Problem with Grant Combi Boiler - no hot water

Discussion in 'Plumbing and Central Heating' started by Charon71, 16 Dec 2019.

  1. Charon71

    Charon71

    Joined:
    16 Dec 2019
    Messages:
    16
    Thanks Received:
    0
    Country:
    United Kingdom
    Morning all,

    I’m having a problem with my boiler I’m hoping you can help with.

    I have a Grant Vortex 21e Combi Boiler (Oil). There was a leak (now sorted) which caused the electrics on the HW pump to burn out. I’ve replaced the pump however there is still no hot water.

    When the hot tap is run the flow light comes on and the burner fires but after about 5 minutes the overheat cut off activates.

    The pipe leading into the Heat Exchanger gets warm, but the exchanger itself is not getting hot. I have removed the heat exchanger and cleaned it out (I live in a hard water area) and I can get a good flow through it so I don’t think it’s blocked. I’ve also cleaned/descaled the TMV.

    I’m now at a loss as to what it could be, prior to replacing the pump (which seems to be working fine) everything was ok – does anyone have any ideas?

    Thanks in advance
     
  2. Sponsored Links
  3. Terrywookfit

    Terrywookfit

    Joined:
    19 Jul 2007
    Messages:
    5,786
    Thanks Received:
    1,096
    Country:
    United Kingdom
    Have you fully vented the store and pump.
    Is the pump running on full speed are pump valves open ?
     
  4. Charon71

    Charon71

    Joined:
    16 Dec 2019
    Messages:
    16
    Thanks Received:
    0
    Country:
    United Kingdom
    Thanks for the reply - the pump is on full speed and the valves are open - could you explain what you mean by venting the store and pump please?
     
  5. Terrywookfit

    Terrywookfit

    Joined:
    19 Jul 2007
    Messages:
    5,786
    Thanks Received:
    1,096
    Country:
    United Kingdom
    Are the caps on auto air vents open. There is a manual vent on flow pipe as well.
     
  6. Charon71

    Charon71

    Joined:
    16 Dec 2019
    Messages:
    16
    Thanks Received:
    0
    Country:
    United Kingdom
    Yes, all open and working. Have bled the manual one on the flow pipe.
     
  7. Terrywookfit

    Terrywookfit

    Joined:
    19 Jul 2007
    Messages:
    5,786
    Thanks Received:
    1,096
    Country:
    United Kingdom
    Are the pump flow demand and burner lights on ?
     
  8. Charon71

    Charon71

    Joined:
    16 Dec 2019
    Messages:
    16
    Thanks Received:
    0
    Country:
    United Kingdom
    Yes, when the tap runs the flow light comes on and the burner fires
     
  9. Terrywookfit

    Terrywookfit

    Joined:
    19 Jul 2007
    Messages:
    5,786
    Thanks Received:
    1,096
    Country:
    United Kingdom
    How about the DHW pump light and burner light ?
     
  10. Sponsored Links
  11. Charon71

    Charon71

    Joined:
    16 Dec 2019
    Messages:
    16
    Thanks Received:
    0
    Country:
    United Kingdom
    Yes, all the lights are behaving as they should be. It just runs for five minutes without the heat exchanger getting even warm before the overheat cut off activates. Was wondering if it might be a thermistor?
     
  12. Terrywookfit

    Terrywookfit

    Joined:
    19 Jul 2007
    Messages:
    5,786
    Thanks Received:
    1,096
    Country:
    United Kingdom
    Have you checked for 240v at pump terminals..
    A faulty store thermistor would give a flashing light.
    Is heating ok.
     
  13. Charon71

    Charon71

    Joined:
    16 Dec 2019
    Messages:
    16
    Thanks Received:
    0
    Country:
    United Kingdom
    Power to the pump is ok, the heating is fine thankfully!
     
  14. Terrywookfit

    Terrywookfit

    Joined:
    19 Jul 2007
    Messages:
    5,786
    Thanks Received:
    1,096
    Country:
    United Kingdom
    If the store is Hot the pump is running but no heat to the PHE then there is an air lock or blockage.

    Is the pump correct way round ???

    No flow if wrong due to NRV
     
  15. Charon71

    Charon71

    Joined:
    16 Dec 2019
    Messages:
    16
    Thanks Received:
    0
    Country:
    United Kingdom
    Pump is the same way around as the old one, happy it's going the right way. If it's a blockage what's the best way of clearing it?

    Thanks for the help!
     
  16. Terrywookfit

    Terrywookfit

    Joined:
    19 Jul 2007
    Messages:
    5,786
    Thanks Received:
    1,096
    Country:
    United Kingdom
    Are you sure that the arrow on the pump BODY....not the head is pointing down. It seems strange the fault started after you swapped the pump.
    Have you loosened the screw on pump head and checked it is rotating and there is no trapped air.
     
  17. Charon71

    Charon71

    Joined:
    16 Dec 2019
    Messages:
    16
    Thanks Received:
    0
    Country:
    United Kingdom
    The head is pointing up, tbh I don't think you could get it to fit upside down just because of the shape of it. Have loosened the screw and got water out, I did check it was rotating before I put the water back on initially, seemed ok?
     
Loading...

Share This Page