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Is my differential bypass valve stuck?

Discussion in 'Plumbing and Central Heating' started by John2016, 29 Jan 2019.

  1. John2016

    John2016

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    Hi,

    Our radiators on the bottom floor are not getting hot, I've been having a look on the weekend and came across the bypass valve on my S Plan, three zone (inc hot water) system.

    When the heating system is fully on, the pipes to and from the bypass valve are very hot.

    It would look to me that the valve is stuck open and does not close. I have taken pictures of the valve early morning when the pipes are stone cold.

    What is the best method to loosen the valve and get it working again?

    Thank you.

    file.jpeg file1.jpeg
     
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  3. D_Hailsham

    D_Hailsham

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    Is the valve the correct way round - arrow points from flow to return?
    What number is it set to?
     
  4. John2016

    John2016

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    Hello,

    The flow and return are correct based on the pump.

    There is no number on the valve, does not seems it can be turned.

    Reading online mentions the valve would adjust itself based on flow.


    Thanks
     
  5. ScottishGasMan

    ScottishGasMan

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    you need to take the clear cover off it before you can turn it.

    1st, turn on only the zone thats not been heating, make sure other heat zone and HW are off. then check the zone valve to that zone has actually motored open, if it has, remove the clear cover from BYpass and turn the handle clock wise to close it down and see if any heat pushes to that part of the system.
     
  6. John2016

    John2016

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    Hello,

    I've tried to take over the clear cover, but it does not come off.

    I looked online as we have a Kingspan system and it mentions a automatic bypass valve, so I'm thinking that it adjusts itself?
     
  7. D_Hailsham

    D_Hailsham

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    I have attached the manufacturer's instructions.

    The valve is automatic in the sense that it opens and closes automatically depending on the water pressure. The actual pressure at which it opens will depend on the installation; the valve has to be adjusted so it opens at the correct pressure.
     

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  8. John2016

    John2016

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    Thanks all,

    I will need some sort of mirror to take the reading as its on the other side.

    However, from cold, I will ensure everything is off and the valve is in the closed position. I will then turn on both zones and HW and let the system reach temperature. I will then turn the valve slowly counter-clockwise until the valve begins to open, I can monitor this by the temp. At this stage turn the knob clockwise half a turn to complete the setting process.

    Should I be using the above method, or do I need to read the boiler manual and understand the pump speed (which is set to high, I have microbore) to then work out the right settings.
     
  9. D_Hailsham

    D_Hailsham

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    Make and model of boiler?
     
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  11. John2016

    John2016

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    I have a Potterton SL 15 with Kingspan TT210PT4 with a Grundfos UPS025-60 Pump set on Speed 3.
     
  12. D_Hailsham

    D_Hailsham

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    Can you be a bit more specific as there are several SL 15 boilers. The GC number (on manual or boiler data plate) would help
     
  13. D_Hailsham

    D_Hailsham

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    The pump PN number (on front data plate) would help identify the correct pump curves.

    How old is the system?
     
  14. John2016

    John2016

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    The GC Number 41-591-87
     
  15. John2016

    John2016

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    The system is five years old.

    For the pump I have the following:

    Grundfos
    UPS025-60 130
    P/N: 97781518
    PC: 1239KIN

    Thank you.
     
  16. D_Hailsham

    D_Hailsham

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    Thanks for Boiler and pump info. I can't find any data on the pump; it's not listed in any Grundfos catalogues. I suspect it's a special for Kingspan - the KIN in the PC number. which is the date of production (2012 week 39), is the clue. But, based on the standard UPS 25-60, a setting of about 4 should be about right. If you find the exit pipe, i.e the one connected to the return, is hot a lot of the time turn the valve to a higher number. The valve only needs to be open when the boiler is running at minimum output.
     
    Last edited: 2 Feb 2019
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