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Loop question

Discussion in 'Plumbing and Central Heating' started by brianjbox, 13 Aug 2011.

  1. brianjbox

    brianjbox

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    Hi all

    I'm helping a mate move his oil fired central heating boiler and hot water tank into an adjacent room and studying the existing pipework, well there's this loop with valve that we can't work out it's function.

    I've outlined the loop in white, it has nothing coming off the back of it.

    [​IMG]

    Some more of the system [there's ton's of it]

    [​IMG]

    Just planning the pipework for the new setup and can't see why we need three valves.

    Help/advice appreciated as always :D

    Thanks
    Brian
     
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  3. picasso

    picasso

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    looks like a motorised bypass, it could be wired in to open with the pump over run, I cant see any other reason for it, unless its there to increase the flow, do both valves open at the same time ?
     
  4. brianjbox

    brianjbox

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    Thanks for the speedy reply :D

    I only got involved when their oil fired burner packed up [rusted through], that's been removed and a new one sourced, I'm unfamiliar with their system so don't know how it operated but can investigate further.

    I just couldn't work out what the loop/valve did unless it works in conjunction with the other one, if working opposed they seem to cancel each other out :confused:

    Another weird thing is the central heating pump off the top of the immersion tank,

    [​IMG]

    This I have been told runs all the time the boiler is on and pumps hot water to the taps whether they are turned on or not, there are no flow switches or anything, is this right?
     
  5. picasso

    picasso

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    the bronze pump should be on a timer, there is no flow switch because it circulates hot water on its own loop, its to give instant hot water at the furthest taps, must be a fairly big house, maybe there wasnt enough flow with one 22mm 2 port valve so they cut in another one ?
     
  6. Nige F

    Nige F

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    Is it 1 a big house , 2 owned previously by an engineer - ;) Not that long ago I changed a oil boiler for a M8 - there was this big industrial valve thing in a similar scenario - manual though - and it did sweet FA :LOL: Wasn`t even brass for scrap- re piped and the lot worked better.
     
  7. Agile

    Agile

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    As suggested it MIGHT be a motorised bypass. Thats an unusual idea though. East to check, put onto CH and feel the two levers and they will NOT both be floppy.

    But I am very convinced that they will be operating in parallel, both floppy together.

    That will be a good solution because the pipework is 28 mm and the valves are only 22 mm.

    The valves create a considerable restriction and so two in parallel will give more flow rate as they will have half the restriction than just one valve.

    Tony Glazier
     
  8. bengasman

    bengasman

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    Looks like a botched design to me.
     
  9. gasafengineer

    gasafengineer

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    Those motor valves are 28mm installed in parallel , the reason for using two is due to cost as a 42mm motor valve with seperate actuator would cost in excess of £600 as opposed to two 28 mm valves @ a cost of £180.
     
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  11. Boilerman2

    Boilerman2

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    Gassafeman has hit the nail right on the head
    it is 2 valves in parallel - to increase flow rate to what must be a large heating ciruit it is NOT a by-pass if it were it would be connected between th Flow & Rturn!!! :rolleyes:
     
  12. Onetap

    Onetap

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    There may have been two zones (upstairs and downstairs?). The pipework below the valves branches; at some time it may have had the two pipes connected to the two valves. In this case there would/should have been one thermostat for each heating zone and a 3 zone time-switch. The unidentified flying wiring end might have something to do with this.

    The use of solder ring and end-feed fittings also suggests that at least two different installers may have been involved.

    Although a possibility, this still wouldn't explain why the two zone heating system was abandoned; maybe a bodge by someone who didn't understand the system when the timer packed up.
     
  13. bengasman

    bengasman

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    I sincerely doubt that.
    Both valves come together in one pipe of what looks suspiciously like the same diameter as the pipe coming out either valve.
     
  14. gasafengineer

    gasafengineer

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    :rolleyes: :rolleyes:

    Those motor valves are fed via a 35mm tee reducing to 28mm for EACH valve , even if both valves were fed via a 28mm tee the two MV would better than one due to the resistance trough each valve , this is quite normal practice yesteryear & today , i've used this method plenty of times in the past.

    Have you got your argumentative head on today? :D , certainly not doing yourself any favours.
     
  15. bengasman

    bengasman

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    I noticed that, and was referring to the pipe where the two come together. Looks to me like the very same diameter as before the junction.
    If the system is so large that it needs a flow pipe of 35 mm, it must be a pretty big place.
    If that is the case, splitting in 2 to ensure sufficient flow, and then immediately after that come together and continue as one 28 mm pipe does not seem like a partiuclarly clever way of doing things.
     
  16. gasafengineer

    gasafengineer

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    It comes together in a 35mm tee spliting to two floors :rolleyes:
     
  17. brianjbox

    brianjbox

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    Wow, thanks for all the replies guys :D

    The house is a very large house [looks like a row of terraces], my friends bought it 15 years ago as a project and still trying to sort things out.

    This shows the pipework below the valves, the two 15mm tails going through the wall do a couple of rads at the front of the house. The larger pipe coming out of the wall above is the flow pipe from the boiler the other side, we started marking pipes up as we identified them ;)

    [​IMG]

    These are varied shots of the pipework we're trying to sort out, the tank and boiler are being relocated to the other side of the wall [pantry] and we're trying to improve the performance of the system and ding out stuff not needed.

    [​IMG]

    [​IMG]

    [​IMG]

    We're using a Grant boiler [don't know ref number off hand] with four 28mm connections, it's not new but both the replacement and original one only had two out of the four connections used :confused:
    As far as I can tell you have a flow and return, vent and cold water supply, why have previous plumbers on both systems not connected the vent pipe and cold water supply to the actual boiler but instead connect these into plumbing afterwards and plugging the boiler? is there any advantages in taking vent and CW supply back to the boiler so all four boilers connections are utilised.

    Much appreciated this guys

    Brian
     
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