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

that would be what it is Robbo but there  is no heat in the gas valve to generate the expantion, and this was at 10 am in a cool cimate.
when I got to this unit and tried to start it there was no ignition, yet 27kpa inside the gas valve. odd aye?

Are you in an area that freezes?

Was this the first instance of this happening or had the home owner had the problem a couple of times before calling you?

having said that, this has to be a case of a gas that forms for either compression/decompression  or heat/cold...