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Alpha 280E boiler problems

Discussion in 'Plumbing and Central Heating' started by logik, 12 Dec 2008.

  1. logik

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    I have an Alpha 280E boiler. For the last year (since I moved in) it has been a little temperamental, the DHW would cycle hot-cold every 10 seconds every so often. The heating was always fine.

    Over the last week it has got much worse. The boiler fires and the pump works. Radiators only get lukewarm and therefore the house is very cold! DHW either cycles constantly (with more cold than hot) or doesn't warm up. When running the DHW, the boiler fires at the first demand but then extinguishes after a few seconds.

    A local plumber couldn't find any exact problem and suggested it might be the circuit board. He made this assumption because the pump was running and the CH diverter pin was fully out, even though there was no demand (he tested the thermostat wiring which was fine). I had turned the boiler off & on at the wall though, so it is possible the pump was trying to run for 5 minutes, which it is supposed to do once every 24 hours. Once again, the boiler was lighting and then extinguishing during this period. I played stupid and only asked questions about "that valve thing there" when he explained how it worked.

    When I turned on a tap, the pin from the DHW diverter came out as expected. However, the pin from the CH diverter also stayed out. When the tap went off, both pins went in, microswitches turned off and the boiler stopped lighting/extinguishing as it had been. This makes me wonder if the CH diaphragm (or even the diverter?) is faulty, from reading other posts in this forum.

    I'm sure the whole thing (heat exchangers, filters on cold inlet & heating return) needs a good clean. I could do this, but obviously I don't want to touch anything related to gas.

    So does anybody have any clues or troubleshooting I could do to determine the problem? I have phoned Alpha who simply redirect the call to Homeserve (who wont help as the boiler is >2 years old). I'll try and get through to their customer service but I'm reluctant to call them out for a hideous fee unless it's clear the boiler needs a lot of work.
     
  2. gas4you

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    Try changing the CH thermistor ;)
     
  3. logik

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    OK, I can do that, thanks. However shouldn't the CH side of the diverter close when the hot water side opens? The pin definitely stays up (just tested it). I guess this could also cause the hot/cold problem with the water?

    I'll have a look through the service manual tomorrow and see if I can find the part number. It's actually a 240E, not a 280, so I'll search the forums again tonight.

    Thanks again.
     

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