Condensing Unit Operational Control; Control Features; Fresh Start Program; Stop Program - Emerson Copeland Scroll Installation And Reference Manual

wall (or the next unit) be maintained from the unit's left
and rear panel whereas a clearance of 20 inches is to
be maintained from the unit's right, top and front panels.
Both service access and airfl ow have been considered
in making these recommendations. Where multiple
units are to be installed in the same location, careful
consideration for proper clearance needs to be given
to each individual unit.
Ideally, the unit should be mounted level on a solid
concrete slab with rubber strips between unit feet and
concrete. However, these units have been designed for
mounting on suitable brackets for wall mounting. In this
case it is equally important that the spatial guidelines
given above are followed, and additional consideration
needs to be given for possible air recycling if units are
stacked above and below each other. In general terms,
air by-pass around each condenser and between each
unit should be avoided at all times.
Pipe sizing should not only be of suffi cient size to ensure
optimum performance and good oil return, but it also
needs to take into account the full capacity range through
which this particular unit will need to operate. Follow the
ASHRAE guidelines for proper piping practices.

Condensing Unit Operational Control

The Digital Control electronic control board controls the
operation of the condensing unit. Whenever there is a
control input asking to start or stop the condensing unit,
the control board will execute a set of pre-programmed
procedures to do so. It also monitors the compressor
operating parameters, so as to protect the system from
unsafe operating parameters. See Figure 3 (page 8).
For example, when the low temperature unit experiences
an extreme temperature day, the control board decides
to switch from vapor-injection-optimization to discharge
gas temperature control to allow the compressor to run
safely and pass the extreme weather hours.

Control Features

The base control function is for the following standard
features. See Figure 3 for additional input options and
output options of the control board.

Fresh Start Program

This Fresh Start Program is a bump start procedure that
will energize and start the compressor for 3 seconds
and then will be followed by a 20 second off cycle time.
This will occur for 3 cycles, and then continuous power
will be supplied to the compressor for normal operation.
The Fresh Start Program will be executed on initial start
up or any time power is reapplied when the ambient
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Application Engineering
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temperature is lower than 95°F. In addition, the Fresh
Start Program will be executed for any start when the
unit has been cycled off for more than an hour when the
ambient temperature is lower than 95°F.

Stop Program

When the unit is satisfi ed, or there is any error which
requires the unit to be shut down, the controller will
execute a Stop Program. The compressor and the
condenser fans will cycle off and the injection valves
will close.
For low temperature units only, when the unit is
satisfi ed the EXV will start closing immediately, but the
compressor will delay 5 seconds before shut down to
prevent reverse rotation of the compressor.
Automatic Liquid Injection (Medium temperature
units only)
Automatic Liquid Injection ensures that the scroll
compressor operates within a safe temperature limit.
This unit employs a patented liquid injection system
which injects a saturated refrigerant into the suction
line at the compressor. Activation of the liquid injection
valve is in response to a thermistor which is attached
to the compressor discharge line. A signal is sent to the
stepper motor of the injection valve, opening the valve
in response to increasing discharge temperatures and
injecting saturated refrigerant to reduce the discharge
temperature.

Compressor Phase Reversal

Compressor Phase Reversal senses for the correct
phase sequence on three phase applications. Reset is
automatic once the correct phase sequence is sensed.
An error message will be shown on the diagnostic LED.

Loss of Phase Protection

If three phase supply is incorrectly connected to the
contactor terminals, or if a missing phase is sensed, an
error message will be shown on the diagnostic LED.
Reset is automatic once the correct phasing is sensed.
Motor Current Overload
•
All scroll compressors used in these condensing
units have an internal inherit motor protector.
•
The Copeland Scroll Outdoor Condensing Unit is
also equipped with two current sensors (CT1, CT2)
to monitor the electrical current of the condensing
unit. If the condensing unit current exceeds a pre-
defi ned current limit, the controller will take the
following actions:
□
Stop the compressor for 3 minutes
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