Testing 3 Way Valve

[Bonedry]

I think I've finally got to the end of my heating saga.

Split Tank
Banging Boiler
Pump wrong way round (own goal)...etc

Anyway before I started I had a problem in that HW only would work, CH & HW would work but not CH only.

It must have been like this since I hanged the old programmer (Honeywell?? Long binned) to a Sunvic select 207XL.

Anyway it needed a connection from CH OFF to the grey wire of the 3 way valve.

Luckily I had a spare core which could not have been used by the Honeywell programmer - I changed like for like.

Anyway during working this out I was getting 75 volts in places??

Now I've fixed it (I think) well I can have HV only CH only and HW & CH, I noticed when I checked HW & CH I got 240v on white and orange (correct) but 75 volts on grey?? Any ideas

Thanks in advance for any ideas or similar experiences

Cheers

John

 

[MANDATE]

yes! You have to understand how the actuator functions. there are two micro switches and when actuator approaches mid point it triggers the first but not the second. The white wire divides when entering the circuit board. You get a 240v one way and your 80v or so the other way.
When the switch is triggered it drops the 240v but leaves the 80v there to arrest the valve at mid point.
Triggering the switch also makes contact with the grey, so the 80v is back fed to the grey, but does not have any useful purpose.
If HW was off or satisfied then the grey is required to drive valve forward and it would carry 240v from either cylinder stat or programmer.
This in turn triggers second switch so the 80v is no longer generated, the orange wire then carries 240v to fire boiler in the CH only position.

 

[wilhelm]

Some one.years ago ,posted some crackin diagrams of how the three port valves work. ChrisR springs to mind, but I cant find 'em.

errrr..hope that helped...

 

[MANDATE]

A point I did not explain is with regard to the orange wire.
Although you have the 240v on orange, that also was backfeed. In the mid positon there is no power supply from valve out through the orange wire, that only happens after the second switch is triggered.
Because there is demand for HW, the boiler gets the 240v supply from the cylinder stat and it is back fed to the orange.

 

[Bonedry]

Gents

A big thanks!

I feel good tonight I've cracked and old existing fault!

Thanks again for the replies!

John