Dermot uses 40 X 58mm evacuated tubes connected indirectly via a plate heat exchanger (PHE) to his existing tank. The PHE is a side-arm heat exhanger and works in a similar way to the more expensive Willis Solasyphon.
Dermot uses a low power 12v dc pump.
His panels are good quality Ejai Solar panels and are the same make as George Row's panel.
Post by leonardermo on Nov 11, 2013 5:49:46 GMT -5
My system has been working away for the last three years with a few fairly minor hitches however I've noticed lately that for some reason,air is entering the system.This becomes obvious when the pump changes tone as the air reaches it. I've had to bleed this air out through the air vent on the panels several times now.The system is holding pressure fine and the only explanation I can think of is that the air is seeping in from the presure vessel through a ruptured membrane. Has anyone any ideas?
Dermot, This is of little use to you but my system did the same thing. I would bleed the system and thing would be fine for a while then the air would return and reveal its presence just as you describe. Then it stopped and I haven't heard a thing for ages. Your leaking membrane theory fits well but would the safety valve not have lifted by now as the 'spring' of the EV is gone?
I suppose there might be a little comfort in knowing that you are not on your own.
Have you at any stage had to top up the system fluid and/or the EV air?
I've had a leaking joint, leak almost undetectable due to high temperature evaporation, and then the EV compensates somewhat. the point at which fluid was leaking/evaporating was also allowing air ingress. Brown stain indicates where leaking was occurring. In my case it was at the pump.
the only real way of testing the EV is to drain the system down (or at the part of it next to the EV if you can do this, and recheck the air pressure on the schrader/car valve. if it has dropped from what you had originally set it to, it will either have been through the schrader (car valve). This can be checked with soapy water., If it's not the schrader, then the suspicion points to the balloon/membrane. if the air pressure has not dropped ( when measured when no fluid in EV), then the EV is not suspect.
well in my case the fluid eventually leaked to the extent that the EV guage was reading zero. i believe that the leaking happened only when the fluid was very hot (higher pressure), and when the loop cooled a partial vacuum may have been created (as the EV was no longer exerting pressure on the system), possibly allowing / sucking air in through the same route as water had originally escaped.
Even if the above theory is incorrect, it would seem reasonable to first check the air pressure in the EV to confirm it is ok (requires draining the EV of liquid), and if it proves to be fine then address the leaking seal at the pump.