Seeking Insight On A Odd Issue. (Propane Tanks)

[Todd_P]

My 5th wheel has two tanks with one on each side. The main regulator and changeover valve is on the left and a red regulator is on the right. One tank is full, the other is roughly half, and a third tank is empty.
So now for the issue....

When the third tank was on the left and emptied it automatically switched, as it should, to the right tank. The system ran off the right tank with no issues and a new full tank was placed into the left position.
Once the right tank reached about half, propane began leaking from the furnace and either the regulator or tank would hum or oscillate when propane was used. (Yes things were evacuated before testing, no need for safety police comments!)
Switch over to the full tank on the left and the issue goes away; no hum and no leak from the furnace.
Now it gets weird...
Swap the position of the tanks so that the half full tank is on the left and the full is on the right. Run off the left and there is no leak from the furnace but there is a slight oscillation.
Switch to the full tank now on the right and there is no leak from the furnace but there is a pronounced oscillation/hum/ring.

My current theory is that there is something wrong with the half full tank and it also damaged the red regulator on the right side. I am leaning to replace the right side regulator and have the half full tank recovered, inspected, properly purged, and refilled if it checks out good.

Figured I'd reach out here to see if there might be a different view of it.

[Cate&Rob]

Creating a propane leak at the furnace seems like a curious result of changing tanks about. I would suggest a pressure check with a manometer, in the various tank configurations, looking for something causing downstream pressure differences. Normal pressure is 11” Water Column.

BTW, I added “Propane Tanks” to your title to make this thread searchable in the future.

Rob

[Scott'n'Wendy]

Well...propane tanks regardless of fill state supply the same amount of pressure...so atm, I'm not sure it is tank dependant. How do you know you had a propane leak at the furnace? Snoop? Smell? Inside? Outside?
Humming to me would indicate the regulator being the problem...but I'm not sure right now with the info at hand as I understand it.

[Todd_P]

With the bottle in question on in the right position, you can smell gas coming from around the furnace, any other configuration does not cause this. It is odd.

[Cate&Rob]

The red regulator on the right tank holders a higher pressure (30 psi) in the long cross-over hose to the selector low pressure regulator on the left side. Correct feed pressure to all devices is 11” WC and can be confirmed with a manometer T’d into the output of selector pressure regulator. With this, you can try the different tank configurations looking for an over pressure combination. Can you narrow down where the furnace leak is coming from? This should not be happening at any time.

Rob

[TedS]

Seems reasonable to suspect the partially full cylinder as the problem follows it. There are several valves in series, the cylinder valve's check valve, the pigtail's excess flow valve, the pressure regulators, the furnace valve. They may be interaction resulting in the oscillating sound. The 'leak' may be due to incomplete combustion somehow caused by the oscillating pressure and flow. Check the offending cylinder's outlet check valve. In some open space open the cylinder valve, there should be no gas flow if the check valve is working properly. I would not suspect the regulator valves since they work with the full tank in either position. The same would hold true for the furnace valve. This would be a start.

[TedS]

There is also a float valve as part of the cylinder valve. It senses the liquid level. During the filling process it shuts off to prevent over-filling to preserve the vapor space at the top of the cylinder. Maybe it is wonky( another engineering term).

[Todd_P]

Good info, I'll see what the results are.