by Jack Bradshaw – Foretravel
The primary advantage of the absorption refrigerator over the compressor refrigerator is the ability to operate on more than one type of energy source, namely 115 vacs, LP gas, and some 12 VDC units. The electrical model requires virtually no maintenance as far as the boiler is concerned. The electric element is just a resistance heater that produces a specific amount of heat to boil the refrigerant upon the command of the thermostat. If the heating element does not heat, it must be replaced; however, heating elements are long-lived. Their failure is normally the result of over-voltage caused by plugging into an improperly wired outlet, or by a runaway generator or lightning strike.
The LP-gas mode, however, does require some attention. In order to produce the proper amount of heat at the boiler, several things must be right. The LP-gas regulator at the tank must provide 11 to 11 Yz inches of water column pressure. Higher pressure can damage the cooling unit and produce excessive carbon from a richer mixture. Low pressure would cause poor cooling and possible failed ignition at higher altitudes. The new regulators are preset and should deliver the correct pressure for several years. After about five years, however, it is a good idea to have a service technician check the pressure and reset it if necessary. The next item in the LP-gas operation is the orifice often called the jet. This is a restrictor with a very small but very precise hole that permits the correct volume of gas to flow into the burner.
The hole, or the orifice, is predetermined for that particular size cooling unit in order to give the boiler the correct amount of heat. Over time, the oily, waxy impurity in propane, and possibly some microscopic metal flakes from the gas manifold, may contaminate the orifice and restrict the volume of gas, which would then not produce the proper amount of heat, affecting performance.
To check the LP heating components, remove the outside cover and gain access to the burner. Operate the refrigerator on gas and observe the flame. If the flame is not well defined or is lazy, this would be an indication of very low gas pressure or a very dirty orifice. A well-defined flame will have a prominent and erect blue cone over each one of the burner slots. A moderate amount of orifice contamination is not distinguishable by visual observation; so, while the technician is checking the gas pressure, have him remove and clean the orifice. For you to do it yourselfers remove the orifice and clean it with alcohol. Just rinse thoroughly several times and blow-dry with an air hose. A jeweler’s loupe or magnifying glass will be needed to inspect it after cleaning to ensure that no debris remains.
Some maintenance should be performed at least once each year. Although propane is a relatively clean-burning fuel, it is a hydrocarbon; therefore, it does leave some carbon residue. This is usually a slight accumulation on the ignition electrode, the thermocouple, and on the inside of the flue tube and spiral baffle. After months of operation, any accumulation might grow sufficiently to ground out the electrode and cause the burner not to light at the most inopportune time. Any debris falling out of the flue tube could contaminate the burner and reduce the amount of heat available, resulting in poor or no cooling. Use a small screwdriver to remove any carbon from the electrode and thermocouple which is directly above the burner and slightly into the flame. Ensure the air gap between the electrode and burner is 1/8 to 3/16 inches. Use 20 to 30 psi and blow all the debris away from the burner area, out of the burner barrel and up the flue. It’s important to use low air pressure only, as you do not want to blow the spiral baffle from its position in the flue. Be sure to look up through the vent to ensure nothing obstructs the free upward flow of warm air from the back of the cooling unit.
The proper gas pressure, a clean jet, a clean burner, and a clean flue will give the right amount of heat in order to produce the optimum available cooling.