Binary Outputs-Auxiliary Control Boards (Ccb1 And Ccb2); Ccb1 & Ccb2; Compressors-2 Stages - McQuay MicroTech II Installation And Maintenance Manual

Binary Outputs—Auxiliary Control Boards
(CCB1 and CCB2)
The optional auxiliary control boards include 9 binary
outputs that control 9 on-board electromechanical relays.
Unit control devices are wired to these outputs through
output terminals on the left side of the board. The functions
of these outputs vary for the different auxiliary board
applications. The following sections describe the output
functions for the auxiliary control board applications.
CCB1 & CCB2
Circuit #1 through Circuit #4 are controlled by the CCB1
and Circuit #5 and #6 are controlled by the CCB2. There are
nine binary output relays on each cooling control board.
These relays are energized based on commands received
from the MCB to provide the appropriate switching actions
in the DX cooling control circuits.
There are a number of different compressor/stage
configurations available on these units. The following
sections describe the DX staging sequencing for each
configuration.
Table 15: Binary outputs for cooling control boards (CCB1 and CCB2)
Cooling Circuit # Output #
BO1
BO2
BO3
BO4
1
BO5
(CCB1)
BO6
BO7
BO8
BO9
BO1
BO2
BO3
BO4
2
BO5
(CCB2)
BO6
BO7
BO8
BO9
22
Compressor #1 On/Off
Compressor #2 On/Off
Pump Start
Not Used
Not Used
Compressor #3 On/Off
Not Used
Not Used
Compressor #4 On/Off
Compressor #5 On/Off
Compressor #6 On/Off
Pump Start
Not Used
Not Used
Not Used
Not Used
Not Used
Not Used
2 Compressors—2 Stages
There are two equally sized compressors and two
independent cooling circuits. The unit capacity is increased
or decreased by turning compressors on and off. One of the
compressors is designated the "Lead" and the other "Lag."
Based on operating hours. The compressor with the fewest
run hours is staged on first and turned off last. When a
capacity increase is required and the cooling capacity is 0%,
the "Lead" compressor is staged on. When further capacity
is required, the "Lag" compressor is staged on. Disabled
compressors are not turned on.
For detailed information regarding compressor lead/lag
operation, refer to the "Compressor Staging" section of the
applicable operation manual (refer to Table 1 on page 1).
Table 14 summarizes the staging sequencing for the
2-Compressor—2-Stage cooling configuration.
Table 14: 2 compressors—2 stages
Stages
1
2
Description
Compressors
1 or 2
1,2
Action With Output On
On
On
On
-
-
On
-
-
On
On
On
On
-
-
-
-
-
-
McQuay IM 710-1