Pipes clanging when DHW calls or heat

Discussion in 'Plumbing and Central Heating' started by spike47, 18 Nov 2021.

  1. spike47

    spike47

    Joined:
    18 Jun 2011
    Messages:
    74
    Thanks Received:
    0
    Location:
    Yorkshire
    Country:
    United Kingdom
    Hi

    Problem : Pipes clanging when DHW calls for heat

    Scenario, vented system CH system, clanging of pipes in a morning ( only morning ) when system starts up, have bled the system, set pump to II , no noise but downstairs rads not getting hot, pump back to III , turned DHW thermo down to "O" just before bed time, morning boiler fire up for CH only , no noise.


    So I take it that the noise is caused by the DHW calling for heat first thing on a morning, during the day/evening no noise, now there is no programmer for this system, have made a drawing from the junction box wiring under first floor !.


    So do you think it is doing that first thing on a morning with cold pipes, when they warm up a bit the problem seems to be cured, just a guess.

    I think I need really to change the priority to CH, and then I think the problem will go away !.
    or could I put a timer just to the DHW cylinder !

    ps: not my system, Mams .
    Spike
     

    Attached Files:

  2. Sponsored Links
  3. DP

    DP

    Joined:
    10 Dec 2003
    Messages:
    15,191
    Thanks Received:
    3,376
    Location:
    Glasgow
    Country:
    United Kingdom
    Is the three port valve Honeywell?
     
    • Thanks Thanks x 1
  4. spike47

    spike47

    Joined:
    18 Jun 2011
    Messages:
    74
    Thanks Received:
    0
    Location:
    Yorkshire
    Country:
    United Kingdom
    Siemens DVA3.


    edit: Sorry not sure what make the valve is, just a plain 3 port valve , the Actuator is a Siemens mid way !.

    Spike
     

    Attached Files:

    Last edited: 24 Nov 2021
  5. MeldrewsMate

    MeldrewsMate

    Joined:
    27 Jan 2010
    Messages:
    1,125
    Thanks Received:
    282
    Location:
    Buckinghamshire, Darn Sarf
    Country:
    United Kingdom
    The basic circuit looks adequate; the links are there to take the place of the missing programmer.

    Have you considered this clanging to be from expanding pipework close to ceiling joists?
    Have you inspected and cleaned the pump impellor?
    Is there a restrictor valve, usually a 22mm gate valve, on the hot water cylinder primary return?
    Is the heating system single pipe?
     
    • Thanks Thanks x 1
  6. spike47

    spike47

    Joined:
    18 Jun 2011
    Messages:
    74
    Thanks Received:
    0
    Location:
    Yorkshire
    Country:
    United Kingdom
    Hi
    Thanks for your replies.

    1: I don't think it will be from pipes expanding, it happens on a morning as soon has it fires up.

    2: Pump is new ( 6 months old).

    3: No gate valve on DHW Tank.

    4: Yes, 22/15

    Spike
     
  7. spike47

    spike47

    Joined:
    18 Jun 2011
    Messages:
    74
    Thanks Received:
    0
    Location:
    Yorkshire
    Country:
    United Kingdom
    Could I change over from DHW priority to CH priority, if so how can I do that ?.

    if the CH comes on first with the cylinder stat turned down, then after a hour, you turn the cylinder stat back up, there is less noise when the DHW kicks in !

    Spike
     
  8. MeldrewsMate

    MeldrewsMate

    Joined:
    27 Jan 2010
    Messages:
    1,125
    Thanks Received:
    282
    Location:
    Buckinghamshire, Darn Sarf
    Country:
    United Kingdom
    As you wish.
    1. First thing is exactly the time when pipe expansion noise will be greatest
    2. A new pump can get clogged with sludge minutes after it was fitted; and have you asked yourself why the old pump was changed? Did you know that a new pump will increase the system velocity, and enable it to keep sludge in solution better....just sayin':whistle:
    3. gate valve would enable better system balancing, though less so on a single pipe system.
    4. Assuming (because you haven't said) a 10 to 15 rad single pipe system, a pump speed of No.2 should be adequate unless it's output is reduced.
     
    • Thanks Thanks x 1
  9. DP

    DP

    Joined:
    10 Dec 2003
    Messages:
    15,191
    Thanks Received:
    3,376
    Location:
    Glasgow
    Country:
    United Kingdom
    Unable to distinguish if the valve has a ball type mechanism similar to Honeywell or shutter like in a Sunvic
    It is not uncommon for Honeywell to behave like this; the valve stays in the last operated position. When pump runs, eg valve is released from heating to hot water port, that is when the noise occurs.

    Check it out. Put the heating to off on the programmer and run the system like you would during summer ie heating off. Post if the noise still there.

    Have seen that happen.
     
    • Thanks Thanks x 1
  10. Sponsored Links
  11. spike47

    spike47

    Joined:
    18 Jun 2011
    Messages:
    74
    Thanks Received:
    0
    Location:
    Yorkshire
    Country:
    United Kingdom

    It seems the knocking is when the HW comes on, turned HW thermo down and CH started on the morning and no knocking !.

    Spike
     
  12. DP

    DP

    Joined:
    10 Dec 2003
    Messages:
    15,191
    Thanks Received:
    3,376
    Location:
    Glasgow
    Country:
    United Kingdom
    The valve is spring return. In its unpowered state, the HW port is open. For CH and HW demand, valve motors to mid position. With HW satisfied, CH still calling, motor drives the valve further to close the HW port. Now CH is satisfied. The valve is under tension but is locked in present state under power

    Now you decide to have a bath and are running a hot tap. If the HW zone is still active, HW ports needs unblocking. The valve releases and restoration is by the spring as well as the pumped water- it slams close. Will not happen for CH
     
    • Thanks Thanks x 1
  13. spike47

    spike47

    Joined:
    18 Jun 2011
    Messages:
    74
    Thanks Received:
    0
    Location:
    Yorkshire
    Country:
    United Kingdom
    It happens ( The clanging ) first thing on a morning, when the boiler fires up for Hot water !
     
  14. Harry Bloomfield

    Harry Bloomfield

    Joined:
    30 Dec 2018
    Messages:
    9,715
    Thanks Received:
    1,314
    Country:
    United Kingdom
    The lock power is reduced power - the motor is powered via a diode, which provides half-wave, which effectively stalls the motor.
     
    • Thanks Thanks x 1
  15. DP

    DP

    Joined:
    10 Dec 2003
    Messages:
    15,191
    Thanks Received:
    3,376
    Location:
    Glasgow
    Country:
    United Kingdom
    Perhaps read what I wrote above again :sleep::sleep::sleep::sleep:

    I KNOW the boiler knocks when you put the hot water on
     
  16. DP

    DP

    Joined:
    10 Dec 2003
    Messages:
    15,191
    Thanks Received:
    3,376
    Location:
    Glasgow
    Country:
    United Kingdom
    ok Sherlock:ROFLMAO::ROFLMAO::ROFLMAO:
     
  17. spike47

    spike47

    Joined:
    18 Jun 2011
    Messages:
    74
    Thanks Received:
    0
    Location:
    Yorkshire
    Country:
    United Kingdom
    I don’t put the HW on, when the boiler fires up first thing in a morning the valve is already open for HW !
     
Loading...

Share This Page