Alpha CB28 combi boiler

Discussion in 'Plumbers' Talk' started by snipper1, Mar 16, 2006.

  1. snipper1

    snipper1 New Member


    Had this boiler fitted about 3 years ago without any problems.. until this week..
    1.Runs 7 rads and conservatory underfloor heating without any problems BUT now when the hot taps are turned on the boiler doesn't switch so therefor no hot water.
    2.You have to "turn on" "turn off" several times and eventually it switches. The water is red hot at first then stabilizers.
    3.Always had a water softner in place so shouldn't be lime scale damage.

  2. DB

    DB New Member

    I bet its the domestic hot water flow switch diaphram. This operates a microswitch when it senses that the DHW is flowing. These daiphrams often split and then the switch dosent get operated. They can be replaced easily.
  3. The-Gas-Man

    The-Gas-Man New Member

    DB is correct ( most likely ) The Diaphragm is classed as a consumable part which is designed to 'wear out' so that other more expensive parts do not. You require a diaphragm service kit for your CB28 and the part number is:
    " 3.013389 DHW flow valve diaphragm "

    You will require an experienced gas engineer to carry out the repair. This would probably cost between £75 and £125 depending on your location.
  4. snipper1

    snipper1 New Member

    Thanks for you reply, located the DHW and cleaned around it, flicked it a few times..... seems to have free'd up the paddle, may have temporarily cured it... only time will tell.

  5. PhilGPS

    PhilGPS New Member

    the flow switch is also a known fault on the alpha cb28 and shows the same faults as a diaphram.
  6. snipper1

    snipper1 New Member

    Had the diaphram changed and all was ok for a few weeks..... then a stone cold bath!! the glitch is back.
    "can only be the switch cant it" ??????

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