Fitting extra expansion vessel

[al4567]

I have a Vokera compact combi boiler. It has trouble with pressure and venting the water when the temperature is set higher than a certain level, and even if the EV has failed, it's probably on the minimum size limit for the house anyway.

Therefore, given that the EV is totally buried in the back of the boiler, I reckon an external EV is the easiest way to sort it out.
But........... why have they got a filling loop on them? I've seen explanatory diagrams showing them close to the mains water feed, but I want to tuck mine away somewhere convenient. Do I just leave the existing filling loop where is is on the boiler, ignore the one on the EV, and T the EV in where I want to?

 

[gas4you]

Yes, just tee the EV in where convenient, preferably on a return.

Use the existing boiler filling loop and PRV.

 

[al4567]

Thanks Dave, any particular reason to use the return? Doesn't really matter as I can get to either where I want to site it, but wondered about the reasoning behind that choice?

 

[corgiman]

I have no idea why it goes on the return, I have always fitted on the return

 

[screech]

the instructions normally say they should be fitted on the return

 

[TheGasMan26]

Its to maintain positive pressure on most of the pipwork to prevent air being drawn into the system.
If its fitted on the flow wen pump starts the vessel soaks up some of thepump pressure & may leave the system under negative pressure.

 

[al4567]

That sounds like a very good explanation! After a bit of thinking, I reckon I can position it very close to the boiler and on the return no problem. Close to ideal I believe??

 

[boabcelt]

Also if the vessel is fitted on the return it is exposed to slightly lower temperature and this will marginally increase the life of the membrane. In theory.

 

[TheGasMan26]

Also if the vessel is fitted on the return it is exposed to slightly lower temperature and this will marginally increase the life of the membrane. In theory.

Never even thought of this, good point.

 

[oilman]

Its to maintain positive pressure on most of the pipwork to prevent air being drawn into the system.
If its fitted on the flow wen pump starts the vessel soaks up some of thepump pressure & may leave the system under negative pressure.

This sounds like a desperate attempt to provide a complex reason, however unlikely.

 

[gas4you]

I've always done it so that there are no zone valves etc between it and the boiler

 

[oilman]

Surely that would apply where ever you put it.

 

[ddk]

splash out and put 1 on the flow and another on the return! in theory it should be better on the return but I bet it wont make a difference!