That's looking as though it's been wired correctly. Neutral is present. Do you know the model of the thermostat, do you have a wiring diagram? Worth checking the 3 wires are being tightly clamped by the screws.
I have a hunch that your live and the switched live are wired incorrectly- they need to be swapped over. I'm on a tiny phone ATM , need to wait until I'm home this evening on my mainframe. https://heatingcontrols.honeywellhome.com/documents/All/pdf/1008.pdf
Agree. Red is usually permanent live, should be connected to terminal 1 as indicated on the diagram on the unit. Yellow with brown sleeve is normally used as switched live (feed out to the load).
Hmmmm The electronic probe thing I have can't accurately isolate which is permanent live and which is switched. Presumably the switched feed is only live when the temperature is low enough for the stat to activate the boiler. Will need to get a 240v screwdriver type tester, so I can see what's happening. The whole thing only goes live when the controller switches the heating on.
Yes, with the stat wound down to the lowest temperature (which will 'open' the switch) you should see 240v on the red wire only. If this is the case then it is possibly connected wrong (it could be that the guy who wired it up used the yellow wire for the permanent live) You will find out when you dab a tester on it. Essentially the permanent live feed should be on terminal 1.
Now I can see what's going on- your stat has been incorrectly wired. The permanent live ( your red wire ) should be in terminal #1, and the switched live ( the yellow with brown sleeve ) should be in terminal #3. The effect of having them transposed is that the accelerator/heater component isn't coming into play, so although your thermostat is working, it isn't working as efficiently as it is able to. This is all assuming that your red wire is the permanent live, and the yellow with the brown sleeve is the switched live which is highly probable that it is, but for peace of mind worth doing the checks as Sando999 mentioned. That's what sometimes happens when you get plumbers fitting bits that should be done by an electrician btw!
Thanks but this was actually fitted by a pair of electricians subbed by the plumber. Not only that but this is the result of their second attempt. I don't remember the exact initial problem but it was much more fundamental than simply not switching quite as efficiently as it might. Couldn't get a neon light probe thingy in Halfords or PC World, which are close, will go to B&Q tomorrow.
Fitted it this afternoon. Mine had 4 wires on the old sunvic, a yellow, blue, red and earth that was attached to the metal mounting plate. blue and earth now lego bricked separately from each other so no longer active leaving the red and yellow. Batteries provide power for the display. Incredibly easy to operate, it shows you all the time the room temperature. You then simply use the up and down buttons to your preferred temp and leave it to do it's job. I normally turn the dial down to bottom measure of 5 when i don't want heating on and this will be easy to do too. definitely better as the old dial seemed to be 25+ for an hour or until you turned it down which mostly meant off. The new one is more stable and equal in it's accurate application of heat. I'll get a room thermometer to see just how accurate it is soon.
Ok, so purchased a more accurate Schneider probe, which has adjustable sensitivity and was able to determine that switched live was at Terminal 1. Have now swapped them and all appears to work as it should but I can't easily tell how much more efficiently. Thanks for all the help
