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Advice needed: Worcester 30si - no hot water

Discussion in 'Plumbing and Central Heating' started by GasmanCam, 27 Apr 2018.

  1. GasmanCam

    GasmanCam

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    Location:
    Camberley
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    Hi, I'd be really grateful if I could get some of your opinions on an intermittent fault that occurring on a customers boiler. (Greenstar 30si mk 3). I have spoken to Worcester about this, but seems like everyone's scratching their heads with it a bit, and I'm not really a fan of just guessing and hoping for the best.

    Thanks in advance!

    Visit 1:
    Customer reports no hot water, but the heating is fine. I visibley can see diverter valve moving to all 3 positions, When power is switched off and then on at fused spur. When tap is opened nothing happens, it's completely static, and no error codes. I confirmed with Worcester that the flow turbine was working. And also dhw thermistor was giving a reading within range. It was recommended the the pcb had failed and should be replaced. Also I noted that the flow rate was crap from tap, about 5 litres per min.

    Visit 2:
    Returned and fitted new circuit board, new board was an updated type without the big transformer on the back. Power back on, all was working perfectly. Heating and hot water both operational. I thought job done.

    Visit 3:
    2 weeks later have to reattend, due to intermittent hot water. Apparently hot water worked fine for a couple of days and then after that not. Customer states sometimes it will run for a few mins then go cold, other times boiler just does nothing (same as initial issue). He also stated sometimes it was very hot. When I test on site, hot water was working as it was supposed to, operating on demand and at the correct temperature.

    Visit 4:
    I reattend and Initial test shows boiler still static when tap opened. Customer also stated that they day before he'd switched it off at the spur due to the boiler vibrating lots when trying to run the hot water. I fit a new flow turbine, flow adaptor, and flow regulator. Also cleaned the inlet filter. Was flow was not really improved to be honest, so pressume there must either be a restriction in the plate to plate, or maybe in the manifold. Test hot water and still boiler does nothing. when I'd re instate power to the boiler the diverter valve would go from mid position to lower and then back to mid. Every 10/15 times of power being resumed the diverter valve would move to the high position and the HW pre heat would start. However once the preheat was over, and a tap opened the boiler would again be static. I removed the diverter valve and it looked to all be in good clean condition. Tried operations with the motor out of site to. See if that made a difference. I again spoke to Worcester, confirmed again the the flow sensor was picking up the demand. Also carried out resistance tests on the diverter valve motor, checked the thermistors which were correct. Worcester said they think it's again a faulty pcb and that I should fit a new one.

    So basically I'm going to go back again with a new pcb, but there's definitely a part of me that thinks it could be something else, like maybe the diverter valve motor?

    It might be worth noting that on this visit I found that the shower thermostatic mixer has a slight issue with the check valves, as when I isolated the cold I let at the boiler and opened taps to drain, I could hear water passing through the mixer and constantly flowing (not much) through the tap. I wouldn't have thought this would be contributing to the boiler issue though?

    Struggling a bit with this one, so any suggestions / thoughts would be greatLy appreciated, thanks.
     
  2. Nozzle

    Nozzle

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    This is an interesting read for someone like me, in the market for a new boiler. Sorry I can't help with the problem though

    Nozzle
     
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  4. mcmoby69

    mcmoby69

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    There's your problem. Cold is back feeding down the hot pipe to water ever tap is open. You're not getting full flow through the boiler.
     
  5. GasmanCam

    GasmanCam

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    Location:
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    Thanks for your reply, I will isolate it and see what happens. I was thinking that might have been a red herring, due to the flow turbine still registering a flow when the hot taps opened.
     
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