Propane Tanks & Furnaces

[Onespeed405]

I have a question regarding propane tanks and my RV furnace.

This weekend, I had 1 full 30lb propane tank and one 2/3 full (30lb) propane tank on an automatic switch over valve. I had the switch over valve pointing to the 2/3 tank with the tank turned on. I left the full tank turned off. (I intended to turn it on later)

All propane appliances were working fine, except the furnace. The pre-blower would turn on, the burner would ignite for about 8-10 seconds, then fail and shut down. I lived with this the first night.

In the morning, I turned on the valve of the full tank, but did not touch the switch over valve.

Poof, the furnace worked as normal.

As it turns out, for the whole weekend, we still had 2 pounds left in the first tank and never dipped into the full one.

Anyone have an idea of what is going on here? I have been RVing for 30 years and have done this many times (running with one tank open).

[Onespeed405]

Thanks so far gang...

Just to further clarify...

There was a already a half day of full demand on the propane.
- hot water heater (always on)
- fridge on propane setting
- 3 burner stove and oven was used
- furnace trying to light


The switch over never turned red all weekend. It was turned toward the "in use " tank.

(New info)
Prior to the weekend I filled the spare "not in use" tank, hooked it up, but never turned it on. Maybe the lack of pressure on that side of the line mattered.

I also took off the "in use" tank to weigh it. (2/3 okay) Put it back on line, but (and I already knew better) I did not turn it on slowly. I did not think I tripped the OPD since water heater, fridge, stove worked fine.

Huh???

[Old-Biscuit]

Me Again wrote:
eHoefler and Old Duck got it right!

Given the 2007 year trailer age, I would not think you have the troublesome red regulator on the far side tank. Many have problems with those.

Chris

Close.....
It's NOT the Overflow Protection Device (OverFILL Protection Device---OPD) That is inside the propane cylinder and is a 'float' mechanism that shuts off flow when filling cylinder....set for the 80% max level.

The 'Excess Flow Device' is what trips when opening a propane service valve too fast. It is inside the big green nut (ACME Nut). It is a spring loaded ball check valve that moves towards close when first opening valve........then as pressure downstream in system 'equalizes' the ball moves back to center position.
Opening valve too fast causes an inrush and ball check valve closes. TO reset you close service valve, bleed pressure off and then slowly open service valve

[Me_Again]

eHoefler and Old Duck got it right!

Given the 2007 year trailer age, I would not think you have the troublesome red regulator on the far side tank. Many have problems with those.

Chris

[RollandB]

Interesting, shutting off, bleeding off then opening the values slowly is exactly what Weber told me when I had the same problem with one of there grills. It worked.

[eHoefler]

Close the tank valves, bleed off the pressure, then open the valves slooooooowly. You most likely tripped the Overflow Protection Device, which will restrict flow to a trickle at best.

[NMDriver]

Old-Biscuit wrote:
Furnace didn't light off 1st night just to not having enough propane flow thru furnace line.
After operating other propane appliances...propane system flow established demand placed LP regulator

I agree with Biscuit.

I understand your thoughts on keeping one valve closed so you do not completely run out of propane, BUT IF you can remember to check the red flag every day or so you can save yourself from needing to open the other tanks valve in a dark, cold night, wearing flip flops and a bath robe (or less).

Just watch for the red flag and take the empty tank to get filled.

[path1]

We have a 2013 model and the automatic propane switch over works sometimes and other times it don't. And I've read its manual many times.

I'm keeping my eyes open for somebody junking an old trailer or 5th wheel and get one of the old style ones that we never had any problems with from the 90's.

[Old-Biscuit]

1st cylinder valved is 'primary' use cylinder.........auto swap regulator will not swap to other cylinder until 1st one goes empty (looses pressure).

Lever pointing to in service cylinder.......that is what resets RED/GREEN Flag.

Furnace didn't light off 1st night just to not having enough propane flow thru furnace line.
After operating other propane appliances...propane system flow established demand placed LP regulator