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© 2015 Heatcraft Refrigeration Products, LLC
Figure 4. Pad Mount for Mobile or Deep Sump Application
Condensing Unit Rigging and Mounting
Rigging holes are provided on all units. Caution should be exercised when moving
these units. To prevent damage to the unit housing during rigging, cables or chains
used must be held apart by spacer bars. The mounting platform or base should be
level and located so as to permit free access of supply air.
Ground Mounting
Concrete slab raised six inches above ground level provides a suitable base. Raising
the base above ground level provides some protection from ground water and wind
blown matter. Before tightening mounting bolts, recheck level of unit. The unit should
in all cases be located with a clear space in all directions that is at a minimum, equal
to the height of the unit above the mounting surface. A condensing unit mounted in
a corner formed by two walls, may result in discharge air recirculation with resulting
loss of capacity.
Roof Mounting
Due to the weight of the units, a structural analysis by a qualified engineer may be
required before mounting. Roof mounted units should be installed level on steel
channels or an I-beam frame capable of supporting the weight of the unit. Vibration
absorbing pads or springs should be installed between the condensing unit legs or
frame and the roof mounting assembly.
Access
Sufficient access must provided to ensure future service of all major components is pos-
sible. The screw compressor, as well as some of the compressors removable components
are heavy enough to require additional lifting equipment for service. Care must be taken
during condensing unit placement to accommodate the use of service equipment for
maintenance or repair.
Pad Mounted Compressor
All units use pad mounted compressors. Check the compressor mounting bolts to
insure they have not vibrated loose during shipment. See Figure 4.
Head Pressure Control
Head pressure control is managed by the microprocessor controller. Fan manage-
ment is constantly monitored and adjusted by the controller to maintain the target
head pressure.
a. Dual Valve System
The system employs an ORI (open on rise of inlet pressure) valve and an ORD
(open on rise of differential pressure) valve. The high pressure discharge gas is
introduced above the liquid in the receiver tank. The receiver discharge is regulated
by the ORI valve.
Operation and Adjustment
Condensing units with dual valves require sufficient charge to partially flood the
condenser during low ambient conditions.
Valve adjustment should be made with gauges connected to the discharge port of
the compressor. Adjustments should be made during mild or low ambient conditions.
Turning the valve stem “clockwise” on the ORI valve will increase the discharge
pressure, while turning the valve stem “counterclockwise” will decrease the discharge
pressure.
If adjustments are made during warm ambient conditions, it may not be possible to
adjust the regulator valve as low as desired. Readjustment may be necessary once
cooler conditions prevail.
The discharge pressure of the ORI valve must be adjusted to regulate the unit for
proper operating conditions. Adjust the ORI valve shown on the following diagram to
maintain a discharge pressure of 160 to 180 PSIG.“flooding” of the condenser with
liquid refrigerant reduces the available condensing surface, holding the condensing
pressure at the valve setting.
b. Ambient Fan Cycle Control
This is an automatic winter control method which will maintain a condensing pressure
within reasonable limits by cycling fan motors in response to outside air temperature.
The thermostat(s) should be field adjusted to shut off the fan when the condensing
temperature is reduced to approximately 90
˚
F. Table 1 lists approximate settings for
several system T.D.’s. These settings are approximate as they do not take into account
variations in load.
Rubber
Oil Type
BITZER Compact Screws are available in both standard CSH models for medium and
high temperature condensing applications. These compressors offer excellent part and
full load efficiencies.
A key aspect to utilizing these compressors to their fullest potential is specifying
the correct oil for your refrigerant. CSH screws may use BSE 170 oil in a variety of
refrigerants (R134a, R407C, R404A and R507A).
Table 2. Refrigeration Oils
ISO 170 (880 SUS) POE oil
OIL CHANGE
As received, the POE lubricant will be clear or straw colored. After use, it may acquire
a darker color. This does not indicate a problem as the darker color merely reflects the
activity of the lubricant's protective additive.
BYPASS
REGULATOR
CHECK
VALVE
DRAIN
REGULATOR
STD. LIQUID
LINE OUTLET
RECEIVER
DIP TUBE
COMPRESSOR
AIR COOLED
CONDENSER
DISCHARGE
LINE
Washer
Compressor for
Mounting Foot