Glow worm 30 cxi problem with Heating Always ON

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Hope someone can help with the following...

I had an issue with No Hot Water and after going to the boiler I noticed the Pressure was going all over the place 0.5, 0.8, 1.2, just cycling through different pressures and the fan was making a whirring noise. I turned everything off and removed the PCB to check for loose or dodgy connections. On replacing the PCB the hot water came back and everything seemed good. However my heating stated to come on, on it's own without being called from the thermostat dad then my Hot Water problem came back.

I decided I must have a problem with my PCB so decided to replace it, as well as the DCW Filter which had deteriorated and the Diverted Valve Motor for no reason apart from I had a new one one.

On replacing all parts, my hot water problem was solved and I was no longer getting the strange pressure issue and hot water is as it was, all good. However I still have the Central Heating Issues.

As soon as I switched the boiler on the central heating came on, almost like I had the voltage free heating control link still bridged.

I tried resetting the boiler (switching off for 5 mins then switching back on) after a number of tries everything seem to be normal again, however 10 mins later the CH fired up again with no call from the thermostat, the only way to switch off was to turn off CH from the boiler switch.

Things I have tried:
  • Switched Off Hot Water completely and just left CH on (Heating still fired up without a call)
  • Removed the Mains voltage heating control plug so no thermostat was connected. (Heating still fired up)
  • During the period when all was quiet and everything seem to work I tried the Main Thermostat and the boiler fired up when called and went off when it was meant to, I also tried bridging the voltage free heating control link and this worked as expected, when bridged the boiler fired up, when removed it went off again.
So basically I'm now in a position where if I want CH I need to turn it on at the boiler rather than being able to use the thermostat.

If anyone has any other ideas on what I may want to check I'd be very grateful to hear your thoughts.

Thanks,

Ben
 
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I would guess the frost protection is kicking in, not sure on your model but most boilers use the main ntc as the frost sensor so if it drifts out of calibration the boiler thinks its colder than it really is and brings heating on.
 
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Hi Picasso,

As far as I can tell the optional frost protection isn't installed in the boiler itself, the wire for this feature going into the mains voltage heating control plug isn't present. Instead I have a British Gas FS1 that is linked to the WR1 wireless system so if this was faulty I guess removing the mains voltage heating control plug which I have already done would have ruled this out.

Regards,

Ben
 
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According to the manual its got frost protection built in... ?
Capture.PNG

do you know the gc number of your boiler?
 
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Oh Ok... Found that bit in the manual after seeing your picture, The manual shows G.C. No. 47-047-24. Should I be testing the Thermistor CH Flow and Thermistor CH Return? In the wiring/parts diagram I can' see anything that specifically refers to the frost protection device.

Thanks for your help with this.

Regards,

Ben
 
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Managed to check them tonight, setting the multi-metre ohms range to 200K I get the following readings: CH Flow Thermistor 12.3 and on the Return Thermistor 9.1 so I think these look ok.
 
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I tested the Thermistors on the boiler itself, the return pipe was warmer than room temperature so I think 9 was reading ok, probably would have been in 11,000 and 13,000 range at room temperature. The link I was testing was on the voltage free heating control plug, this is normally not present and removed, there is no link on the orange plug.

I'm thinking about taking apart the Diverter Valves on the Hydroblocks today see what condition they are in. Would you expect a sticky valve to result in this kind of issue?
 
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As the thermistors are ok double check the connections on the board, its very easy to get the plugs back to front or upside down on the symsi boards.
 
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Connections on the board all look good. I tested the Thermistors again at Room Temp and both read around 11000 ohms. I've removed the diverter valve from the LH Hydroblock and it didn't look too bad so gave them a good clean and made sure everything moved freely, put everything back together and still the problem persists.. Central Heating comes on straight away with no call...!

Could I be looking at a problem with the 230v Controls Interface? Any way of testing this board?

Thanks again for everyone's help..
 
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With flow sensor (Assume this is what you meant by hw turbine) disconnected the heating still come one straight away.
 
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