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Back Boiler Loud Gurgling Noises

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  • 14-10-2013 10:16am
    #1
    Hotwater
    Registered Users Posts: 4 ✭


    Hi all.
    I have an oil fired central heating system that also has a fireplace with a back boiler plumbed into it. The system has a dual coil copper cylinder with the oil side heating one coil and the back boiler the other. There is a pipe stat on the back boiler supply to the copper cylinder which starts a circulating pump which then transfers heat to the central heating radiators when the desired temperature is achieved. There are also three non-return valves in the system. A standard enough system in other words.

    My problem is this - the heating has been running with no apparent problems for years but recently when the back boiler circulating pump cuts in I can hear loud gurgling noises from the copper cylinder. It sounds like there is an amount of air in the system and that the water is just trickling through the back boiler coil on the tank. When the thermo siphon is operating everything is quiet and heat is being transfered from the back boiler to the copper cylinder. When the oilfired heating circ pump is operating everything is quiet aswell.

    The system doesn’t appear to be losing any water as I have tied up the ball cock in the expansion tank and the level has not dropped over a week, even though one of the radiators does need to be bled frequently.
    I have had the back boiler circ pump running for long periods with no fire lit to try and work any air in the system out of it with no success.
    I have had the thermo siphon circuit flushed and have been told that there is a no problem with the flow through it.
    I also get plenty of domestic hot water when the fire is lit.
    The radiators do get warm throughout the house when the back boiler circ pump is dumping the heat to them, but it is when the back boiler circ pump is running that I get this loud gurgling sound.

    If any of you experts out there have any light to shed on this it would be much appreciated.
    Tagged:


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    #2
    rightjob!
    Registered Users Posts: 478 ✭✭rightjob!


    try bleeding the pump?
    sounds like there is air in it alright,why does one radiator have to be bleed a lot,leak under the floor?does your expansion ever pitch?


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    #3
    Hotwater
    Registered Users Posts: 4 ✭Hotwater


    Thanks rightjob ......

    Have bled the pump but still have the problem.
    I tied up the ballcock in the expansion tank for over a week to check for a leak but didn't lose any water.
    No the system isn't pitching


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    #4
    rightjob!
    Registered Users Posts: 478 ✭✭rightjob!


    has to be air trapped in it,have you tried putting a hose onto the safety valve and letting it run out?


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    #5
    Hotwater
    Registered Users Posts: 4 ✭Hotwater


    rightjob! wrote: »
    have you tried putting a hose onto the expansion valve and letting it run out?

    where is the expansion valve?


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    #6
    rightjob!
    Registered Users Posts: 478 ✭✭rightjob!


    ment to type safety valve,is there not a safety valve fitted near the back boiler?
    google safety valve


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    #7
    Hotwater
    Registered Users Posts: 4 ✭Hotwater


    The safety valve for the back boiler is in the attic and because of this I am assuming that the vent/expansion pipe should do the same job letting air out of the system but I will try what you suggest. There is one out at the oil fired boiler and I fitted a service valve out there aswell to help bleed the system.
    There doesn't seem to be a problem with air in the back boiler thermo syphon circuit that appears to operate correctly it is only when the back boiler circ pump cuts in to circ the rads that there is the problem. I have tried bleeding the air out at different fittings in the hot press but with no success.


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