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  1. #1
    Join Date
    Jan 2012
    Location
    South Coast
    Posts
    4,455

    Default Hot (very hot) from the cold tap

    I've not investigated yet, but why / how did I get a continuous flow of mega hot water from all my cold taps today. The pump was running continuously, so not achieving system pressure, and every faucet was blasting red hot water from the cold taps.

    There is a non return valve on the cold feed to the calorifier, but possibly stuck open I suppose.

    I solved it by turning off power to the pump, vented the pressure, then re-started the pump which duly pressurised, cut out as normal and normal temperature returned.

    Bizarre.
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  2. #2
    Join Date
    May 2007
    Posts
    30,390

    Default Re: Hot (very hot) from the cold tap

    Check the over-pressure valve in the calorifier.

  3. #3
    Join Date
    Jan 2012
    Location
    South Coast
    Posts
    4,455

    Default Re: Hot (very hot) from the cold tap

    Quote Originally Posted by lw395 View Post
    Check the over-pressure valve in the calorifier.
    The relief valve sits on the outlet and is set at 3.5Bar with the pump pressure cut out at 3 B. Thats working just fine.
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  4. #4
    Join Date
    Feb 2010
    Location
    Caulkhead
    Posts
    67

    Default Re: Hot (very hot) from the cold tap

    Snap. Same problem this weekend on our Hardy 42. I need to have a look at it next weekend.

    My starting point is to check for low pressure on the accumulator; that would potentially explain hot water imbalance on the mixer taps, however we are also getting warm water coming into our fresh water loo, which is odd as that has a COD feed only.

    I’ll follow this discussion with interest.

  5. #5
    Join Date
    Jan 2012
    Location
    South Coast
    Posts
    4,455

    Default Re: Hot (very hot) from the cold tap

    A brief investigation resolved three issues ...

    1 The 27 year old check valve on the cold water supply was heavily scaled up and thoroughly stuck open.

    2 The newly installed calorifier sits at a very slight angle creating a slight bubble above the high point hot water outlet.

    3 This effect was made worse by the thermo reg valve I fitted having its regulated hot water outlet level with halfway down the tank.

    So the fresh water pump was trying to push water in, but with the immersion on and set to max to get the maximum volume of regulated hot water, and with likely part of the immersion sitting in the 'bubble' I had actually created quite an effective steam engine. So the fully heated hot water was simply pushing back into the cold supply line and out of the taps, achieving a partially higher pressure than the pump could manage.

    All below the relief valve pressure.

    I have now replaced the check valve and remounted the reg valve so the hot water outlet is now the highest point.

    A small bubble remains inside the gently sloping calorifier, and unless it continues to cause trouble there it will stay because remounting the tank at a different angle is another job entirely !
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