Evacuation and Leak Detection
Due to the smaller molecule size of HFC’s, they will tend to leak more readily than CFC’s. Consequently, it is of the utmost importance that proper system evacuation and leak detection procedures be employed.
Copeland recommends a minimum evacuation to 500 microns. In addition, a vacuum decay test is strongly recommended to assure there is not a large pressure differential between the system and vacuum pump. Good evacuation processes include frequent vacuum pump oil changes and large diameter, short hose connections to both high and low sides of the system preferably using bronze braided hose.
Leak detection can be carried out in the conventional manner.
If HCFC or CFC tracer gas is used, care must be taken to completely remove all traces of the gas prior to introducing HFC’s.
Electronic leak detectors are now available that will sense HFC’s. This is considered preferable since it removes the possibility of chlorine remaining in the system after leak testing with HCFC’s and/or CFC’s. There is a view that even small quantities of chlorine may act as a catalyst encouraging copper plating and/or corrosion and should therefore be avoided.
WARNING:
HFC-134a has been shown to be combustible at pressure as low as 5.5 psig (at 350˚F) when mixed with air at concentrations more than 60% air by volume.
At lower temperature, higher pressures are required to support combustion. Therefore, air should never be mixed with HFC-134a for leak detection.
Within the last several years, manufacturers have developed fluorescent dye leak detection systems for use with refrigerants. These dyes mix with the lubricant and, when exposed to an ultraviolet light “fluoresce,” indicates the location of leaks. Copeland has tested and approved the Rigid “System Safe” dye and found it to be compatible with the compressor materials in systems.
Leak Testing
After all lines are connected, the entire system must be leak tested. The complete system should be pressurized to not more than 150 psig with refrigerant and dry nitrogen (or dry CO2). The use of an electronic type leak detector is highly recommended because of its greater sensitivity to small leaks. As a further check it is recommended that this pressure be held for a minimum of 12 hours and then rechecked. For a satisfactory installation, the system must be leak tight.
Line Insulation
After the final leak test, refrigerant lines exposed to high ambient conditions should be insulated to reduce heat pickup and prevent the formation of flash gas in the liquid lines. Suction lines must always be insulated with 3/4" wall Armstrong “Armaflex” or equal. When required, Liquid lines should be insulated with 1/2 inch wall insulation or better. The insulation located in outdoor environments should be protected from UV exposure to prevent deterioration of insulating value.
Evacuation
CAUTION:
Do not use the refrigeration compressor to evacuate the system. Do not start the compressor while it is in a vacuum.
A good, deep vacuum pump should be connected to both the low and high side evacuation valves with copper tube or high vacuum hoses (1/4" ID minimum). If the compressor has service valves, they should remain closed. A deep vacuum gauge capable of registering pressure in microns should be attached to the system for pressure readings.
A shut off valve between the gauge connection and vacuum pump should be provided to allow the system pressure to be checked after evacuation. Do not turn off vacuum pump when connected to an evacuated system before closing shut off valve.
The vacuum pump should be operated until a pressure of 1,500 microns absolute pressure is reached — at which time the vacuum should be broken with the refrigerant to be used in the system through a drier until the system pressure rises above “0” psig.
NOTE:
Refrigerant used during evacuation cannot be vented. Reclaim all used refrigerant. EPA regulations are constantly being updated. Ensure your procedure follows correct regulations.
Repeat this operation a second time.
Open the compressor service valves and evacuate the entire system to 500 microns absolute pressure. Raise the pressure to 2 psig with the refrigerant and remove the vacuum pump.
Refrigerant Charging Instructions
1.Install a liquid line drier in the refrigerant supply line between the service gauge and the liquid service port of the receiver. This extra drier will insure that all refrigerant supplied to the system is clean and dry.
2.When initially charging a system that is in a vacuum, liquid refrigerant can be added directly into the receiver tank.
3.Check equipment catalog for refrigerant capacity. System refrigerant capacity is 90% of receiver capacity. Do not add more refrigerant than the data tag indicates, unless the line run exceeds 25ft. Then, add additional refrigerant as per the chart on page 30. Weigh the refrigerant drum before charging so an accurate record can be kept of the weight of refrigerant put in the system.
4.Start the system and finish charging until the sight glass indicates a full charge and the proper amount has been weighed in. If the refrigerant must be added to the system through the
suction side of the compressor, charge in vapor form only. Liquid charging must be done in the high side only or with
liquid metering devices to protect the compressor.
Low Head Pressure Systems
If you are charging the system by using a clear sight glass as an indication of proper charge the following must be considered.
Check the condensing temperature. It must be above 105˚F. If not, it will be necessary to reduce the amount of air going through the condenser from fans still running. Simply reduce the effective condenser face area to raise the discharge pressure above the equivalent 105˚F condensing temperature and then proceed to charge to clear the sightglass. Adjust evaporator superheat at this time. Return to full condenser face area and allow the system to balance.
Field Wiring
WARNING:
All wiring must be done in accordance with applicable codes and local ordinances.
The field wiring should enter the areas as provided on the unit. The wiring diagram for each unit is located on the inside of the electrical panel door. All field wiring should be done in a professional manner and in accordance with all governing codes. Before operating unit, double check all wiring connections, including the factory terminals. Factory connections can vibrate loose during shipment.
1.The serial data tag on the unit is marked with the electrical characteristic for wiring the unit.
2.Consult the wiring diagram in the unit cooler and in the condensing unit for proper connections.
3.Wire type should be of copper conductor only and of the proper size to handle the connected load.
4.The unit must be grounded.
5.For multiple evaporator systems, the defrost termination controls should be wired in series. Follow the wiring diagrams for multiple evaporator systems carefully. This will assure complete defrost of all evaporators in the system.
6.Multiple evaporator systems should operate off of one thermostat.
7.If a remote defrost timer is to be used, the timer should be located outside the refrigerated space.
8.For air cooled condensers, due to multiple low amp motors, we recommend using time delay fuse protection instead
of circuit breakers.
