IDK if this is going to get any responses, but if you have any experience with using propane with a portable generator maybe you can explain what's going on.
So I got a big generator, I previously only used gas, but as this was new and dual fuel, it seemed like propane might be a big win. Propane as far as I know doesn't get old like ethanol gas does, won't gum up small engine carbs like gas does.
However, it had some downsides - the tanks are not able to just have an extra gas can to refill while the generator is running if needed, and for some reason I can't tell the manual gives 0 estimated runtime with propane, but lots for the gas fuel. Ok, well some searching found a Y connector with a kind of switch/indicator that is supposed to auto failover to the second connected tank if the first one empties so you can then change out the tank while the generator is running.
Now my problem. Power goes out last night, it's 20F and I fire up the new generator for the first time. First hour, no issue, however it then starts almost stalling out and then restarting over and over again. I go look at it seems like the "switch" indicated it tried to change tanks but... maybe didn't? It went straight up and down, not pointed to the other side (though IDK if I actually understand the switch, there were like 0 instructions with it from Amazon). OK, I'll just figure out which tank is empty (wondering how it went empty in like an hour on a 20lb tank) and move the switch to the other one and then change out the tank with my spare. Did all this, no change. Cannot get the generator to run right, and cause constant brownouts to my house and the generator makes a sound like it's backfiring every so often. I give up on backup power for the night.
Today, I go look at it again, and it starts up and runs fine today at 43F. However I haven't put a load on it, but it wasn't running right without a load last night, so I don't think it was overloading the generator (and I know it wouldn't given earlier uses when it was warmer). OK, well lets at least use the valves on the top of the 20lb tanks to test the switch over thing. I tried turning off one of the tanks (right), the one the switch / arrow is pointing towards. Nada, generator keeps running, switch doesn't do anything. I turn off left and generator stalls out. Weird. I then reset, restart, and try turning off the left tank - no change keeps running. I then re-open left and close right, no change, generator keeps running. Just to not lose my mind, I also close left and as expected generator stalls out.
Ok, so - do I have a worthless amazon transfer thingy, is the propane just not working at 20F or below? This seems really weird as I have a 500 gallon tank for my entire life for heat and stove and it got down to like -15F a few times with no issue.(I asked my provider, they say they can't hook up the portable generator, or even provide me a propane hose / valve/ anything I could hook it up to.) The 20lb tanks are brand new... So some googling seems to say maybe the tanks need to be warmer? I could get some tank heaters I guess and plug them into the generator also assuming it can run long enough for the heater to do anything and bootstrap stuff when it's cold. However, I'm also concerned about not having any estimate how long it should run from what should be 40lbs of propane. I don't know if the first tank leaked over the months since I set it up (the other 2 didn't), but 1 hour seems really fast to run out, and I would expect at least 8 hours when the gas tank is supposed to be good for 18.
So - do I just give up on propane for this generator? It seems silly to keep propane for the warm months and then switch to gas for the winter...
I bought a 22KW propane generator. It's supposed to be plumbed to a large tank, but due to the pandemic I could not get the 500 gallon tank plumbing installed (county permit office was issuing for "emergencies only"). So I tried a 20# cylinder. It iced up after 6 minutes and the generator stalled shortly after. So I bought a 100# tank. That ran for 5 hours until the generator stalled. The tank was still 1/3 full.
What's happening is that there's insufficient area for heat transfer. The propane has to vaporize, so it draws heat from the part of the tank in contact with the liquid. The environment provides that heat, but in a small 20# tank there's not enough surface area to transfer the amount of heat needed to vaporize the quantity of propane required by the generator. The propane stops vaporizing once its temperature drops below the boiling point, and the generator starves. The 100# tank has the same problem when the propane level drops, reducing the surface area in contact with the liquid propane. In the large horizontal tanks, the propane is in contact with a large surface area, and the tank is supported off the ground to provide good air circulation.
Your options are to buy a bigger tank or provide more heat to the small tank. What worked for me was an old washtub filled with water. I put the tank in it, then left the garden hose trickling water into the tub to keep the water from freezing.
If you do opt for a large tank, buy a reconditioned one. They're half the price of new and last about as long because older tanks were made with thicker steel. Buying will save you money because you're free to buy from the cheapest supplier. Buy your propane in the summer when the price is low. Get a tank big enough enough to last the whole year. When you lease a tank, the leasing company is the only one that can fill it, so you won't be able to shop around for the cheapest price. Mine paid for itself in 2 fills (compared my bills with my neighbor who leases their tank).
Your explanation makes sense to me, an uninvolved spectator with no particular knowledge of generators.
Maybe you direct the generator exhaust over the exterior of the tank? Would that be adequate heat?
My thought was to recall that my 20# propane tank has some sort of safety valve integrated into it that will clamp outflow if there is too big a surge in flow. Flow needs to be 0 for a minute or so for it to reset. But that doesn't explain your experience with the larger tank.
Using generator exhaust is inviting overheating the tank. I've been around one when the relief valve pops, and that's a big fire waiting for a spark. It doesn't take a lot of heat - maybe 30 watts - to keep the pressure up. They make tank wrap heaters specifically for this purpose. But I needed power (this was during one of California's infamous "Public Safety Power Shutoffs" used to avoid wildfires). So I used what I had; a washtub and water.
The standard 20# tank has only one safety device - an overfill protection mechanism that prevents filling the tank more than 80%. The propane regulator for portable propane appliances is where the flow limiting device is located. That heavily limits the flow of propane if it detects insufficient backpressure on the outlet side of the regulator when initially pressurizing it (turning on the tank valve).
I have no issue with the 500 gallon tank. It has plenty of surface area in contact with the propane and good air circulation around the entire tank.