Programmer/stat not controlling heating - trying to make sense of wiring?

[Jason90]

Hi,

My heating system no longer responds to the stat/programmer and can now only be controlled by turning the boiler down.

I've removed the front of the programmer (British Gas UP2, which seems to be a relabelled programme made by Invensys) and can see a pin missing - see first attached picture!

So am I right in thinking this is probably the cause of my issues?

And before I go ahead and replace this could someone please help me make sense of the wiring here? It's a Y-plan system, so is it normal that there are 2 wires going into the CH OFF terminal? (See 2nd pic)

Thanks in advance for anyone who can assist with this!

Jason

 

[Echo the husky]

No! The 'pin' missing is where the installer has cut it out so he can use the terminal as an extra one, If you were to replace it something boiler would likely run all the time the heating is switched off! You should fit the 2 black wires into a separate connector block if you are replacing the backplate as well.

What is the exact fault you are having? what can be controlled and what can't?

 

[Jason90]

Thanks, OK not as simple as I thought then!

A few months ago noticed that the boiler basically never stops going, no matter what the programmer or stat are set to.

The boiler seems to be working fine - getting hot water in the tank and hot radiators but we have to turn the manual temperature control on the boiler down to the "summer" setting to get it to stop burning...

Can't describe the issue much better than that!

System was fitted by British Gas. Boiler is a "British Gas 330" (manufactured by Glow-worm). Wiring has never been touched since they installed it.

 

[Jason90]

Also: there is a stat on the HW cylinder set to 50. This seems to be being adhered to as the flow into the cylinder cools down once the water is hot - so seems the issue is on the central heating side.

 

[Echo the husky]

Do you have a multimeter and know how to use it?

 

[Jason90]

Yep

 

[Echo the husky]

Good! Locate the wiring centre where the 3 port valve is wired back to and post a clear photo of the wiring if you can. With the heating and hot water off at the programmer, measure AC volts between the blue wire and orange wire of the valve.

 

[Jason90]

Hi. Cheers, ok...

I read 185V between orange and blue as requested.

Just to confirm I'm using meter correctly I got 230v between a random live and neutral!!

Full pic attached

 

[Jason90]

Leftmost black wire coming in is the 3 port valve. 2 greys next to it I have no idea. The next white cable along is the pump. And the very last white cable is the HW stat.

 

[jackthom]

While you measured that 185V was the pump running and boiler fired up? Its a bit high for an OFF condition and should really be 230V to get the heating going.

It would be useful to check the voltage for Heating ON, the white wire in terminal 4, again with respect to neutral. If it's permanently Live when heating has been turned off at the programmer it might indicate a duff programmer.

 

[Jason90]

Hi, yep it's 185 on the Orange with everything off, and 100 on the white. Pump not running and boiler not running.

Now I turned central heating on and kept hot water off at the programmer. Boiler set to "summer". Both wires read exactly same as before.

Now turn temp up on the boiler, pump is now running. Both wires still reading the same!

Finally, also turned on HW at the programmer. Orange now reads 238, white reads 80.

 

[jackthom]

So whether heating is on or off at the programmer the white wire still reads 100V ? How about when the programmer is removed from the backplate completely is it the same and does the boiler still run.

 

[Jason90]

Just turned the HW off again and left CH on at the programmer but turned it down on the thermostat so boiler should have stopped but carried on.

Pulled the programmer off the backplate and the boiler stopped immediately.

Edit: with programmer removed from backplate it's again 185 on the orange wire and about 100 on the white.

 

[jackthom]

Do you mean a room thermostat because I can't see where that is wired in.
Even if the programmer is playing up, the room thermostat should still be able to turn off the heating. If there is one fitted has it ever worked properly?

 

[Jason90]

Yes, definitely has worked in the past. It's in fact a WR1 wireless receiver. I can see the "heating on" light on the receiver go on and off as I alter the wireless room thermostat.

There's a wire going into it, and the wire coming out goes straight into the programmer backplate. So I presume that's why you can't see it wired into the wiring centre.