ACtion Magazine - March 2015 - (Page 25)

Recovering the entire charge Blake Gordon H ere in Canada where spring ambient temperatures are often in the 50°F to 70°F (10°C to 21.1°C) range, being able to heat the various components to flash the refrigerant during recovery is a must. With sealers or stop leak being added to A/C systems, it is important to use a filter to prevent these additives from entering your refrigerant identifier. To ensure all the refrigerant that is adsorbed in the compressor lubricant is recovered, you can run the A/C system for 10 minutes. This will agitate the compressor oil so the refrigerant will migrate to the condenser where with heat on the bottom of the condenser will allow for the recovery of the refrigerant that might be in the residual oil. Today with more equipment having the dryer built into the side of the condenser, the ability to heat the dryer is of utmost importance. With a manifold gauge set installed on the system, start the engine and turn on the air conditioning system if possible. If the compressor is not able to be operated due to a clutch failure, we can still recover the refrigerant from the compressor by simply heating it with the hot air gun during the refrigerant recovery process. To prevent the removal of compressor oil from the AC system, only recover refrigerant vapor from the low pressure side of the system until system pressure is at least 20psi (137.9kPa) below the ambient air temperature. At this point, any remaining refrigerant in the system will be vapor and you can begin to recover the remaining refrigerant from the high side access port. If the A/C system has an access port on the high side between the compressor and condenser, you can recover refrigerant right from the start and not have to wait untill the pressure drops. During the refrigerant recovery stage you must have both the dash and (if equipped) sleeper fans operating on high blower speed. Be sure to open the doors so that the air circulates through the cab. You will know the last bit of refrigerant has boiled off or changed state in the evaporators when the temperature of the air leaving the vents is the same as that of the ambient air. Sometimes it is not possible to heat the bottom of the condenser. When this is the case, disconnect the compressor clutch wire or remove the clutch coil circuit fuse. You can then operate the engine and use the engine fan to pull air through the condenser to boil off the refrigerant. Once the pressure in the A/C system has dropped to slightly below zero psi, stop the recovery unit and check to see if the pressure rises. If it does, this is caused by the last bit of refrigerant flashing from the oil in the various components. Start the recovery unit again and recover the last bit of refrigerant. At this point there is always a small amount of refrigerant left over in the recovery unit, so also recover it as well. When hooking up the refrigerant recovery unit, connect the outlet of the recovery unit to the liquid side of the re- covery tank. The liquid remaining in the tank will adsorb the refrigrant that is being pumped into the tank and this helps to keep the tank pressure from rising. After recovering all the refrigerant, shut off the recovery machine and connect a hose between the recovery machine and the vapor port on the recovery tank. Start the recovery machine, open the recovery tank vapor port and the refrigerant in the recovery machine will suddenly move to the tank, completeing the refrigerant recovery process. ❆ Blake Gordon Air Conditioning Trainer for Polar Mobility Research Ltd, Calgary, AB. You can reach Gordon at Reader Reply March 2015 * ACTION 25

Table of Contents for the Digital Edition of ACtion Magazine - March 2015

Engine cooling systems: Electric cooling fan operating strategies
System Charge Determination
Service Port
Leonard's Law
Virtual View
Heavy duty and off road
Last Watch
Coolin Corner
Letters to the Editor
By the numbers
Industry News
Association News
In Memoriam
New Products

ACtion Magazine - March 2015