Why Would A BBQ Regulator Freeze or Have Ice On It?

by grillrepair on March 8, 2013

I saw a question posed to the “experts” at a international service company today and it scares me that someone without real education and experience can be labeled an “expert”in gas appliances without basic knowledge.  A customer went to this service company site to ask the question posed above: Why does my gas grill regulator freeze up and have ice on it? The expert reply was that there must be a problem with the tank; disconnect the tank immediately and refer to the owners manual of the barbecue.  Of course the problem with this is that Kenmore barbecue manuals — nor most barbecue manuals — have anything in them about the check valve or about ice freezing the regulator.

Fortunately you are at Grill-Repair.com by Majestic Grill Parts and we can walk you through whatever problems you are having.

LP stands for liquid propane because propane is a liquid.  Our low pressure gas appliances use liquid propane as a gas because the liquid vaporizes inside the tank so the gaseous form of propane is pulled into the grill (or fireplace, pool heater, space heater, water heater, etc).  Liquid propane is very cold — far below freezing  — and technicians have to be cautious not to burn their hands when filling propane tanks because only a few seconds of propane can severely damage skin and other materials.  The liquid inside the cylinder vaporizers (boils) along the inner circumference on the LP tank and the gases go through the regulator into the grill.

The various sized LP cylinders hold varying amounts of liquid propane and are capable f generating different amounts of gaseous propane fuel.  The “standard” LP tank that we all use was designed to hold 5 gallons of propane but because of the safety features added in the past 10 years the common tanks hold approximately 4.5 gallons.  This common sized propane tank is generally capable of vaporizing enough liquid into gas for 55,000 BTU.  This amount of liquid vaporized into gas varies according to temperature, humidity and the amount of gas in the cylinder.  When the gas tank is 2/3 empty there is a lot of empty space inside the cylinder so vaporized gas can build up inside the reservoir of empty space in the cylinder.  This way even though the liquid is vaporizing gas at the standard rate there is more gas available in the tank.  When the tank is full the vaporization rate is all the gas available.

Most barbecues do not get very hot becaue these appliances are designed to be broilers: designed to heat air trapped inside a closed hood so the accumulated heat can surround and cook food.  Typically gas burners are made to burn 13,000 BTU’s so a 4 burner barbecue will burn  52,000 BTU’s and as much as 67,000 BTU’s if the barebcue has a side burner range top attached to it — assuming the burners are all burning n High and the range top burner is burning on high.

When the barbecue is pulling more gas than the tank is vaporizing the barbecue will usually burn fine for a time but eventually the gas will run out and there will not be enough gas to feed the control valves spitting gas to the burners.  At this point the liquid propane that is cold beyond freezing can be pulled into the regulator and the freezing liquid cannot be used as fuel.  The regulator will become so cold that moisture in the atmosphere will freeze near the regulator and there will be ice crystals and sometimes ice chunks on the aluminum housing of the regulator.

When liquid propane is pulled into the regulator the regulator will stop working.  A regulator is a very simple machine with  a gas line leading in and a gas line leading out and a chamber in between that only allows a specified amount of material through.  The gas chamber has a rubber diaphragm with a spring above it to keep pressure and the spring is set based on the mass of the gas and the pressure to be regulated through the “out” side of the chamber.

If freezing liquid flows through the in-door of the regulator the cold will freeze the rubber diaphragm and the aluminum casing so the gas line stops feeding fuel to the appliance.  Most barbecue manufacturers know to make their barbecue appliances capable of functioning safely and effectively within the range of acceptable vaporization.

The regulator will have ice crystals on it when the gas barbecue is pulling gas so fast the vaporized propane is used up and the liquid propane is being pulled into the regulator.  This can be very dangerous.  The freezing will stop all gas flow so the barbecue will normallyy turn off and it is important to turn the gas and the BBQ control valves off so vaporized propane does not start to flow as the ice melts.  Also it is possible for the internal diaphragm to freeze opened more than the tension spring should allow and a lot of gas will eventually be forced into the burners creating huge flames in the barbecue.  Although I have created this frozen regulator situation many times I have only had the terrifying experience of freezing the regulator open once — and it was terrifying!  I was using an infrared grill and the intense flames from the infrared burner were about 8″ tall and sounded like a jet engine.

If this happens to you — and it usually happens with tank-fueled fire pits or fireplaces more often than barbecues — it is important to turn everything ff and discnnect the tank immediately.  The gas orifices are either too big and allowing too much gas to flow to the burners or the LP cylinder is too small to vaporize enough gas.  When we build custom fire pits that pull 90,000 BTU’s we almost always make the client use a 40 lb horizontal propane tank because a standard tank is half the size necessary to fuel a fire pit burner.  Gas grills designed for 90,000 BTU’s like some of the larger grill models by Solaire, Alfresco and Firemagic come standard with a two-stage regulator which stages the regulation so the grill uses vapors more effectively and the regulator will not freeze or allow liquid to damage the flow.

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