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Valliant pressure vessels and F75

Discussion in 'Plumbing and Central Heating' started by trevorbayliss, 11 Feb 2020.

  1. trevorbayliss

    trevorbayliss

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    I have been loosing a little pressure from the Eco tech plus 837 (12 y/o) combi. Say 0.3 bar over a week. Ive been topping it up over a 2 months.

    Checked the expansion vessel the other day. Drained down the pressure in the boiler, but it wouldn't drain below 0.9 bar. Pumped up the EV to just under 1 bar using my bike pump with a pressure gauge on it. Opened the valves and filled back up. All ok and running at 1.5 bar.

    That was on sunday. So heating working sunday and monday all ok.

    This morning the heating didnt go off. F75 fault.

    I switch off the boiler and put a tiny bit of water in, then switched on. All started working fine and is running now.

    I have googled some issues and i wonder if the issue is the pressure sensor.

    Or have i done anything wrong when putting air into the EV ?
     
  2. Theweeknd

    Theweeknd

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    When you drained down the system did you leave it opened ended when pumping the EV ?

    Most likely you have a fault pressure sensor as it should have showed 0 bar when drained down.
     
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  4. trevorbayliss

    trevorbayliss

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    I think I closed off the drain tap and then pumped it up.

    I only drained one side as the return side was harder to get to

    pressure now while boiler off is 1.9. So it has jumped from 1.5 on Sunday when I set it back up
     
  5. muggles

    muggles

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    The drain needs to be left open whilst setting expansion vessel pressure, but more importantly you shouldn't be opening the casing at all unless you are Gas Safe Registered. It forms the safety room seal on your boiler, and the Regulation 26.9 checks need to be carried out any time that cover is removed.
     
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  6. DIYnot Local

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