Problem With Promax Combi HE Plus Boiler

Discussion in 'Plumbers' Talk' started by joes, Dec 24, 2022.

  1. joes

    joes New Member

    Having a problem with my central heating system which will not heat radiators sufficiently. Everything worked OK for years but heating has not been on for about a year. I can get individual rads fairly warm when all others have been turned off. Rads have been taken outside and flushed, refitted and 1 litre of Adey MC5 Rapid Flush Cleaner added to the system. Left to cycle for 7 days. Drained system and refilled with water but no difference in performance.

    With boiler turned up to maximum, about 80 on the dial, it fires up OK, with fan coming on for about 6 seconds before burner lights up. Burner keeps lit until temperature reaches 80/85 for about 1 minute and shuts off without radiators getting to temperature. This on/off cycle continues for a period of about half an hour before I can get 1 of the main radiators to get warm.

    There are 2 small rads close to the boiler area which heat up fine and quick. One is in the kitchen area and the other in a small toilet/shower room. Being next to the boiler the pipes to them are short runs dropping down from the ceiling. Of course, knowing there is no problem with these, they are turned down to try and get heat to rads in other parts of the house

    What seems strange is that the return in the boiler stays very hot. I think that this used to get quite cool before the boiler fired up to send more heat as required for the radiators.
     
  2. Mike83

    Mike83 Screwfix Select

    What’s the bypass set up in the boiler?
    Does it go around the copper pipe at the back or does it utilise the diverter cartridge?
    If it uses the cartridge and dhw heat exchanger as the bypass then the cartridge could be worn.
    The filter at the return isolation valve may also be partially blocked.
     
  3. MGW

    MGW Screwfix Select

    1) The lock shield valves have been tampered with, and now need resetting.
    2) The by-pass is stuck open.
    3) The pump has failed.
    4) The motorised valve has not opened.
     
    Tricky Dicky likes this.

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