LP automatic change over

[jlandreth]

I have yet to run one of my lp tanks completely empty but I am just about to now. Will I know when the change over happens or does it just occur with out me knowing it has happened. My phone app says I am down to 1% and I keep getting the notifications that my lp tank is low.

[AirMiles]

When the changeover happens, the green/red pressure indicator on the dial will turn red. I then turn the dial over to use the full tank and refill the tank that's empty. Keep watching for the indicator on the dial to turn red to know you have an empty tank.

I always use the curbside tank first. Then when I get the curbside tank refilled, I turn the dial back to the refilled curbside tank. I'm not sure that the auto changeover works in the opposite, streetside to curbside, direction. Occasionally I switch the position of the two tanks if I've used a significant portion of the streetside tank to not have a nearly empty tank on the streetside.

[jlandreth]

I guess I will find out if it works street side to curbside because my street side tank is the one that's down to 1%.

[dznf0g]

The aluminum tanks have a mechanical float gauge sender. The float does not reach the absolute bottom of the tank. Mine reads 1% for quite some time (running fridge, Water heater and stove). Furnace would drain it much sooner, of course.

I had my local propane distributor pull my gauge sender, as it was hanging up against the OPD float. He let me watch and inspect, so I have seen the "guts" of the system.

[uncle_bob]

Hi

The magic tank sensor "runs out" a bit before it gets to zero. It runs out *way* before it gets to 100%. You can run a tank for a couple weeks and still have it indicate "full". A couple of days is doing pretty well when it reads zero. Yes, the top end depends a bit on how the tank is filled. The bottom end depends a little bit on how hot it is out.

Bob

[jlandreth]

I guess I won't be finding out this time about the change over. Son thought he was doing me a favor by taking my tank and having it filled when he took his. Appreciate the gesture but was looking forward to seeing what happened. Btw, it said I had 1% left but when the gas guy weighed it there was 5 lbs still in the tank. Guess this agrees with what others have said.

[azflycaster]

If you would like to see if it works, close the valve on the active tank. The indicator will turn red and your supply of gas should be uninterrupted. After the test, open the valve and the indicator will return to green and gas with be flowing from that tank again.

[jlandreth]

Thanks, I'll give that a try.

[BigSxyWhtGuy]

As a best practice, we don’t operate both tanks open all the time. Only leave our active tank open and the other closed so we are forced to manually operate. During winter last year we blew through our propane running alde. Ended up running dry on propane at one point and had to fill both tanks. First tank switched and I had no clue.

Considering if we are not running Alde, our gas useage is extremely low and we use a tank in about 5 months, who knew we could use both in such a short timeframe during freezing temps 🤷🏽*♂️

[Gsmblue]

I have been using this monitoring system for a couple of years. I change the batteries each spring.

https://mopeka.com/

[billrector]

While we are talking propane, please check your hoses for leaks. I have a 2017 that we recently had out in Utah here s was very cold at night and we went though a lot of propane.

One day while putting back in a refilled tank. I heard a hissing coming from the other tank when I bumped it. I jostled the hose and found I could make it come and go. I discovered I had a small leak in each hose at the back of the Acme connection to the tank. After just two years, the rubber hoses were very hard and inflexible. I was surprised that they would go bad this fast. Check your hoses with a mixture of soap and water.

I took my hoses to a local propane supply company and they made two new hoses while I waited. I went with longer hoses to avoid 90 degree bends. Hoses were about $20 each.

[guskmg]

I have had the swaged fittings on pigtail Acme ends leak on almost new hoses. I feel the swage Leaks are poor workmanship or metal that is not strong enough to hold the swage. I have also had new hoses stop up and not flow. Techs tell me the stoppage is due to a liquid suppliers put in the LPG. My only advise is to pick a well know brand hose that works and stay with it.
guskmg

[billrector]

Originally Posted by guskmg

I have had the swaged fittings on pigtail Acme ends leak on almost new hoses. I feel the swage Leaks are poor workmanship or metal that is not strong enough to hold the swage. I have also had new hoses stop up and not flow. Techs tell me the stoppage is due to a liquid suppliers put in the LPG. My only advise is to pick a well know brand hose that works and stay with it.

guskmg

My new hoses have an Acme connector with an internal “nut” that you can tighten onto the hose with a wrench and socket. When I saw this, I looked at my stock hoses that came with my Airstream to see if they could simply be tightened. Nope....no nut in those Acme connector.

[nickcrowhurst]

When our automatic change-over operates there may be a very short period when no gas flows. This period could be sufficient to extinguish a pilot light, which could then be immediately re-ignited by the surrounding main flame. I can think of no other reason why, when the change-over occurs, my nose detects a very slight LPG contaminant smell in the trailer for a very short period. I can be in the trailer, and if this extremely faint odour occurs, and if I walk outside, I will find that the changeover has just occurred.
This has occurred even with a new replacement change-over device. It happens every time.
Can anyone come up with another explanation? Has anyone else noticed this?
Nick.

[HRTKD]

The propane regulator, with automatic switchover, on my trailer was at least 10 years old. It was acting goofy. On at least two cold nights it didn't switch over properly and when it did, the primary tank still had a lot of propane left in it. I do use the automatic switchover feature, but I also check the tank levels every few days when the furnace is running a lot.

I replaced it with this one: https://www.amazon.com/gp/product/B00OS5MINA

Here are pictures of the old (on the left) and new (on the right) regulators.

[stwaller]

This automatic LP. Change over was one of my newbie mistakes. 2018 IS 23FB - my original LP tank fill from the dealer lasted almost our entire 1st year of Airstreaming. I kept watching for the tank change over, but never saw it turn red, that is , until BOTH tanks were empty in Cades Cove campground in Smoky Mountain NP.

Upon returning home & filling both tanks, I installed the updated Mopeka tank monitor system, reading on my phone. We had this system in place during our month west in September in Yellowstone, Tetons, & Zion National Parks. Heavy furnace use in Yellowstone & Tetons boondocking in NP campgrounds. The Mopeka monitors seemed to be very accurate, & I can recommend them without hesitation.

Steve & Gail

[TBRich]

Originally Posted by AirMiles

...>snip<... I'm not sure that the auto changeover works in the opposite, streetside to curbside, direction. ...>snip<...

The changeover works in either direction. Just keep an eye on the green/red indicator and when it turns red switch to the other tank and it will immediately turn green. No need to physically switch the tanks...just turn off the one that's empty and remove it to refill...the trailer will continue to use from the remaining tank. After refilling re-install the tank and open the valve...and you are good to go.

[Tim A.]

The automatic changeover regulator that HRTKD shows in the pictures is the type we have always had. Since 2002, we have changed it twice due to malfunctioning and/or leakage. For all three units, the indicator turns half red when the first tank is empty. As TBRich says, manually switching to the other tank will turn the indicator green again. Emptying that tank turns our indicators completely red.

If you don't do the manual switchover and ignore the half-red, the second tank will empty completely and you have no more propane. Guess how I found that out.

Nick Crowhurst asked about the gas odor at the time of switchover. We have noticed the same very often. My presumption is that the mercaptans used to odorize the propane are slightly heavier than the propane and, if you don't move the trailer, tend to settle somewhat to the bottom of the tank. Assuming that is true, the last bit of propane out of that tank is quite enriched in the odorant.

Tim

[HRTKD]

I forgot to mention that when the regulator switches to the secondary tank, you don't get 100% of the BTU/hr as the primary tank.

For example, I have the Marshall Excelsior MEGR-253H. The specifications on that model are:
Primary Cylinder BTU/Hr. - 350,000
Reserve Cylinder BTU/Hr. - 200,000

Mine is the high flow version, so it's more than a standard model that has these specifications:
Primary Cylinder BTU/Hr. - 225,000
Reserve Cylinder BTU/Hr. - 150,000

The consequence of this is that if you've automatically switched to your secondary tank and you're trying to run the furnace, refrigerator and the stove/oven at the same time you may not get the level of output you're expecting.

You can review the Marshall Excelsior literature here. It's a PDF.

Testing your gas system requires checking the line to see how many inches of water column you have. I have an analog testing tool. It uses fluid in a tube. Digital tools are available but are a lot more expensive.
Mine wasn't cheap, but I need to make sure the system was working. You could make your own but I wasn't comfortable with calibrating a DIY tool. For anyone interested, I have one from Dwyer that I bought on Amazon (https://www.amazon.com/gp/product/B008FM8O6C).

[bartzstream2]

Originally Posted by jlandreth

I guess I will find out if it works street side to curbside because my street side tank is the one that's down to 1%.

The way the auto-switching regulator works (I believe) is this. Whichever tank is selected is the one used when BOTH tanks have their master valve open. When the selected tank is empty, or its pressure drops to the point it can no longer overcome a small spring/valve within the brass input fitting on the regulator to which said tank's hose is connected, that valve closes and cuts off the outflow (or the possibility of outflow) from the selected tank, and then the non-selected tank becomes the supply for demanded propane. I realized this when I replaced a defective regulator and then tore it apart to see how it worked. One problem I have had several times over 20 years of RVing is propane leakage from the crimped cover on the regulator that contains the selector switch and diaphragm. The regulator body is made of soft zinc alloy and I even tried resetting the crimp with a punch to tighten it up but to little avail. There is a flexible o-ring type seal between the cover and the body for which the crimp provides the pressure to make the o-ring seal functional. Hope this helps, and if I am wrong about any of this I hope someone enlightens me.