Hot Dawg Gas line question

[gary the cobra]

Gentlemen:
I have installed a Modine Hot Dawg HD75 heater in my shop. I am in the process of pressure testing the propane line with air pressure. I have pumped it up to 40lbs pressure with all valves to the heater open. Overnight my pressure gauge dropped from 40lbs to 20lbs. I blew it back up to 40, painted the connections with soap and water and I can see no leaks (bubbles). My questions are: First, how many pounds pressure should I blow this up to for the test? Second, is this 20lb pressure drop normal? I am not too sure when I install 120gallon propane tank how much pressure the tank will deliver to my heating unit. Do you think I still have a leak, or does the heating unit itself bleed off some pressure? I am using black 3/4" gas pipe for my lines into the heater. Your advice would be appreciated.
Gary

 

[Bill K]

Gary I'm not sure if the're the same, but when we do pressure test on gas fireplaces both natural and propane we keep the valve closed at the unit. High pressures can damage the control valve, not sure if the same can happen to the hot dawgs.
Bill

 

[drbill]

Natural gas or propane will have a regulator. I just checked my gas companies web site for pressure of natural gas delivered to my house, it's only 1/4 psi. Propane I think is only 1/2 psi after a regulator. So I think your 40 psi is over kill and it might of dropped from a temperature difference or leaked through the heater it's self. I don't think the poor control valve in the heater was meant to be put under so much pressure.

 

[Ron Lombardo]

Gary when we test gas lines we test it up to 5psi with a LOW PRESSURE GUAGE and the appliance gas valves closed. They are only made to run at max 1/2psi or 7" Water Column.

Ron

 

[gary the cobra]

Thank you guys for the replies,sounds like I tested the lines at too high of pressure.Hope I did not damage the control valve,Guess I'll find out when I fire it up after the county inspects the install.