Central heating still not working after 3 port valve replacement

[ErinBates]

A week back our central heating wouldnt come on, with timer or switched to constant.

The only way we could solve this problem was to run the central heating while the hot water was on and radiators worked fine.

Through reading a lot of forums online and asking a plumber, we thought it would be best to change the entire 3 port valve, which we have done today. As soon as we switched on the central heating it worked on it's own perfectly fine. Hot water on its own and both on together fine.

After 10 mintues of tidying up we thought it best to check all is still fine but now no central heating. Same as before.
We have tried bypassing the programmer by placing wire from live to hot water - this works fine but when trying to do the same with the central heating, nothing. Weve tried everything we can think of, checking orange and white wires no lives when CH on, checking thermostat on wall. Programmer lits up when CH on but no click to fire up the boiler.

No idea what to do now, please help!

 

[jackthom]

If White wire isn't live when CH is ON and the room thermostat is calling for heat there's likely a wiring problem.

Does the "Live" in the room thermostat become live when the programmer is set to heating only? If so, does the "switched live" become live when the thermostat is calling for heat?

Can you post a picture of the wiring centre?

 

[ErinBates]

Live wire doesnt become live when CH called for. Here are oictures of wiring centre, therostat wiring and programmer wiring

 

[ErinBates]

Also the hot water won't come on if we set programmer to all day, will only work with timer or 24 hours, we arent sure if this has always been the case though and weve only just now realised.

 

[ErinBates]

The thermostat doesn't call for heat when CH turned on. Is this a thermostat or programmer problem then? Hope to hear back its quite cold haha

 

[jackthom]

Sorry, I'm still looking at the pics but it's hard to make out the wiring colours and the connections properly in the uneven light.

Which model programmer and thermostat are they?

It's possible the programmer is getting a bit unreliable.


With Heating Only on the programmer.....assuming you have a multimeter, can you keep one probe on an Earth terminal in the wiring centre and then measure the voltages on terminal 8 and then 10.

 

[ErinBates]

We have ordered a new programmer that we can try but can only collect it tomorrow from screwfix, its the centaurplus c27. Thermostat is a Lifestyle. Its just strange that once we fitted new valve it worked but then when tried again after 10 minutes it didn't. Fingers crossed it IS the programmer, after changing valve and then that Im not sure what else we can do as all wires are through walls.

We did find that links between 7 and 8 were broken but weve fixed that and still no luck ill send a picture of the back of the cover plate too

 

[ErinBates]

Sorry here are better pics i hope

 

[jackthom]

That makes it a lot easier.

With the programmer on Heating Only, can you measure the voltage of terminal 9 in the wiring centre, which should be live regardless of the room thermostat setting..

 

[ErinBates]

We're getting 240V on 8
0 on 9
And 0 on 10

 

[ErinBates]

The hot water now seems to be intermittently working and then not working too. As soon as we took off the programmer we could power hot water through connecting with a wire but not the CH is that normal?

As soon as we put the programmer back on hot water works then turned off hot water, tried to put it back on and nothing.

 

[jackthom]

On the programmer backplate, wire links from Live to pin 1 and pin 4 together, should be equivalent to Heating Only.

Thats HW OFF and CH ON should be Live.

 

[ErinBates]

Oh my god thank you so much its worked! The heating is on constant now but can be switched off with room thermostat. Seeing as though this has worked does that mean we do need to replace the programmer?

 

[jackthom]

Yes it looks like the programmer may not be supplying the HW OFF signal when it should be.

I don't think an incorrect programmer setting would produce all of the symptoms you describe but can you just check it's set up for a "Fully Pumped" system and NOT "Gravity Heating".
That's the blue link on the rear which should still be connected.

 

[ErinBates]

Sorry how do i check if it is set up for a fully pumped system? Are you talking about the blue wire in the back of the programme?