Parallel Compressor Systems
Ventilation Requirements
Indoor Units
If compressors or condensing units are located in a machine room, adequate ventilation air must be provided to avoid an excessive temperature rise in the room. To allow for peak summer temperatures a 10°F temperature rise is recommended, although a 15°F rise might be acceptable.
With compressors with remote condensers, approximately 10% of the heat rejected is given off by the compressor casting and the discharge tubing. The correct formula for calculating the ventilation requirement of the Indoor Parallel unit is:
CFM = 10% of THR / hr
10° TD
The air intake should be positioned so that air passes over the units. All State, Local, and National codes should be followed.
Electrical
To insure the proper operation of equipment and reduce the possibility of interruption of refrigeration due to electrical power failure, the following precautions must be observed:
•All electrical work must be done in accordance with the National Electrical Code and existing local codes
•The power supply must be the same as specified on the unit data plate
•An adequate power supply must be provided
•Voltage fluctuations in excess of 10 percent must be corrected
•Overload relays (Carrier compressors only) are selected in accordance with specified limits as determined by the
•Control panels must be provided with a single phase, 60 Hertz supply. See the unit wiring diagram for the voltage requirement
•Before starting up a parallel unit, insure that all fuses and
Refrigerant Piping
The system as supplied by Heatcraft, was thoroughly cleaned and dehydrated at the factory. Foreign matter may enter the system by way of the field piping required. Therefore, care must be used during installation of the piping to prevent introduction of foreign matter.
Install all refrigeration system components in accordance with all applicable local and national codes and in conformance with good practice required for the proper operation of the system.
Proper size refrigeration lines are essential to good refrigeration performance. Suction lines are more critical than liquid or
discharge lines. Oversized suction lines may prevent proper oil return to the compressor. Undersized lines can rob refrigeration capacity and increase operating cost. Consult the line sizing charts in this manual for proper pipe sizes.
The following procedures should be followed:
1.Do not leave dehydrated compressors or
2.Use only refrigeration grade copper tubing, properly sealed against contamination
3.Suction lines should slope 1/4” per 10 feet towards the compressor
4.Discharge lines should slope 1/4” per 20 feet toward the condenser
Suction P-Traps
•Provide
Figure 4. P-Trap Requirements
*The
Figure 5. P-Trap Construction
Parallel Compressor Systems Installation & Operations Manual, October 2004 | 7 |
