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Reverse Rotation Board —
board monitors the three-phase electrical system to provide
phase reversal, phase loss and under-voltage protection. See
Fig. 8. In addition, a 24-v time delay relay and contactor is used
to deenergize the entire control power of the chiller as part of
the protection scheme. See Fig. 9. The reverse rotation board
has two LEDs (light-emitting diodes) and two adjustable dial
settings. Under normal conditions, the upper LED will light up
green. The lower LED is red and will flash (phase reversal) or
turn on solid (phase loss and under-voltage) according to the
conditions sensed.
DIAL SETTINGS — The reverse rotation board has two di-
als. See Fig. 8. The upper dial should be set to match the in-
coming three-phase voltage to the chiller with no compressors
running. This dial must be adjusted for 208/230-v chillers oper-
ating on 208-v power supply. The dial should be adjusted to
200-v minimum setting for this case. The lower dial is used for
trip delay and should be set fully counterclockwise to the mini-
mum 0.1 second setting. The time delay relay in the 24-v cir-
cuit has a delay setting as well and it should be set fully clock-
wise to the maximum 1.0 second setting. See Fig. 9.
PHASE REVERSAL PROTECTION — The control moni-
tors the three-phase power sequence supplied at terminals L1,
L2, and L3. If the control senses an incorrect phase relation-
ship, the relay contacts (11/14) on the board will open. The re-
lay contacts will automatically reset when the correct phase se-
quence is applied.
PHASE LOSS AND UNDER-VOLTAGE PROTEC-
TION — If the reverse rotation board senses that any one of
the three phase inputs has no AC voltage or that any one phase
has dropped more than 20% below the voltage dial setting, the
relay contacts (11/14) on the board will open. In addition,
board relay contacts (21/24) will also open. If the contacts do
not close within one second (time delay relay dial setting), the
24-v control power to the chiller will be removed and all motor
outputs will be turned off. Control power will be restored auto-
matically when all three phases are present, in the correct se-
quence and are within the limits of the voltage dial setting.
LED STATUS
Upper (green) LED on
continuously
Lower (red) LED blinking
Lower (red) LED on
continuously
Upper (green) LED off
NOTE: Normal operation of the reverse rotation board (for
example, no faults are detected) results in a closed contact
being applied to the MBB (plug J5A, channel 16B) through the
closed 11/14 relay contact.
Enable-Off-Remote Contact Switch —
is installed in all units and provides the owner and service
person with a local means of enabling or disabling the
machine. It is a 3-position switch used to control the chiller.
When switched to the Enable position the chiller is under its
own control. Move the switch to the Off position to shut the
chiller down. Move the switch to the Remote Contact position
and a field-installed dry contact can be used to start the chiller.
The contacts must be capable of handling a 24-vac, 20-mA
load. In the Enable and Remote Contact (dry contacts closed)
positions, the chiller is allowed to operate and respond to the
scheduling configuration, CCN configuration and set point
control.
Emergency On/Off Switch —
in all units. The Emergency On/Off switch should only be used
The reverse rotation
FUNCTION
Relay contacts closed (normal
operation)
Relay contacts open (phase rever-
sal has occurred)
Relay contacts open (phase loss
or under-voltage has occurred)
Power not present at L1, L2, L3
(off)
This switch
This switch is installed
when it is required to shut the chiller off immediately. Power
to the MBB, energy management module, and scrolling
marquee display is interrupted when this switch is off and all
outputs from these modules will be turned off.
Fig. 8 — Reverse Rotation Board (RRB)
Fig. 9 — Time Delay Relay
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