Fitting a new external expansion vessel

[danfre]

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

 

[Milleniumaire]

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!

 

[Steelmasons]

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?

 

[ollski]

Does anyone have experience of the following model of expansion vessel:

Reliance - Aquasystem 18 Litre Heating Expansion Vessel & Bracket XVES100050

I like the idea that the membrane can be replaced and I assume this is done by unscrewing the silver top, although it's not obvious where the valve is located - usually on the opposite side to the pipe fittings? I assume expansion vessels can be fitted either way up, although I've seen some that seem to be "top" connected and floor standing.

Most examples of EV's I've seen on the web seem to be fitted high up the wall, with the pipe connections at the bottom and all the pipework running downwards (this is the case with my potable hot water EV), but I'm aware you can get floor standing EV's, so I guess it isn't a requirement to have them "high up". Is the fitting hight related to having a certain length of pipe running to the EV to allow the water to cool as the membrane may be affected by very high temperatures?

I've also wondered how an EV is vented as surely air will collect in it over time?

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?

 

[danfre]

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

 

[Milleniumaire]

.... nobody isolates a boiler to repressurize the vessel

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?

.... Why 18 litres?, what was wrong with the size of the original in the boiler?

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.

 

[Terrywookfit]

Why 18 litres?, what was wrong with the size of the original in the boiler?

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.

 

[Milleniumaire]

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.

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!

 

[Steelmasons]

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!

Really???