Many if not most TT’s with dual LP gas bottles now a days have an Auto Change over LP gas regulator. This device makes our life easier in the middle of the night when it’s really cold out or a during a torrential down pour and the LP tank we where using just went empty.
It switches over to the other tank automatically for us and gas service is unaffected.
There can be a lot of discussion some times on, do we use these, don’t want to use these because... and how to they work? And if you are like me, until you read up on these things and see them working, you really do not know how they work. And sometimes after reading, one still has questions. Since this auto switch over regulator operation comes up from time to time, I thought I would attempt to explain how the systems works from the way I know it and how I use it. Anyone seeing anything not posted correct here, please jump in and help us sort it out.
Mine just switched this past weekend and saved me from getting up in the middle of the night to go out and change tanks.
And we have another post by Happy Campers where questions came up on how are they suppose to work, so here goes.
Here is picture of the auto switch over regulator
The regulator is actually a 2 stage regulator where the 1st stage takes full tank gas pressure that can be up in the 100 to 150psi range in the summer down to about 5 to 7 psi pending the exact model. Then the 2nd stage regulator takes it down to 11 inches of water column pressure or approx 0.5 psi to use inside the TT. The 2 stages help make it more stable across a wider range of fluctuations.
It also has internal check valves and a selector lever where it can join 2 tanks and allow you to select which tank works as the “in service” tank and the “in reserve” tank.
On top of the regulator is a colored indicator below the black cap. The cap stays on normally. It has a red and green color showing below the black cap. When the tanks are hooked up and still turned off, the indicator is red indicating no gas pressure or not enough, is detected inside the regulator:
See here for the Red indication.
Now you have to select which tank you want to use first. So you flip the selection lever until the knob of the lever is on that tank side. In this pic, the lever is towards the hose that I want to use that tank first as the “In service” tank. By default the other tank is then the "in reserve" tank.
I then open the in service tank 1st, watch the indicator move to green and then open the reserve tank. Or I can just use the in service tank if I only want to use one of them for a short time. Slowly the gas pressure will rise and the red indicator will turn green if the in service tank has adequate LP gas in it. Looks like this:
I always wait once I turn on the in service tank for the green indicator as if that tank is empty, it will never turn green and then I know I have an empty at the start of camp.
As the in service tank drains down to empty from use, and if the reserve tank valve is open and has adequate gas, the system will auto switch over inside to the reserve tank. Note: The selection lever is still pointing to the empty original in service tank that is now empty. The reserve tank now become the in service tank. The indicator will show red as the tank that the selection lever is pointing to is empty.
You then flip the selection lever over to the full tank and it is now the new in service tank. If the selected tank has enough gas and pressure in it, the indicator will then turn green once again. If not it too will show red.
There are check valves in the regulator to allow you to remove the empty tank, refill it and then put it back in service even while the other tank is using gas. But only do so once you flip the selection lever and the indicator goes green.
If a switch over occurs and the tank it is switching to is empty, (now you have 2 empty tanks
) the indicator will remain red when you flip the lever.
The debate has been that if you use this system in full automatic that you forget about it and then you can come up with 2 tanks that are empty at once as there is no alarm. Some combat this by only opening 1 tank at a time. This works but can also be cold in the middle of the night or your fridge stops working if your on LP mode or the power goes out.
What I do is monitor the tanks often and track my gas use. Unless the furnace is running, we do not use very much gas on only the fridge, stove or HW heater. I always start using the tank that is selected and see if it turns the indicator green when we start camp. If it is, then I turn on the 2nd tank. An empty tank at the start will show red and then I know it.
A tank can last us several months. But when using the furnace, I check every morning. I also look down the side of the tank for condensation when the furnace is running in cool weather. I can tell how much is approx in it. When it gets close to 1/4 full, it might switch that night if the furnace is on. Every morning then I do a quick check on the tank indicator and if I’m green, I’m good for another day. If it is red, then I know next camping trip I have to get it filled. Or if the trip is a long time, get it filled in the next day or so.
The key to not running out is you have to be diligent about looking at the level. If you do not check, well you can end up with 2 empty tanks.
See this link for the Marshall Brass auto switch over regulator and more info. It has 4 links on there that show how it works and how to test it. http://shleggitt.com/edlees/index.html
While we are on LP service, the green nut that screws the pig tail hose to the tanks is also a safety device. It will only allow so much gas to flow pending it’s size. The black nut is for smaller systems like a BBQ, the Green nut is larger like the entire TT and a Blue colored nut is even larger then a TT. If a large hose leak or gas valve breaks and opens a large surge of flow, the black/green or blue nut will shut down gas flow to a trickle as a safety device. Since it does this, there are 3 different sizes for different usages so you do not get false trips.
Hope this helps