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Discuss What system/boiler set up is this? in the Plumbing Forum area at

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  1. Eddm87

    Eddm87 New Member

    Hi all.
    Need to change a 3port valve, i know how to etc, but I don't understand this system. It's a bit of a hash up in the airing cupboard,



    IMG_7876.JPG IMG_7877.JPG
    thought it looked like a atandard gravity feed system with f and e,
    But then I looked at the boiler which has an expansion vessel and what not.


    What kind of boiler/system is this? How do I isolate and drain The system (not tank)? Also when fitting the electrics do I need to reprogram the system?


  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    sealed system and y plan

    turn the boiler off / controls off

    open the auto air vent black plastic thumb screw / wheel a turn (just until it goes slack dont need to remove the thumb screw)

    you can just drain the system via a drain off and it wont refill (unless your filling loop is open)

    to refill the system once your finished open the port valve to the mid position

    find the silver braid hose by your expansion vessel

    and open the taps / screwdriver slot (like a normal iso valve) increase the system pressure to around 1.5 bar and close the valve

    bleed your rads if you stop getting air out check the system pressure will probably need topping up again keep repeating till you get water out, then move on to the next rad etc

    hope this helps ed
  3. Best

    Best Trusted Plumber Top Contributor!!

    Probably a Y plan system with heat only boiler and heating system has been sealed externally to the boiler.
    The pressure can be dropped fully by using a draincock somewhere on system - on a rad, etc, and it can be refilled using a filling loop that will probably be located near boiler, or in airing cupboard. Usually at least one bar pressure needed.
    You need to learn all this to ensure your system remains topped up to correct pressure and have your gas boiler and the red expansion serviced once a year by a gas engineer
    Speedy Shaun beat me to it. :)
  4. Ric2013

    Ric2013 Plumber Top Contributor!!

  5. Eddm87

    Eddm87 New Member

    Just a quick couple of points...

    Where will I find the air vent as I Gota obv open this to prevent a vacuum. Also, what's the best method to add inhibitor? Put it in a rad?

    This one is a particularly stupid question but if I pressurise it to 1.5 bar when cold, then when it heats up it will go up to 2ish? Or will the expansion vessel take it up and it stays at 1.5?

  6. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Left of the cylinder (brass body)
    And the rad air bleeders

    Either put it in the rad or mag clean (red label left of the boiler)

    And yes 2-2.5 bar when warm
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