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Constant air in Primary boiler circuit

Discussion in 'Plumbing and Central Heating' started by Marty1966, 21 Apr 2020.

  1. Marty1966

    Marty1966

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    Having had the hot water cylinder recently relocated to the loft the following is now occurring -
    There's a continuous gurgling and sloshing of water in the flow and return pipes and pump when the boiler fires for the HW circuit so clearly its sucking in through the expansion pipe i assume???

    Ive connected a hose to the drain point on pipework on one side of the pump (situated directly on top of the boiler) and its small but continuous air escaping amidst the water being discharged. (F&E tank is topping up ok)
    The auto bleed valve on the return coil also releases air regularly albeit small amounts. (Should the bleed valve not be on the flow circuit)?
    Ive bled the pump and it too emits a regular vent of air bubbles whilst running also.
    Im thinking - should the pump be closer to the HW cylinder would that help? Others have noted the pump has been fitted so as to pump on the return rather than the flow - is that a guaranteed cause or liable to exacerbate the issue?
    If the Feed is moved to where the expansion Pipe is would that equalise the pressure and stop the suction of air into the system ? The feed and expansion ideally are meant to be within 150mm of each other?
    Also understand the 'minimum' distance from the bottom of the F&E tank to the point where the expansion pipe joins the heating circuit needs to me 4ft?
    Would changing the feed pipe from 15mm to 22mm help at all?
    Failing all of the above options would an expansion vessel solve the problem assuming the boiler is compatible ?
    A lot of questions I know ...
    Its still producing HW but the noise cant be normal and the risk of damage to the pump cant be good ....



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  2. oldbuffer

    oldbuffer

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    With the hot water cylinder in the loft, is the primary coil higher than the F&E tank?
     
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  4. Marty1966

    Marty1966

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    Hi, the top of the coil is approx 3-4 feet below the bottom of the F&E tank, I can measure it to be certain tho. Thanks
     
  5. Marty1966

    Marty1966

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    its 3 feet exactly
     
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