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Fitting a new external expansion vessel

Discussion in 'Plumbing and Central Heating' started by Milleniumaire, 23 Feb 2017.

  1. danfre

    danfre

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    Put it very high up in the loft, vent by taking cap off and depressing schrader valve
     
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  3. Milleniumaire

    Milleniumaire

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    We don't have a loft space as such as the loft was converted to a bedroom. I thought the EV had to be close to the boiler and connected to the return pipe? I assume this is because the return near the boiler will contain the "coolest" water on the system?

    I've just been looking at a useful image of the internals of an EV and I'm struggling to understand how depressing the schrader valve will remove trapped air from the wet side of the EV, unless of course the membrane is split and then you would get water coming out of the valve!
     
  4. Steelmasons

    Steelmasons

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    EV position is relative to the placement of circulator and not temperature.
    Have you not discussed these points with the 'installer'??..if not then why?
     
  5. ollski

    ollski

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    Just fit it where theres space preferably on the return, make sure you can access the valve to top it up. You don't vent an EV, you fill it with air after the nitrogen has gone.
    Theres no difference recharging a vessel on the system or the boiler, nobody isolates a boiler to repressurize the vessel. Why 18 litres?, what was wrong with the size of the original in the boiler?
     
  6. danfre

    danfre

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    The post was in jest, you have had advice on here from some very knowledgeable plumbers/rgi.
     
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  8. Milleniumaire

    Milleniumaire

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    I thought the boiler flow and return vales were closed and the boiler drained to re-pressurise an internal vessel? Isn't that isolating it?

    I've been having pressure problems with the boiler for some time and although the internal EV hasn't failed, both my fitter and Vaillant technical support have recommended installing an external vessel. 18 litres is required to match the system size and boiler output and was chosen by my fitter. This also allows for the failure of the internal 10 litre vessel and is adequate on its own.
     
  9. Terrywookfit

    Terrywookfit

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    If there is room why not...You can't oversize !!
    Most boilers are fitted with a vessel that is sized to fit in the boiler regardless of system volume.
     
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  10. Milleniumaire

    Milleniumaire

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    That's exactly why I've been told I'm having problems with the pressure in my system. The Vaillant ecoTEC plus 637 system boiler I have is rated at 12 to 37 Kw, but the internal vessel is 10 litres! So, you put this in a 5 bedroom house with some underfloor heating and voila - pressure problems!
     
  11. Steelmasons

    Steelmasons

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    Really???
     
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  12. DIYnot Local

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