Evening all, today I came across a real curve ball that some one out there may have encountered before.

I went to a rinnai infinity ( near new vt26) today that would not ignite, after checking it had gas I removed the cover and went to remove the test point on the gas valve, and as I cracked the test point I was greeted with a liquid, water like in colour but it had a smell to it and it seamed like a really high pressure coming out of the test point.... I left it just cracked for nearly a minute before the pressure subsided and I could completely remove the test point screw.
This was really odd as I had the gas turned off under the unit, this is a lpg bottle installation.
I then attached my manometer and it went from 0 to 27 kpa in less than 30 seconds ! that's not a typo! 27.3 kpa to be exact.
I went back to basics and tested the gas supply from the lpg regulator.. it had a static pressure of 3.02kpa.
after nearly 3 minutes I reattached my manometer to the manifold test point and it was at zero, so I fired the unit and it started.
then I turned it off and once again the pressure climbed back up to 21kpa !! I said what the fudge???
a quick call to Trevor at rinnai and he had heard of this before but only once., the customer had completely emptied the bottles and he believes that there may be a fluid in the bottom of the lpg bottle that has moved up into the gas valve and expands as it turns back to a vapour !!!
now that's really odd.... what gas does that?
Any way after a discussion with Trevor I decided to remove the manifold and check for fluid, and found nothing, but an odd metallic sort of smell, so I blew air through the gas valve and reassembled it, the gas/ fluid that I was dealing with was trapped between the first solenoid and that's where the test point is on a rinnai and after that is the 2 solenoids for high and low control.
so this fluid/vapour was trapped and would expanded and then the solenoids could not open.
does anyone have any idea what this gas is? there is no way a gas valve can increase the gas pressure by itself, it has to be a fluid that is expanding as it turns back to a vapour, but how can it move along a pipe and into a appliance then expand again???
 


Linkback: https://forum.plumbers.nz/instantaneous-water-heaters/67/real-curve-ball-infinity-issue/1725/