Unvented Megaflo Cylinder (Solar), why does it have an expansion vessel?

[Doug0205]

Quick update;

Drained the main cylinder then waited for the EV to drain, although ended up pushing Schrader valve in which sped everything up. Must have still been an air pocket inside that got released when it drained a little? Ominous.

The system is cold and empty, more or less. Tried pumping EV up, got to 2.7 bar, and then it couldn't go up any more (the target being 3.5). Presumably that means something has gone wrong with EV?

 

[Johntheo5]

Are you sure its not the pump, you are looking at the pressure at the pump end?, that should do at any rate for the time being, the recommendatation is the UVC pressure minus 0.2bar so ideally 3.3bar, post the cylinder capacity and the EV size and we can tell what temperature you can go to without exceeding say 4.5bar. When you have the cylinder fully recharged check with soapy water around the EV air end for any air bubbles.

 

[Doug0205]

Are you sure its not the pump, you are looking at the pressure at the pump end?, that should do at any rate for the time being, the recommendatation is the UVC pressure minus 0.2bar so ideally 3.3bar, post the cylinder capacity and the EV size and we can tell what temperature you can go to without exceeding say 4.5bar. When you have the cylinder fully recharged check with soapy water around the EV air end for any air bubbles.

Yeah, it's a newish double piston bicycle pump with max pump of 4bar roundabouts. Will not be using one of those again to do this as nearly broke my ribs. I'll have to try with another one.

These pics should have relevant info.

Cheers

 

[Johntheo5]

OK, you're good to go, 25L EV & 210L UVC. after a full reheat to 60C from a minimum of mains temp of 15C the final pressure will be 4.4bar and if reheated to 65C, final pressure of 4.6bar.

Those pressures will only decrease to ~ 4.3bar & 4.4bar if precharged to 3.3bar.

 

[Madrab]

Yes - If the pump isn't suitable then it will be difficult to pre-charge the EV properly.

Though, I do have to stress, this work isn't really within the realms of the DIY'er.

Unvented cylinders are regulated products and only when they supply instructions on the side of the cylinder, say giving the steps to re-instate the internal bubble, is it ok for the end user to perform. Any other works should really be performed by someone that is qualified to do the work, especially if it is solar enabled too. Not doing things properly cause cause more problems than it sorts.

 

[MeldrewsMate]

It's quite stiff with the bike pump (foot). Decided to drain the system and do a reboot, as it were.


As above, decided to a "reboot" and drain cylinder, try and recharge EV, then refill and get a service before it all goes back on. Got a feeling the EV might be bust, but who knows.

It is clear that you are not willing to follow simple instructions; so be it.

 

[Doug0205]

It is clear that you are not willing to follow simple instructions; so be it.

All sorted, cheers.