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Old 07-28-2011, 07:22 AM   #11
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KyDan's Avatar
Join Date: Mar 2008
Location: Louisville, KY
Posts: 5,648
On a previous trailer on a COLD late fall middle of the night-
I had only turned on one tank valve.
Naturally the LP ran out in the wee hours of the night.
I got up and tossed on some clothes and went outside and spun the
valve open on the 2nd tank. It was full.
I went back inside and found the furnace was not working.
I lit a stove burner and got a small flame.
I went back outside and shut the tank swapped positions with the
empty one and tried it again and it worked.

In retrospect I'm pretty sure I just opened the valve on the full tank
too fast and the safety valve shut it off or nearly off.

On my home back patio gas grill, if I turn on the burner 1st and then
spin open the tank valve it will occasionally trigger the safety valve
and when that happens I get a low flow and small burner flame.
Cure is to shut the burner off and shut the tank and wait a second
and then open the tank slowly and everything is back to normal.

I don't know what the website says about the safety valve but my
real life experiences are that they do shut the tank but not all the way.
Many folks have posted here over the years that had the same thing.
Low flow rather than no flow seems to be the norm when the safety
valve is activated usually by spinning the hand valve open too fast
on a system that has no pressure.

Dan & Rita D
2004 5.3L Silverado 1500 ext. cab 2WD
1999 Suzuki Intruder Motorcycle
Blue Ox WD hitch, AirLift load levelers

Camping days 2010-53, 2011-47, 2012-41,
2013-41, 2014-31, 2015-40, 2016-38
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Old 07-28-2011, 07:45 AM   #12
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Join Date: Sep 2008
Location: Virginia Blue Ridge Foothills
Posts: 9,272
Dan, just speculating here, but your incident could also be be caused by the "flow limiting device". There is an explanation on that with my #7 post link.

If you turned on the 2nd cylinder, and the furnace was still calling for propane, then the flow limiting device will not open fully. It needs back pressure to completely open. Somewhere between swapping cylinders, maybe the furnace shut down and was no longer calling for propane, the system had enough back pressure, and the flow limiting device fully opened. Even an open oven pilot light valve is enough to trigger the flow limiting device into not opening fully.

Of course, it could have been just as you said.....the tank was opened to fast allowing the OPD to shut off the flow on a full that case my long winded explanation above is a moot point.

Ideally, the OPD should shut the gas off entirely, and only close when the tank gets full at filling. That is because once a pigtail is screwed onto the tank, the OPD valve should stay open, regardless. Of course, that is theoretical.

The flow limiting device will give a low flow situation if there is not proper back pressure.


Chap , DW Joy, and Fur Baby Sango
2006 Ford F150 Super Cab 4x4
2008 Surveyor 263
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