How can I tell if my heating and cooling system is low on refrigerant?
If the system just isn’t putting out much cold air it could be caused by low refrigerant. Although it can still put out some cold air with half the required refrigerant, the output is reduced and the system is much less efficient (and costs more to run). Poor cooling doesn’t mean for sure that the refrigerant is low, other issues could exist.
If your system has a sight glass (which is a glass bubble window) then you can look to see if the system is full or empty. If the glass looks empty and there is no cold air coming out of the system, that means that the system has lost its charge, through a leak or it has never been charged correctly. If you see bubbles that means that the system is low on refrigerant but still has some charge. In this case the system needs to be charged with new refrigerant.
Of course, the most accurate way to measure refrigerant is with a set of gauges that you attach to the system. Professional heating and cooling service techs always carry these. The gauges measure the pressure on both the high and low side of the system; the pressure of the refrigerant right after it leaves the compressor and after it has traveled through the whole system. The correct pressure is different for different systems and usually a reading of less than 160 pounds at 80 degrees farenheit, on the high side and less than 22 pounds, also at 80 degrees on the low side, means your system is low and needs more juice.
Other warning signs include oily streaks around the compressor, or wet areas around hose connections could mean you have a leak. Although the system is supposed to be closed with no escaping refrigerant, many older systems may leak a few ounces a year, and after a number of years you might need to give the system a little shot of refrigerant. If your system needs recharging on a yearly basis, or more often, you have a leak that should be tracked down and repaired.
This is done through the use of soap bubbles. If it is a fast leak, use of an electronic leak detector or injection of dye into the system pinpoints the location of the leak.
Leaks are most common in the piping connections, and valves and most easily repaired in these locations. The most difficult leaks to repair are those in the evaporator coil. Coil leaks are usually not repairable and require replacement of the evaporator coil or the installation of a new unit.