Superheat generally does not affect actual oil return to the compressor crankcase unless the superheat is set so high that it causes a starved condition resulting in low return gas velocity or evaporator icing. Low superheat at the compressor results in liquid refrigerant being present in the oil sump. The violent action of liquid refrigerant boiling in the crankcase will cause oil to be blown out into the system resulting in low oil levels. Liquid refrigerant in the compressor’s pressurized lubrication system will result in a loss of net oil pressure resulting in an oil failure trip, bearing damage due to the loss of lubrication to bearing surfaces and possible valve damage due to liquid slugging caused by the returning oil.
To learn more, download the Principles of Refrigeration Superheat.
Here is a general listing of possible causes of oil failure trips:
To learn more, download Oil Pressure Problems in Refrigeration Systems
Maybe you missed air throw and air distribution. Evaporators are intended to be Non-ducted but airflow and throw is an important factor to consider. Usually unstable product temperatures are directly related to Evaporator coil selection, airflow restrictions and air throw.
These are typical symptoms of an improperly selected nozzle. Liquid temperature at the expansion valve not only affects nozzle selection but also affects the TEV selection since colder liquid has more capacity. Typically nozzles and expansion valves are selected based on the BTU capacity of the condensing unit divided by the number of evaporators, 95°F. ambient and 105°F. condensing with a 90°F to 95°F. degree liquid temperature. If the liquid temperature or the design condition change the selection may not be correct for the application. Consult an Application Engineer.
My evaporator feeds okay for a while then the suction pressure drops to the point the low-pressure switch cycles the compressor off. For some reason the blockage clears on its own then repeats itself. I have changed the expansion valve but I still have the same problem. Is it possible to get two bad expansion valves in a row?
Chances are there was nothing wrong with the original valve. All indications point to a wet system. The expansion valve will feed until the saturated suction temperature reaches 32F the freezing point of water. The wet refrigerant and oil will block the TXV until the internal temperature reaches the melting point and the blockage clears. The remedy is good service and installation practices to ensure a clean dry system. Recover the refrigerant, replace the driers and oil if its POE, evacuate to 500 microns or less and recharge. This problem should go away provided the system is clean and dry.
There could be many factors, but the most common is the transformer tap is not plugged into the spade that closest resembles the incoming voltage. Set the 208/240 tap on the transformer accordingly
All units sold by Heatcraft Refrigeration Products are covered under the standard catalog warranty. The basic terms of the standard catalog warranty is as follows:
To view all Warranty information, visit our Warranty page.
Whenever possible, replacement parts are to be obtained from a local authorized Heatcraft Refrigeration Products wholesaler. Replacement parts which are covered under the terms of our warranty statement will be reimbursed for total cost of the part only plus applicable taxes. The original invoice from the wholesale parts suppler must accompany all warranty claims for replacement parts reimbursement. Processing or handling fees assessed by parts wholesalers are not reimbursable under Heatcraft's warranty terms.
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