Vaporization and cold weather. Episode fifty-two of the Gas Service Animated series.

Here's the LP fact that explains a whole season of no-heat calls: the tank isn't just storage — it's the vaporizer. Every Btu the house burns must first boil out of that liquid, and boiling takes heat the tank can only borrow from the winter air. Cold weather doesn't just chill the customer; it throttles the fuel supply itself.

The engine is the wetted surface — the tank wall that's touching liquid. Heat soaks through that steel to boil the propane, so vapor capacity rides on three things: how big the tank is, how much liquid is in it, and how cold the air is. Big, full, and mild makes endless vapor. Small, low, and frigid makes a fuel shortage with gas still in the tank.

Run the bad case: a five-hundred-gallon tank down at twenty percent on a zero-degree morning, furnace and water heater both calling. The little wetted surface can't borrow heat fast enough, boiling lags the draw, pressure sags — and the appliances starve while the gauge still shows fuel. That's the cold-weather capacity collapse, and it looks exactly like a bad regulator until you read the tank.

The tank tells on itself: frost. Boiling steals about a hundred eighty-four Btu per pound from the liquid, chilling it below the air, and moisture frosts a line right at the liquid level. A sweating or frosted band is the overdraw signature — the tank is being asked for more vapor than its wetted surface can make. Read the frost line like a gauge.

The cure is sizing to the load, not the calendar. A tank picked for annual gallons can still be too small for the connected Btu on the coldest morning — the tankless conversion that doubled the draw, the shop heater added last fall. Size the container and the regulators to the full simultaneous fire at winter design temperature, and the collapse never starts.

And the cheap fix: keep winter levels up. The same tank at sixty percent has triple the wetted surface it had at twenty. Winter fill scheduling isn't a sales pitch — it's capacity engineering with a delivery truck.

When load outruns any reasonable tank — commercial kitchens, crop dryers, temporary heat — the industry adds a powered vaporizer: a heat exchanger that boils liquid on demand instead of begging the weather. That's licensed, engineered territory, but you should recognize it and what it implies about the load.

Don't confuse the two winter villains. Vaporization collapse is the tank failing to make gas — frost at the liquid line, sagging tank pressure. Regulator freeze-up is the pressure cut icing its own valve — frost at the regulator, tank pressure fine. Same symptom at the burner; opposite fixes. Look at where the frost is.

Vaporization in one breath. The tank is the boiler; wetted surface is the engine. Cold plus low level collapses capacity, and frost at the liquid line is the confession. Size to the connected load, keep winter levels up, and read where the frost sits before you blame a regulator. Next: the conversion.