Apollo 30B Pump fails to start

Discussion in 'Plumbers' Talk' started by Boots1066, Jul 31, 2021.

  1. Boots1066

    Boots1066 New Member

    Hi Can anyone please give advise on how to solve a pump problem I have, When boiler is set to Hot Water/ Central Heating mode, Boiler and pump run fine, but when I toggle switch to Hot Water only boiler runs and cycles on cut out thermostats because the pump fails to start. all help welcome. Thanks Alan
     
  2. pppmacca43

    pppmacca43 Super Member

    I’d hazard a guess at a pcb fault but you will need a gas engineer to come and investigate and go through the fault finding process.
     
  3. Bob Rathbone

    Bob Rathbone Screwfix Select

    If it is a system boiler I would check that the coil in the hot tank was free of air, bleed it by the bleed screw, if that fails it may be the 3 port valve. If it's a combi boiler, it could be a blocked secondary heat exchanger.
     
  4. pppmacca43

    pppmacca43 Super Member

    I assume it all works and heats up hot water fine when it’s on both heating and hot water so that’d likely rule out the above suggestions
    He said the pump doesn’t come on at all when only in hot water mode but boiler fires up, if that is the case that’s what’s causing the overheat lockout.
     
  5. Mike83

    Mike83 Screwfix Select

  6. Mike83

    Mike83 Screwfix Select

  7. Boots1066

    Boots1066 New Member

    Hi all, thanks to everyone with there suggestions, the boiler was put in when the house was built in 1982, so has no PCB and is not a condensing boiler, all controls are external to the boiler apart from all the safeties. have changed the 3 way head as the spindle rotated freely. have ordered a tank thermostat but may be just clinging to straws. Thanks again for your advise. Alan
     
    pppmacca43 likes this.
  8. pppmacca43

    pppmacca43 Super Member

    Wow, 40 years old it’s done well!! You might even struggle to get parts for it.
     
  9. Boots1066

    Boots1066 New Member

    Hi, As regards to spares, the builder built a small estate, and over the last 20 years or so, as people on the estate have upgraded and discarded there old boilers i asked them if i could take parts, so have used a good number of preowned spare parts and still have a number to last a few years to come. Alan
     
  10. pppmacca43

    pppmacca43 Super Member

    That’s a good idea
     
  11. dcox

    dcox Screwfix Select

    Have you considered that the hot water circuit could be gravity circulation only. There are usually two pairs of flow & returns (or at least two flows and one combined return) if this is the case.

    *edit: just reread the thread and saw you mention the three way valve, so my idea can’t be right.
     
  12. Boots1066

    Boots1066 New Member

    The 3 way valve is moves to its correct position in both modes before boiler and pump are powered on, cannot figure out why in one mode i.e. Hot water/ central heating the boiler fires up and in turn starts the pump, and when the tank stat calls for heat in Hot Water mode, the boiler starts as normal but you can hear when the water that is sitting in the heat exchanger quickly starts to thermal hammering followed by the boiler cycles on the high temperature stats because the pump fails to run.
     
  13. Teki

    Teki Screwfix Select

    Have you checked that the microswitch in the 3-way valve is closing in hot water only mode?
     
    pppmacca43 likes this.
  14. heatyman

    heatyman Well-Known Member

    Low water content boiler will not be gravity hot water. The pump will be switched by the same switched feed as the boiler. Check all your connections, and the toggle switch operation and also check that the3 way valve is actually closing to hot water.
     
  15. Mike83

    Mike83 Screwfix Select

    Is the pumps power supply fed from the boiler as it should be?
    The pump live should come from the boiler to ensure the pump overrun works.
    Does the pump have a permanent live and switched live or just switched live?
     
  16. Bob Rathbone

    Bob Rathbone Screwfix Select

    He has not stated that the hot water gets hot, it may not be working due to an air lock in the top of the cylinder coil. When DHW only is selected the air lock may prevent water circulation and the over temp stat will operate as described. We do not know all of the facts yet.
     
  17. pppmacca43

    pppmacca43 Super Member

    Fair point :)

    Why would the pump not start though? He definitely said that it fails to start
     
  18. Boots1066

    Boots1066 New Member

    Hi pppmacca43, Thanks for your response, sorry I could not respond till now, before fitting the new 3 way valve head I checked to continuity of both relays for continuity, when insitu the valve made contact with relays and output from the lower relay on orange line voltage output was registered.
     
  19. pppmacca43

    pppmacca43 Super Member

    I think u mean Teki, who u are responding to:)
     
  20. Boots1066

    Boots1066 New Member

    Hi Bob, Thanks for input, the boiler in HW/CH mode heated the water as normal, the pump and boiler run as normal, the wall thermostat set at 5 degrees to prevent central heating kicking in. the hot water tank will heat up until tank temperature reaches its set point which is set to 60 degrees.
     
    pppmacca43 likes this.

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