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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 HEAD PRESSURE IS TOO HIGH:
| If it is determined that a system head pressure is over 400 pounds, immediately turn off the system until a cure of this problem is implemented. |
- Dirty condenser coils is the number one cause of this problem. On a 100 degree day with a refrigerant-22 system it is not likely that the high side pressure will be over 300 pounds on any of the equipment made in the past 10 to 15 years. Some will operate as low as 250 pounds. You will have to check the subcooling to be sure WHAT is too high a head pressure. Look at the high side gauge temperature conversion and subtract from it the temperature of the LIQUID line (measured with a good thermometer) and this is the subcooling amount. Remember that you want 10 to 20 degrees subcooling.
Many times I have found an outside unit who's coil fins have been so badly bent and damaged that the head pressure is "absolutely out of sight". Careful work with something like a small screw driver and a good fin comb will correct much of this problem, but it is very tedious and takes hours of hard work. Fin combs come in many sizes and each comb is made to fit a certain number of fins per inch. Get one or two of the plastic type from your dealer that is made for your unit. Measure the number of fins per inch carefully.
- Extra hot indoor temperature will cause the head pressure and the suction pressure to be abnormally high, too. If the indoor temperature is 85 to 100 degrees, then the unit will have high pressure for a while until the indoor temperature gets back down. Check the return air duct to make sure it is not pulling hot attic air from a broken duct or something else like that. Ideally, you can check pressures really well when it is 80 degrees indoor. Most charts for charging are based on this temperature.
- Refrigerant overcharge is a very common occurrence and results in high head pressure as well as high suction pressure. Check the subcooling to verify this condition. If you need to remove refrigerant, you should contact a dealer with appropriate reclaiming equipment to extract it for you. Sometime if the evaporator coils were to be iced or if charging took place in cool weather, an inexperienced person or a careless technician may add gas to the system to raise the suction pressure, but it results in an overcharge. When the coils thaw, excessive head pressure and higher suction pressure will be present.
I have even seen condenser coils so clogged that it no longer condenses the liquids in sufficient quantity and the evaporator will starve for refrigerant giving an indication that the system needs refrigerant. If you were to check both high pressure as well as low pressure with the gauges, this mistake will be avoided.
- Refrigerant flow restrictions can occur and may be the result of pinched or kinked refrigerant lines. Filter, filter/driers, or Catch-Alls
® can also become restrictive if the system contains a large amount of contaminants, non-condensables or foreign matter.
- Non-condensable in the refrigerant can be a major problem. If you suspect water in the refrigerant system, stop here and call a qualified technician. He may be able to save your unit from an early death. The refrigerant from the system will need to be removed and a very good vacuum will have to be performed. Regassing of the system and installation of suction and liquid line filter/driers will have to be done. The system will have to run normally for a week or more and then the driers will have to be again removed or replaced to assure the system in perfectly clean. The oil in the compressor may even have to be removed and replaced. This is no time or place to experiment.
- Condenser fan motors can become electrically shorted and will run at a much reduced speed and thus give inadequate flow. Watch carefully for this.
- Recycling of condenser air is not as common, but occurs too often. The discharged air from the condenser must not incur objects for at least five feet. Sometimes, units are positioned too closely underneath overhangs or will have been enclosed by structures and the hot exhausted air will return to the condenser. This results in excessive head pressure. Move the unit or the structure.
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