The correct gas input pressure for a propane refrigerator, all RV appliances, and most other propane gas equipment is 11" water column. The propane refrigerator is probably the "pickiest" appliance when it comes to input gas pressure. There is very little tolerance in the gas pressure before problems begin. Appliance input pressure is controlled by the regulator on the propane tank. A gauge called a manometer is used to measure this low side pressure. Low side pressure is after the regulator on the propane tank. The pressure in the tank and before the regulator is high pressure and would blow out a manometer.
Since most people don't own a manometer, if you have doubts about your gas pressure, it would be prudent to just replace the propane regulator.
Although the purchase of a manometer isn't a good investment for most people, it's a must buy for anyone expecting to do a lot of work on propane appliances, or someone in an isolated location who needs all the help he can get in troubleshooting. We've made a serious commitment not to do any selling on the Technical pages, but, since manometers are relatively hard to find, we're making an exception here and will tell you that we sell manometers. Go to Miscellaneous Parts if you would like to purchase one. You could also do a search on most search engines to learn how to make a U-tube manometer.
A manometer is a gauge with a rubber hose attached to it. At the end of the hose is a rubber cone made to slide over a variety of fittings. The outer red numbers on the manometer represent inches of water column,while the inner black scale represents ounces per square inch. As you can see in the picture above, 11" water column is roughly equivalent to 6 ounces of pressure per square inch -- less than 1/2 pound of pressure. Not much.
Testing Regulator Pressure. The easiest way to test the output pressure of the regulator is at the range top. Remove a burner, slide the rubber cone of the manometer over the end of the burner valve, and turn the valve on. Sometimes momentarily opening another burner valve to bleed off the initial surge of pressure will give you a better reading. This way of measuring the regulator pressure works good, unless the range top has its own regulator located at the gas line connection point. If this is the case, you will have to disconnect the gas line and with the use of an adapter, measure the gas pressure directly from the gas line.
Diagnosing Refrigerator Gas Problems. Most, but not all, propane refrigerators have a test point to connect a manometer to, located after the gas thermostat and before the burner orifice. Some older gas thermostats have a test point built into their body. A test point is usually a plugged 1/8" female pipe thread hole, but there are other types. The plug is removed from the test point and an adapter is inserted. The manometer is connected to the adapter and measures the gas pressure as it leaves the thermostat. In diagnosing a gas problem, this is the critical point for gas pressure.
Never leave a manometer connection unattended. Since the connection is only a rubber cone over a fitting, it can easily come loose and allow propane to escape at a very fast rate, creating a fire or explosion.
Not all refrigerators have test points and this is unfortunate. The only thing you can do in this case, unless you want to create your own in line test point, is disconnect the gas line at the burner orifice and place the cone of the manometer over the end of the gas line. This will give you the pressure to the orifice, but won't pick up subtle, fluctuating problems.
Testing the Propane System for Leaks. A manometer is very useful for testing the integrity of the plumbing of your entire propane system. This is done by pressurizing the system, turning the tank off, and then seeing if there is a loss of pressure after a certain amount of time.
To test for system leaks, turn off all gas equipment and connect the manometer to a range top burner valve as in testing the regulator pressure, above. In this case, however, a regulator at the range top is not a problem. Open the valve on the propane tank and then close it. Open the range top burner valve to get a reading and then open another burner valve in momentary increments until the needle on the manometer drops to a little below full pressure. The reason for this is the high pressure trapped between the propane tank valve and regulator can feed the low pressure side for quite a while. Record the reading of the manometer and go away for 20 minutes. If, when you come back, the needle has not dropped, you don't have a leak in your propane system. Keep in mind, we turned all the appliances off and have only tested for leaks up to the shut off point of each appliance. This test only tests the plumbing system.
It is considered tolerable for the manometer to drop 1/2" water column in 20 minutes when testing for leaks. If the manometer drops farther, you need to start looking for leaks with a soapy solution. Don't overlook the rubber cone connection of the manometer as a possible leak source.