part of the circuit.
The voltage you are measuring (probably with a high impedance digital multimeter?) may be spurious, caused by cable capacitance, or wiring internal to the boiler.
If you disconnect the Switched Live wire to the boiler, does the voltage dissappear?

When CH is on demand I also get 240v on HW on cable to cylinder stat but HW is not turned on at programmer. Is this normal?

Yes, normal, with C/H only in operation...

Plenty of reading for you here...

Y Plan central heating system

Y-plan central heating system operation and wiring diagram

flameport.com

 

[Stuckinarut]

Do you have a Worcester boiler?

 

[RandomGrinch]

Do you have a Worcester boiler?

Vaillant ...

Ecotec 438, 2009 model

from another thread.

 

[noddy997]

It appears voltage is going to where it should except then pcb on boiler isn't kicking the pump on.... The brown wire in the green blocking was getting 0v. After testing it again it jumped to life.