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James A/C Co.
serving Do-It-Yourselfers since 1990.
Satisfying every customer....one at a time!
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Call toll free 1-866-584-0355 or 1-903-759-2160 fax 903-759-4605
309 Patriot Circle, Longview, TX 75604-2240
THINGS TO CHECK IF THE SUCTION PRESSURE IS TOO HIGH:
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Normally, the suction pressure on a refrigerant-22 system will be between 60 pounds gauge pressure (which keeps it above the
freezing point) and about 80 pounds. This depends on the temperature conditions. Make sure the superheat and subcooling are
correct to see what is to be considered normal for the conditions you have presently.
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- Refrigerant overcharge of the system will cause the head pressure as well as the
suction pressure to be too high. The cooling coil will be "flooded" with refrigerant and thus cool poorly, the superheat will
be excessively low or non-existent and liquid refrigerant will be dumping back into the compressor causing it to sweat
excessively. Subcooling of the condenser will be abnormally high when it is overcharged.
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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 evaporator section.
- 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.
- Excessive load on evaporator such as having a 95 degree F. indoor temperature, having
ducts broken or construction misapplications that allow hot attic air into the return ducts or drawing hot outside air into it
will cause high suction pressure. If the blower motor is capable of high volumes, it might be blowing too much air. Usually,
though, this will only show a slight increase in the suction pressure.
- Missing or incorrect piston size in an evaporator piston-type flow control device may be
the cause of high suction pressure. Check the piston size with the dealer and replace if necessary. If the suction pressure
is excessively high, someone may have left the piston out all together. This could happen, but is not very common, of course.
- 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 there in the process. Look for a cooling coil that is not cooling 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.
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
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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. |
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Figure 1 is showing the same valve in the heating mode and is placed here at this time only to show you the other operation
that the valve performs. It is explained more in the Heating section of The Diagnostics Chain |
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