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Old boiler woes.... ( Worcester 24cdi)

Discussion in 'Plumbing and Central Heating' started by TG88, 3 Dec 2019.

  1. TG88


    3 Dec 2019
    Thanks Received:
    United Kingdom
    Hey guys,

    I have an old Worcester 24cdi boiler. It's basically an antique, and I'm currently saving to replace it, but for the most part I must say its served us well.

    Sunday morning we woke up to a freezing cold flat, I open the boiler cupboard and its flashing on lockout. I reset it and it launches into action. Fan going, pump going, ignites fine, radiators all getting warm. So I write it off as a random fault. 20 mins later. Boom, lockout.

    So I get out the user manual and look at the fault finding section. It says a slow flashing CH demand light means burner(ignition) lockout, so (according to the manual) either a dodgy gas valve or a dodgy flame sensor. Diagnosing and confirming either of those would mean opening chamber and thats out of my territory, not being gas registered. So we battled through a chilly Sunday and Monday morning I called my guy who does all my gas/CH stuff. Unfortunately, he's fully booked till next week. But, he gives me the number of a plumber/gas friend who's nearby, so I thought I would give him a try and fortunately he could come over and take a look.

    So he comes round, (I assume he knows what he's doing coming from such an excellent engineers recommendation) and I leave him to get on with it. He runs a few tests, turning the radiators on and off, and spinning it up and down. Then tells me I have a dodgy overheat sensor, he'll order one and come back in the morning to fit it.

    So this morning 8am, he turns up puts the new part in. Fires up the boiler, tweaks a few bits and tells me its all done £110 pounds, thanks very much. He leaves the flat.

    10 minutes later I hear the radiators ticking down. Open the cupboard. Guess what!!! Burner lockout. In the cupboard I find, two overheat sensor bags, sachets of heatsink compound and the remainder of two sensors. What the hell!!!!

    So we call him up and tell him it's done it again. He comes back, and messes with the boiler some more. Tells me that the boiler is old and running inefficiently and that the CH temp knob had snapped off of the pcb, and it was stuck in the max position. Causing the boiler to get too hot (cause its old) So he turns it right down with a screwdriver, and tells me its sorted and leaves.

    So now, the boiler cycles for about 2 minutes before it cuts out to cool and then goes through another cycle. However, the flat now doesn't get above 16 degrees. Better than 10, and the hot water is working on demand, but still not ideal.

    What could this be? Surely if it was overheating it would display an overheat lockout not a burner lockout? Im a bit reluctant to call out anyone else now. Am I right to be? Manual says burner lockout points to a gas valve, flame sensor or control board fault. Suggesting that if the lockout doesn't arrive at the start of demand, then its more likely a valve or board fault. Plus DHW works fine so unlikely to be the valve. Could it be the board? Any ideas? Do i just need to call British gas or one of the big guys?

    If I turn CH off via thermostat. Then the boiler runs great on DHW only. No lockouts. All radiators heat up so no blockages. Pump is definitely going as is the fan. No leaking, weird noises etc.

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  3. Chris_W


    26 Sep 2019
    Thanks Received:
    United Kingdom
    It looks like there’s a couple of other things to look at, have you asked your normal engineer again?
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    DIYnot Local

    3 Sep 2019
    United Kingdom

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