Back-feed Propane through external LPG port – anyone do this?

[greghoro]

Many if not all recent Airstream trailers have an external low pressure LPG port to power such things as grills, fireplaces, etc. Mine has a shutoff valve as well as a quick connect female fitting and has a warning not to exceed 25,000 BTU.

I’m thinking that this would be an ideal way to provide propane to the trailer for such situations like hooking up a large tank for a stationary campground host or to use a separate tank for preheating a trailer the night before travel so one could leave with a full complement of propane on board. Note, it is NOT a means to fill the on-board tanks but a way to run the on-board appliances. My furnace is 25,000 BTU, so just on the border.

One would have to make sure that a low pressure regulator is used in the setup, which one could purchase relatively cheaply from a hardware store for a propane grill. With appropriate low pressure hoses and male quick connect fitting, one could plug it right in to the trailer.

Anyone do this? Or think of a valid reason why it couldn’t work? Could the on-board trailer regulator be damaged or somehow protect itself by venting if it is back fed (although a valve at the trailer regulator to isolate it could mitigate that)?


Greg

[rmkrum]

The only issue I can see is that you would have to put a male connector on the outlet side of your 'extra' regulator to mate with the female quick connect on the AS, in other words, backward setup to normal...

That would be a safety hazard if the tank is turned on by accident with the regulator ONLY connected to the tank--propane is going to come out freely. I suspect that there is some code violation present as well...most propane quick connects have a safety check valve ONLY in the female part of the set that closes when you disconnect. All mine have a manual valve on the pressure side of the quick connect female for additional safety...

A safer way to do this would be an extra connector (male) on the AS, with a properly rated propane check valve behind it and a manual cut-off valve before the gas gets to the AS supply line. Then put a proper female quick connect on the regulator output port. The manual valve AND the check valve would prevent a gas leak when you are running on the AS tanks.

I don't think running 'normal low pressure' on the output side of the AS built-in regulator is an issue--after all, gas does not back up through that regulator when you change out tanks, etc.

Since I happen to have a 'spare' male quick connect laying around, and the idea of easily connecting an auxiliary tank to my AS in cold conditions is appealing, I'm going to steal this idea, and find an appropriate 3/8" propane check valve...

I'm already adding a female connector for supplying my dual-fuel inverter generator propane from the AS, so it's not that big a plumbing nightmare to add an auxiliary input port as well. It would work with the hoses and lash-up I already built for the generator. I need to find a way to rig some "crunch" protection to the extra plumbing on the A frame. A nice sturdy steel plate to keep errant rocks off the plumbing and support the fittings is probably also a good idea...

EDIT: On a quick look for a propane check valve--nothing on Amazon, so this might be a slight stumbling block.....

[JMynes]

I have done it.
My portable BBQ has a male qd connector on it. The propane is supplied by a 20 lb tank, low pressure regulator, and a hose, on the end of which is a female qd connector.
I bought two male qd ends and a coupler, taped and screwed the three pieces together, and presto! I can now connect female propane supply hose to female Airstream.
I hooked it up, checked for soapy bubbles, and operated each propane appliance successfully. Furnace, water heater, stove, and fridge all simultaneously.
I did not run the appliances for a prolonged period. The tank may frost up with extended use, but it works at least in the short term.

[rmkrum]

Heh, that's an even easier way to do it--less parts!

Just put a valve between AS tank regulator and rest of the trailer...

[JMynes]

Originally Posted by rmkrum

Heh, that's an even easier way to do it--less parts!

Just put a valve between AS tank regulator and rest of the trailer...

Why would you need that valve?

As you said previously:
I don't think running 'normal low pressure' on the output side of the AS built-in regulator is an issue--after all, gas does not back up through that regulator when you change out tanks, etc.

Just plug it in and use the portable tank.

However, in the interest of avoiding litigation;
I don’t recommend or endorse this method as a viable means of supplying propane to your trailer.
Always check for leaks on all fittings.
Don’t try this at home.
In fact, it’s a bad idea.

[rmkrum]

The double-male adapter suggested, when plugged into the female quick connect is an instant leak...at least on my AS it would be easier to turn a manual valve rather than opening up the tank cover and shutting off both tanks...(I'm lazy)

[JMynes]

There's a valve right behind the female connector on the Airstream. At least there is on mine.

[OTRA15]

I bought the parts to do this, but have not had the time or good weather to hook it up to the BBQ 20-pound tank. To be conservative, I think I would turn off the main propane cylinders while checking things out, although that is probably not required.

We run our Yamaha 1k gen off the AS's low-pressure port, and bought an additional BBQ tank regulator etc. setup so that this gen could also run off a BBQ tank. Just needed a couple of short male QD connectors joined by a coupling, as I recall, to mate things up.

Photos coming in the Spring -- wind chill here in the NE is minus 10F right now!

[rmkrum]

Originally Posted by JMynes

There's a valve right behind the female connector on the Airstream. At least there is on mine.

Yeah, that one is to isolate the quick connect fitting from the line that feeds from the AS tank regulator and the rest of the AS appliances. It's there as a backup to the valve inside the female quick connector that shuts off gas flow when you separate the male quick connect.

The valve I'm proposing to add would be to cut off gas flowing from the AS tank regulator to the rest of the system before the quick connect. For my lazy butt I'm putting it in so I don't have to fiddle with opening the cover and shutting off both AS tank valves...