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I'm moving into a property this weekend that I used to let out in the past when I was a letting agent. It has a Glow Worm Ultracom 30Cxi combi and a Horstman 7 day prgerammable stat.
When I got keys the stat was dead so took it off wall and put on standard dial thermostat and that didn't work.
Now I'm ex Honeywell and know my way aruond a central heating system so got fault checking. No power to the wire on the wall, wire back to boiler seems fine, never been touched since installation so can't see why that would be an issue.
Opened up the panel and when i activate the heating there doesn't seem to be any obvious voltage coming from the board. I can't find a drawing that matches the PCB ecactly, but on my boiler at my current property there's two wires that go live when calling for heat.
The jumper wires have been removed and I know that that 'stat has previously worked for years.
Up rocks a plumber today to do CP12 thingy who says that it's only possible to activate the heating from the panel on the boiler, so wasn't interested in any fix.
I have a Curv smart stat i'd like to fit but need to remedy why this isn't sending 230v to the stat.
Otherwise the boiler works fine, used the timer on the boiler and it works fine, just doesn't seem to send power to the stat.
Could it just be a fault on the PCB?
Are you sure it's not a volt free signal ie resistance activated?
Power to the stat - some outputs to the stat are just a switch cable, in effect, so very little voltage goes down the 2 wires to the stat.
Go through the wiring diagram to make sure the cables are all in their correct postion, and make sure any jumpers are either in or out of the circuit board. ISTR some jumpers needed taking out to allow external control.
ISTR some jumpers needed taking out to allow external control.
That's how I successfully added wireless programmable stat and outdoor temp sensor. Easy with a diagram, but you won't be able to problem solve the correct settings as some have to be 'on' others 'off' to achieve the addition.
Things I'd check:
1. Is the central heating actually enabled on the boiler's programmer?
2. Is there a wiring problem (either a break in the cable or your tenants fiddling with it? You can test this by replacing the thermostat connections with a wire link at the boiler between live and RT.
Presumably there's nothing connected to the 24v side of the board (IIRC Gloworm will accept 240v, 24v and eBus controls but obviously not simultaneously).
Edit: older thermostats sometimes need a neutral connection to reduce hysteresis but should still work on a coarse level.
If the boiler works fine and the connection from the programmable stat to the boiler is fine then does this mean that simply your problem simply the power supply, or lack of, to the programmable stat? If so then why not just provide an alternative power source? Once the programmable stat has been reinstated or you've replaced it then it all should work fine shouldn't it?
If the boiler works fine other than the room stat then I'd go with a break in the wires to the stat somewhere. Realistically you could get away with not using those wires for the Curv. Wire in the receiver next to the boiler then the stat can be powered by USB until you find a way to get mains electric to it.