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7
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 motor-compressor
manufacturer. They must not be changed in
size or shorted-out.
• 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 motor-protective devices are in
place and that all wiring is secure. A
complete wiring diagram for troubleshooting
the unit will be found inside the control panel
cover.
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
filter-driers open to the atmosphere.
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 P-traps at the base of each suction
riser of four (4) feet or more to enhance oil
return to the compressor. Use a P-trap for
each 20 feet section of riser. See Figure 4
below.
Figure 4. P-trap Requirements
* The P-trap should be the same size as the
horizontal line. See Figure 5 below.
Figure 5. P-Trap Construction