Auto Switchover Valve

[MK397THR]

Interesting issue today, checked the propane tanks this morning and it had switched over. So I removed the empty tank to take to be filled. Didn’t realize till I got there it was not empty, low yes, not empty. For reference we were not out of the teens yesterday. Wind chill in the single digits. Can that drop the pressure enough to trick the switch valve?

[ncitro]

Interesting issue today, checked the propane tanks this morning and it had switched over. So I removed the empty tank to take to be filled. Didn’t realize till I got there it was not empty, low yes, not empty. For reference we were not out of the teens yesterday. Wind chill in the single digits. Can that drop the pressure enough to trick the switch valve?

Yeah I have heard at low temps its difficult to get all of the propane out of the tank. I think if you switch it back after the tank rests and warms up (while running on the other tank) you can get most of the rest out of it.

[MK397THR]

ncitro Thanks for the reply. Temperature is what I suspected. We are new to this. We also have not had weather like this in middle TN in several years.

[Cate&Rob]

What you have in your “propane” tank is technically LPG (liquified petroleum gas) which is a blend of propane and butane. Propane has a higher vapor pressure than butane. Vapor pressure is what causes the liquid in the tank to change to vapor which can be drawn off . . . but, vapor pressure is temperature dependant. In warmer climates the percentage of butane in the tank is greater to reduce tank pressure. In cold climates the percentage of propane is higher so that it will vaporize. All this to say that a tank filled in the southern US (expecting normal temps) probably has sufficient butane content that the vapor pressure in the tank went very low. If the other tank happened to have a higher percentage of propane or was on the sunny side of the trailer, this could cause the valve to switch over.

Rob