JOHNSON CONTROLS
74
FORM 100.50-NOM12
ISSUE DATE: 04/02/2019
SECTION 5 – SEQUENCE OF OPERATION
TABLE 27 - COMPRESSOR STAGING
STAGES STAGING ON
0 to 1 When both compressors 1A and 1B are ready to run, the IPU board turns ON the compressor with the fewest starts
1 to 2
When compressors 2A, 2B, 3A, and 3B are ready to run, the IPU board turns ON the compressor with the
fewest starts
2 to 3
The IPU board turns ON either the A or B compressor with the fewest starts from the remaining circuit that is
not yet active
3 to 4 The IPU board turns ON the inactive compressor from the circuit started in the stage 0 to 1 step
4 to 5 The IPU board turns ON the inactive compressor from the circuit started in the stage 1 to 2 step
5 to 6 The IPU board turns ON the inactive compressor from the circuit started in the stage 2 to 3 step
STAGES STAGING OFF
6 to 5
When compressors 3A, 3B, 2A, and 2B are all ready to stop, the IPU board turns OFF the compressor with the
fewest starts
5 to 4
Whichever circuit 2 or 3 still has two compressors operating, the IPU board turns OFF the compressor with the
fewest starts
4 to 3 Turn OFF compressor 1A or 1B, whichever has the fewest starts
3 to 2 Turn OFF a compressor from either circuit 2 or 3 that has the fewest starts
2 to 1 Turn OFF the last active compressor from either circuit 2 or 3
1 to 0 Turn OFF the active compressor from circuit 1
Fast Compressor Start
• The Series 100 unit's patented Fast Compressor Start
sequence stages ON compressors quickly when
switching from a Standby mode to a Cooling mode.
• Fast compressor start can be User Enabled/User
Disabled. It can be found under the PROGRAM-
UNIT DATA menu.
Fast Compressor Start is User Enabled
1. When the IPU board switches from a Standby
mode to a Cooling mode, it uses internal program-
ming logic to determine the correct stage of cool-
ing that is needed.
2. Once the correct stage is determined, the IPU board
stages ON compressors, with a 15 second time de-
lay in between, until the appropriate numbers of
compressors are operating.
3. Once the appropriate stage is reached, normal
compressor staging applies, with a 3.5 minute
time delay between compressor starts/stops.
4. One of the variables used in fast compressor start
is the unit design airow. This value needs to be
entered correctly for fast compressor start to work
properly. Unit design airow can be found in the
SETPOINTS-UNIT DATA menu.
Fast Compressor Start is User Disabled
• When the IPU board switches from a Standby
mode to a Cooling mode, it stages ON compres-
sors one at a time with the normal 3.5 minute time
delay between staging on a new compressor.
Compressor Operation
• The Series 100 units utilize scroll compressor
technology.
• The IPU board constantly monitors the compres-
sor safety circuit, LPCO switch, and suction line
temperature of a compressor circuit.
• The mechanical cooling lockout setpoint is
50.0°F. No compressor operation is allowed be-
low this temperature unless a low ambient pack-
age was ordered. Low ambient packages can be
ordered for one, two, or three systems.
• Each compressor circuit has a tandem set of com-
pressors piped together to a common suction and
discharge line. There is an oil equalization line be-
tween the two compressors.
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