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  • FIRST POST
    • Kiran
    • By Kiran 16th Jan 20, 3:59 PM
    • 1,326Posts
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    Kiran
    Automatic Bypass Valve
    • #1
    • 16th Jan 20, 3:59 PM
    Automatic Bypass Valve 16th Jan 20 at 3:59 PM
    I've just fitted Honeywell Evohome system in my house. All works fine however I'm getting a fairly loud rumbling in the pipes/rad from the lounge radiators. I've done a bit of reading up on this and it appears to suggest that I need an automatic bypass valve. My question is, is there a minimum distance from the boiler that you need to be before you join the flow and return loops? I presume that it needs to be before the first radiator but if it's too close to the boiler does it present an issue? I've got a floor standing oil boiler in my utility room and the pipes disappear under the floor within the height of the boiler (approximately 900mm). Also, is there a minimum length the bypass loop needs to be?


    Thanks in advance
    Some people don't exaggerate........... They just remember big!
Page 1
    • Kiran
    • By Kiran 17th Jan 20, 8:12 AM
    • 1,326 Posts
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    Kiran
    • #2
    • 17th Jan 20, 8:12 AM
    • #2
    • 17th Jan 20, 8:12 AM
    Shameless bump, there used to be some really good plumbing and heating experts on this forum and I'm hoping one of them can help
    Some people don't exaggerate........... They just remember big!
    • jefaz07
    • By jefaz07 17th Jan 20, 8:50 AM
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    jefaz07
    • #3
    • 17th Jan 20, 8:50 AM
    • #3
    • 17th Jan 20, 8:50 AM
    What type of system do you have?
    • Kiran
    • By Kiran 17th Jan 20, 9:31 AM
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    Kiran
    • #4
    • 17th Jan 20, 9:31 AM
    • #4
    • 17th Jan 20, 9:31 AM
    It's a Worcester Heatslave 26/32 combination oil boiler.


    It's feeding 14 rooms including bathroom, airing cupboard, WC etc. All the radiators are under control of TRV's. Of those TRV's 11 are Evohome TRVs, the remaining are standard manual TRV's.


    I've created a temporary bypass by fully opening the TRV's on the bathroom, WC and airing cupboard which has certainly improved the issue. When the lounge shuts down now you get a short rumble/vibration which leads me to think I was on the right track with a bypass being required?


    Thanks
    Some people don't exaggerate........... They just remember big!
    • Kiran
    • By Kiran 20th Jan 20, 6:11 AM
    • 1,326 Posts
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    Kiran
    • #5
    • 20th Jan 20, 6:11 AM
    • #5
    • 20th Jan 20, 6:11 AM
    One final shameless bump and I'll let the thread die. Any advice gratefully received. It's frustrating as it's making what would be an excellent system quite irritating.
    Some people don't exaggerate........... They just remember big!
    • FreeBear
    • By FreeBear 20th Jan 20, 11:46 AM
    • 3,548 Posts
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    FreeBear
    • #6
    • 20th Jan 20, 11:46 AM
    • #6
    • 20th Jan 20, 11:46 AM
    All the radiators are under control of TRV's.
    Originally posted by Kiran

    At least one radiator should not be fitted with a TRV. This will be the radiator in the same space as the thermostat (normally, the hallway). You do have a thermostat don't you ?
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    • Rodders53
    • By Rodders53 20th Jan 20, 3:20 PM
    • 793 Posts
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    Rodders53
    • #7
    • 20th Jan 20, 3:20 PM
    • #7
    • 20th Jan 20, 3:20 PM
    Bypass loops are only required:
    1 If there's a frost protection thermosat... as no 'call for heating' is coming from any other radiators etc.,. and the valves will be closed to any water flow.

    2 If there's a need for the boiler to have the pump 'run on' to dissipate heat in the heat exchanger and the other heating controls shut down the pipework (via 2 port valves).

    3 If all radiators have TRVs and there is only a CH timeswitch control (but it is usual to use a bathroom radiator/towel rail as the 'bypass' loop in that situation).

    Read the boiler installation manual for the makers' advice ref bypass loops.

    You appear to have a different issue along the lines of a water hammer effect when the (motorised) Honeywell TRV on the lounge closes.

    It's not unknown for TRVs to make noises when they open/close due to the water turbulance created. Try altering the flow rate via the lockshield valve on that radiator?
    Some older TRVs are unidirectional so make sure the flow direction is correct as well?
    • Kiran
    • By Kiran 20th Jan 20, 9:02 PM
    • 1,326 Posts
    • 617 Thanks
    Kiran
    • #8
    • 20th Jan 20, 9:02 PM
    • #8
    • 20th Jan 20, 9:02 PM
    At least one radiator should not be fitted with a TRV. This will be the radiator in the same space as the thermostat (normally, the hallway). You do have a thermostat don't you ?
    Originally posted by FreeBear


    Thanks, I've double checked and I do have 2 un controlled rads with no TRVs. One bathroom and one airing cupboard. With the evohome you don't have a single thermostat, its built into the TRVs so you can zone your house to different temps
    Some people don't exaggerate........... They just remember big!
    • Kiran
    • By Kiran 20th Jan 20, 9:07 PM
    • 1,326 Posts
    • 617 Thanks
    Kiran
    • #9
    • 20th Jan 20, 9:07 PM
    • #9
    • 20th Jan 20, 9:07 PM
    Bypass loops are only required:
    1 If there's a frost protection thermosat... as no 'call for heating' is coming from any other radiators etc.,. and the valves will be closed to any water flow.

    2 If there's a need for the boiler to have the pump 'run on' to dissipate heat in the heat exchanger and the other heating controls shut down the pipework (via 2 port valves).

    3 If all radiators have TRVs and there is only a CH timeswitch control (but it is usual to use a bathroom radiator/towel rail as the 'bypass' loop in that situation).

    Read the boiler installation manual for the makers' advice ref bypass loops.

    You appear to have a different issue along the lines of a water hammer effect when the (motorised) Honeywell TRV on the lounge closes.

    It's not unknown for TRVs to make noises when they open/close due to the water turbulance created. Try altering the flow rate via the lockshield valve on that radiator?
    Some older TRVs are unidirectional so make sure the flow direction is correct as well?
    Originally posted by Rodders53


    Thanks, the trv and lock shield are backwards on a couple of the rads, as I don't know the age of the ones that were there I'll try changing them. The system could probably do with a flush through too. I'll give it a try and see how it goes.
    Some people don't exaggerate........... They just remember big!
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