C/H Electrics Query - Programmer

[Butterfingers]

Hopefully someone can help me. This is my first post so sorry if I don't include all the information.

Yesterday my Sunvic XL C/H programmer made a loud buzzing noise and gave off an electrical burning smell before the digital screen went blank. I took the programmer off the wall, disconnected it and unscrewed the back. A resistor on the circuit board had cracked which I replaced. I put the programmer back together and re-connected it to the N, L, 3 and 4 connectors, exactly as they had been connected before.

The programmer now works but does not tell the boiler to fire and I can't work out why not. The boiler is an outside Warmflow combi and I have room thermostats, so the programmer is to zone my heating upstairs and down. Without the programmer the boiler continued to fire when the hot water was turned on but will not now fire for the heating. The pumps were working ok and the lights on the boiler show that it is switching between the DHW and CH pumps as it should be (with CH light always on when hot water is not being used).

I'm not sure whether the original short, could have affected the wires from the programmer to the boiler and how I could check this out, because it seems as though the programmer is not 'talking' to the boiler.

I have hot water but no heating and yet the programmer seems to be working.

Any help would be great - thanks

 

[electronicsuk]

Is there perhaps a relay on the programmer that provides the necessary switching for the boiler demand, that might have been damaged when the resistor failed? Or perhaps you need to be looking a little deeper, as the resistor failure could have been caused by another component on the board going short circuit. It's hard to say without seeing the programmer or a schematic, the above are just obvious things to check.

 

[Butterfingers]

Thanks Matthew,

Since my last post the programmer has gone again and despite opening it up, there doesn't seem to be an obvious problem with the programmer. Is it likley that the problem is with the programmer or with the wiring from the boiler to the programmer (probably an impossible question to answer)?

 

[JohnD]

you can buy a new programmer at modest cost

My local Wickes is selling end of range programmers at £5 to clear stock. I think their own-brand are rebadged Siemens.

Can you post a pic of yours, including the back? Does it plug onto a wall plate? If so, please show a pic of the plate - it may be an industry standard one in which case lots of other brands/models will fit. Manufacturers like ACL Drayton issue a conversion chart showing how their connections match to others.

If you are electrically adept and can folllow the wiring diagram, you could replicate the connections on a strip of choc-block or something and see if the CH and the HW work when you have connected the appropriate wires. If all the other components work correctly then it must be the programmer at fault. With your problem history I would have expected that. Unless you think you have dislodged a connection or made some other mistake.

 

[electronicsuk]

I'd suspect the programmer rather than a fault in the fixed wiring, but that's no more than an opinion.