REGULATED propane backfeed to external LPG port?

[khocke]

Anyone try running their Interstate’s propane appliances & genny off a regulated external 20 pounder plumbed into the external LPG quick connect port, say at 11” pressure or so? I’d switch the internal tank’s solenoid off.
There’s no propane schematic in the interstate owner’s manual and I haven’t crawled underneath to try reverse engineering the system.

[ITSNO60]

Interesting idea. I wonder how the 2 stage regulator on the Interstate would react to the backfeed pressure?

[InterBlog]

Not via a direct OEM connection, no (our older Interstate doesn’t have that feature). But we did re-plumb so that we could accept external sources of propane. Blog post describing the work here, plus a 25-second video:

https://www.youtube.com/watch?v=kZtMTmR_RYo

[khocke]

I’ve seen that post of yours, InterBlog, when searching for a solution. Your parts listing is great.
There’s a posting on the FB Mercedes-Benz Sprinter RV's page where ppl have had success plumbing regulated LPG back into the aux port, but they were not Airstreams. For the cost of a quick-disconnect to male flare fitting, and some parts borrowed from my BBQ, I might give it a try after reading up some more on how propane regulators (like whatever’s installed on the Interstates aux port) handle reverse flow.

[GammaDog]

I do that with my trailer. I have two 30 lb LP tanks in the tongue and travel with two 20’s and two Honda 2000s on a roll out platform under the tonneau of my truck.

All are plumbed with the same QC fitting as the Airstream has (MB Sturgis 250 1/4”). I carry a tee fitting (M/FF) and a double male adapter. The later required to quick connect the F end of an extension hose to the F connector on the trailer.

You can make up those adapters from standard brass plumbing supplies. I think they are 1/4” NPT. Be sure t use the yellow, gas rated Teflon tape.

[earljones458]

I had an Airstream XL 390 motorhome we used at a winter lot in Crystal River, FL. We used a T Adapter that connected between the fixed propane tank and the line into the coach that allows an external slave tank. That allowed us to use the slave tank instead of unhooking and driving to a propane station to refill. They are on Amazon. Search propane tank adapters for RV slave tank.

[khocke]

Originally Posted by khocke

Anyone try running their Interstate’s propane appliances & genny off a regulated external 20 pounder plumbed into the external LPG quick connect port

Responding to my own question: Yes, this works - on my ‘22, anyway, using the cheapo regulator/hose borrowed from my BBQ. Needed a 3/8” flare union to connect it to the external BBQ quick connect hose that came with the coach. With the internal propane switched off, and external port valve on, I was able to run genny, furnace and both range burners at the same time.
Dunno how useful this is, I don’t plan on traveling with a spare tank, but there you go.