Normally, the suction pressure during cooling, with a refrigerant-22 system, will operate between 60 pounds gauge pressure (which keeps it above the freezing point) and 80 pounds or more. This is for the cooling mode, but what about in heating pressures? This depends on the temperature conditions. In the winter time, the pressure and the temperatures will be below the freezing point a lot of the time. The outside unit will ice and it will automatically cycle into a defrost condition to attempt to remove the ice every 30 to 90 minutes. So if the suction becomes high, there is likely a serious problem.

• Refrigerant overcharge of the system will cause the head pressure as well as the suction pressure to be too high. The outside coil will be "flooded" with refrigerant and thus evaporate the refrigerant poorly, the superheat will be excessively low or non-existent and the liquid refrigerant will be dumping back into the compressor causing it to sweat excessively and will likely be noisey. Subcooling of the refrigerant in the indoor coils will be abnormally high when it is overcharged.

Remember, that if there is a serious overcharge of refrigerant, the high side pressure may be at a dangerous level. Check it the minute you turn on the system and if it is above 400 pounds gauge pressure, turn the unit off and reduce the refrigerant charge. You will need to contact a dealer for this so that he may reclaim the refrigerant.

• Check-valve leakage in a heat pump system will by-pass refrigerant around the expansion or flow control device in the indoor section. However, the check-valve in the outside unit will be attempting to force the refrigerant to flow through the expansion valve or flow control device there. If the check-valve is leaking refrigerant around (instead of through) the TXV (thermostatic expansion valve), then you will detect a temperature drop through the body of the check-valve. The suction pressure will increase and the heating indoors will suffer.
• Inefficient compressor suction valves will cause varying degrees of higher than normal suction pressure, depending on the amount of damage they have experienced. They are extremely difficult to diagnose and will require a good technician. Your solution to the problem is a new compressor or new condensing unit, thus a considerable amount of money is involved. Don't guess at this one. Eliminate everything else first. Then call your best technician if you suspect the valves in the compressor.

• Execssive load on the indoor coil such as having a 95 degree F. indoor temperature. Some people (especially some older people) like a really hot house in the winter time.

• TXV stuck open (see explanation in orifice-flow control device in Refrigerants and Charging) will cause an unusually high flow of refrigerant into the low side of the system and will, of course, give higher than normal pressure in the process. Look for a heating coil that is not heating well and a compressor that is being flooded with cold liquid refrigerant. It will likely be sweating all over and making laborious chattering sounds. The superheat will be non-existent or excessively low. You may as well replace the TXV (thermostatic Expansion Valve), but you may also take it apart and lightly clean all the moving parts. Don't forget the "push-pins".
• Four-way solenoid valve leaking is fairly uncommon, but check for it. It does happen. Only the heat pumps will have the 4-way valves. The hot gas from the compressor goes directly to the indoor coils and the four-way valve routes the refrigerant in the outside coils to the suction line of the compressor. If, for example, the suction pressure at the compressor is high and the suction line got warmer as it passed through the four-way valve, the you will have leakage of the high pressure hot gas into the suction side of the system.

This image is showing the 4-way valve in the cooling position. The compressor discharge is routed to the outdoor condenser coils and the gas from the evaporator





is routed to the compressor suction tube. This particular valve is operated in the cooling mode by energizing the solenoid. It is not energized in the heating mode. When checking a 4-way valve you must learn if it is energized in cooling or in heating. Simply turn on the unit and feel or listen for a distinct click of the solenoid valve movement or you may can tell by the wiring diagram. If neither of these is successful, contact a dealer or manufacturer and they will gladly give you the information.

Figure 1 is showing the same valve in the heating mode. Notice that the hot gas is sent to the indoor unit and the outside coil is sent to the suction line of the compressor.

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