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Rad heat only when Hot water is off - even then rads badly

Discussion in 'Plumbing and Central Heating' started by stevesnas, 29 Jan 2015.

  1. stevesnas

    stevesnas

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    Hi All

    I have what I believe is a open circuit heating system.

    Live in a three storey house with 2 rads on ground, boiler and 4 rads on first floor, hot water tank and 4 rads plus controls on second floor.

    I'm not 100% sure but bathroom rad could be on the primary pipe from boiler to pump.

    Boiler seems good as creates lovely hot water.

    Pump is a grundfos installed upside down on setting 3.

    Mechanical valve I think its a Honeywell 3 port valve.

    Issue I'm getting is when hot water and heating on together I don't get any water pushed round the rad system.

    When hot water is off I do but its not great second floor rads get super hot (valves on those rads only a crack open) - rads on first floor get warm - rads on ground floor get nothing.

    I have also noticed attic seems to have lots of moisture (so don't know if getting pumping over - will check tonight as well as try to draw a diagram of pipework )

    Had a power flush on the system about 2 years ago.

    Any thoughts on if its the pump or the 3 port valve, or if I have a blockage somewhere else?

    Every plumber I've ever called seems to only want to suggest another power flush.
     
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  3. ColinEvans

    ColinEvans

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    Hi
    What happens when the hot water is off and the heating is on? Do all the rads work ok then?
    Regards
    Colin
     
  4. stevesnas

    stevesnas

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    When hot water is off I do get some heat to rads but its poor circulation.

    Second floor rads will get super hot , so I've turned the lock valves down on those to just a crack

    First floor gets mild at best.

    Ground floor is non existent - stone cold - I don't even feel any heat on the down pipes to the rads
     
  5. ColinEvans

    ColinEvans

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    Sorry, just re-read your post, I missed the bit about the hot water being off.
    I'm not a heating engineer, hopefully one will reply to your post but it sounds to me more like a pump issue. I had this once one when my pump failed in an old house - the top of the house rads were still warm due to the hot water rising. Hope you get it sorted!
    Colin
     
  6. stevesnas

    stevesnas

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    So here's a diagram of my mangled ch pipes

    Why is there a t off after pump before mechanical port

    Why does that connect to the out flow of the water tank heat pipe

    Why does my inflow to water heater go in at the bottom

    Why 2 pipes going down towards boiler

    What are those weird stand up pipes that go no where for?

    ( the guy that owned this house before me was such a bodger)
     
  7. stevesnas

    stevesnas

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  8. Madrab

    Madrab

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    That looks like an auto bypass (does it have numbers/pressure settings on the top of the black knob?) feeding into the Boiler Return. Do all your rads have TRV's?

    The smaller 2nd pipe could be the return from the upstairs rads but would expect to see 22mm there unless there's a rad close by.

    The 2 'standy up pipes' are manual air vents
     
  9. stevesnas

    stevesnas

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    Only a few have the 3 regular ones on 2nd floor
    Bath rad on second floor and all other rads have basics lock valves

    Can't see any numbers on the bypass pic attached

    Actually one small rad on first floor has a trv ( we currently have this turned off and lock valve off)
     
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  11. Madrab

    Madrab

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    Ah ok, looks awfully like a honeywell auto bypass with the red head taken off, presumably when it was set.

    Reading your original post that you get CH when the hot water is off/satisfied sounds awful like a W plan setup, which gives HW priority at all times.

    When the rads do get the heat, if most of the rads have manual lockshied/twist valves then it could need properly balanced. What speed setting is the pump on?
    Turn off the 2nd floor rads, do the others start to get hotter?
     
  12. stevesnas

    stevesnas

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    Pump is on setting 3

    And yes when rads are working turning off the second floor rads does seem to make a difference.

    Although I've not tried turning of the bathroom rad yet last time I did that the boiler locked out ( baxi solo 18he)

    So been afraid to mess with that radiator yet
     
  13. stevesnas

    stevesnas

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    OK Doesnt seem like I'm on a W plan as, when heating and water both on this morning - both sides of mechanical switch were getting warm.

    Now beginning to suspect the auto bypass valve.

    According to the specs of my boiler (BAXI solo 18HE) it doesn't require a bypass.

    Could a wrongly installed bypass be directing heat from the radiatos and water tank.

    Given that someone helpful removed my plastic cap of the DU145 can I just screw/wrench the valve shut? Anything I need to be afraid of?
     
  14. Madrab

    Madrab

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    Does the bypass pipework get hot at any time?

    The bypass may be a hangover from an earlier boiler and yes it could be causing problems.

    Turning off a rad really shouldn't lockout the boiler unless it causes it to overheats but that's really what the bypass is for.

    Sounds like the system badly needs balanced but TBH Steve I'd be starting to recommend getting a pro in as it sounds like there's something going on that isn't quite right and may need an engineer to check the components (pump/valve/trv's etc) and boiler pipework, check for restrictions/sludging up, review the system's design and diagnose for you properly.
     
  15. stevesnas

    stevesnas

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    Thanks Rob been a lot of help
     
  16. Madrab

    Madrab

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    Don't wish you to think you are being fobbed off Steve, next one to try would be to try balancing the system, which is pretty straightforward to do - http://www.diydata.com/projects/centralheating/balancing/radiator_balancing.php

    TBH though, you could be wandering your way around the forms for ages, picking your way through every part of your system trying to find the issue. With what seems to be a redundant bypass, mixed rads over 3 floors with and without TRV's to balance, locking out a boiler that seems to have 2 bypasses on a Y plan, by only playing with a rad etc.
    It does seem as if something else isn't quite right. A professional would be able to at least diagnose, if not fix, it for you in 1 or 2 visits
     
  17. D_Hailsham

    D_Hailsham

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    1a. Why is there a t off after pump before mechanical port1

    1b. Why does that connect to the out flow of the water tank heat pipe

    That's an autobypass

    2. Why does my inflow to water heater go in at the bottom.

    No reason why it shouldn't. Some say that, in theory, it is better that way round.

    3. Why 2 pipes going down towards boiler

    Are you sure they both go to the boiler? Where are the returns from the rads connected?

    4. What are those weird stand up pipes that go nowhere for?

    Air vents

    When you say the LS valves are cracked open, how much do you mean - 1/2 turn or what?

    Is there a valve on either of the two pipes connected to the side of the HW cylinder?
     
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