Manual 2100-694B
Page
25 of 62
6. If an offset needs to be applied, press ENTER key
to scroll to
Offset
.
7. Press UP or DOWN keys to change the offset to
desired value.
8. Press ENTER key to save.
9. Press ESCAPE key several times to return to Main
Menu screen.
Condenser Fan Operation
Condenser Fan Speed Control
Mechanical Cooling
This unit controls condenser fan speed based on unit
liquid line pressure. The condenser fan speed will
generally operate to a nominal liquid line pressure
setpoint, but can increase the setpoint for high ambient
scenarios or decrease it for low ambient scenarios.
Because the control is dependent on the liquid line
pressure sensor, the controller will alter its operation if
the sensor is not enabled or failed. When the liquid line
pressure transducer is not enabled or considered failed
by the controller, a nominal fan speed will be used
during a compressor call.
NOTE:
If the outdoor temperature sensor or liquid
line pressure sensor is disabled or fails, the
condenser fan speed will be set to the nominal
operating speed.
High Pressure Control
Condenser Fan Speed
In certain conditions, like when outdoor temperatures rise
past nominal condensing temperatures, high side system
pressures will increase. When this happens, the liquid
line setpoint for the condenser fan will shift to allow the
system to build more heat that can be transferred in the
condenser, and the fan will operate at higher speeds to
remove as much heat as it effectively can.
Second Stage Drop Out
If the liquid pressure reaches 620 PSI, the second
stage of cooling will be disabled for the remainder of
the cooling call. Second stage compressor operation
will resume on next call for compressor.
Low Ambient Control
At low ambient outdoor air temperatures, the fan motor
will cycle as a means of controlling the system's head
pressure to protect the system from evaporator coil
freeze conditions. The process for this system is as
follows: If the liquid pressure falls below 250 PSI, the
condenser fan will turn off. The fan will remain off
while the compressor remains running, allowing the
head pressure to build up. Once the liquid pressure
reaches 350 PSI, the fan will then turn back on at
the appropriate speed. At lower ambient outdoor
temperatures, this may cycle regularly as normal
operation. In some cases, in higher wind prone areas,
the condenser fan may stay off for prolonged durations
due to low liquid pressures.
Compressor
Compressor Components
Compressor
Three Phase Scroll Compressor Start Up Information
Scroll compressors, like several other types of
compressors, will only compress in one rotational
direction. Direction of rotation is not an issue with
single phase compressors since they will always start
and run in the proper direction.
However, three phase compressors will rotate in either
direction depending upon phasing of the power.
Since there is a 50-50 chance of connecting power
in such a way as to cause rotation in the reverse
direction, verification of proper rotation must be made.
Verification of proper rotation direction is made by
observing that suction pressure drops and discharge
pressure rises when the compressor is energized.
Reverse rotation also results in an elevated sound level
over that with correct rotation, as well as substantially
reduced current draw compared to tabulated values.
Verification of
proper rotation
must be made at the time
the equipment is put into service. If improper rotation
is corrected at this time, there will be no negative
impact on the durability of the compressor. However,
reverse operation for over 1 hour may have a negative
impact on the bearing due to oil pump out.
NOTE:
If compressor is allowed to run in reverse
rotation for an extended period of time, the
compressor’s internal protector will trip.
All three phase compressors are wired identically
internally. As a result, once the correct phasing is
determined for a specific system or installation,
connecting properly phased power leads to the same
Fusite terminal should maintain proper rotation direction.
The direction of rotation of the compressor may be
changed by reversing any two line connections to the
wall-mount unit.
Compressor Control Module (CCM)
Delay-on-Make Timer
Short Cycle Protection/Delay-on-Break
Test Mode
High Pressure Detection
Brownout Protection with Adjustment
The LPC terminals are jumpered in this application.
Instead, the low pressure transducer is used for low
pressure monitoring.
Delay-on-Make Timer
In the event of power loss, a delay-on-make timer is
included to be able to delay startup of the compressor.
This is desired when more than one unit is on a
