User manual

Teamwork
77 Liebert
®
iCOM
®
4.2.2 No Teamwork
All cooling units work independently, responding to their own sensors. Standby function and unit
rotation are possible, but cascading is not (see Standby and Cascade on page 90). Autoset will not
adjust the proportional band in this mode.
4.2.3 Teamwork Mode 1
Teamwork Mode 1 works best in small rooms with balanced heat loads. The return temperature and
humidity sensor readings of all units in operation (fan on) are averaged by the master unit, Unit #1,
and used for control. The master unit will send the operating requirements to all operating units
according to unit numbers, rotated by one unit every 24 hours.
In this teamwork mode, most of the parameters are shared; if set in any one of the units, all other
units will follow with the same settings. AutoSet will adjust the proportional band in Teamwork
Mode 1, see 3.2.1 - Temperature Proportional Band.
The master unit evenly divides the system proportional band among the number of available units.
Each unit will receive instruction on how to operate from the master unit based on how far the system
deviates from the setpoints.
The number of available units is calculated like:
• In non-standby configuration: all units with fan on
• In typical standby function (no cascade): all units with fan on
• In cascade mode: all units that could operate (no alarm, which forces the unit to switch Off, unit
not switched Off, etc.)
Figure 64 shows how two cooling units work together in Teamwork Mode 1,staging compressors
serially. Since Unit 1 and Unit 2 are available to operate, the master unit, Unit 1, collects the average
or maximum (based on S804 “Teamwork is based on” programming) temperature and humidity
sensor readings from each unit. Settings in S804 “Teamwork is based on” programming determines
whether the unit uses the average or maximum temperature and humidity sensor.
The master unit determines that a 60% call for cooling is required for the system. Since there are two
available cooling units, each unit makes up half of the system proportional band; Unit 1 handles
0-50% system call for cooling and Unit 2 handles 51-100%. For every 1% system call for cooling, each
unit provides 2% of its total cooling capacity.
The 60% system call for cooling exceeds the 50% Unit 1 can provide, so Unit 1 operates at full
capacity. The remaining 10% system call for cooling (60% - 50% = 10%) is handled by Unit 2. Unit 2
responds by operating at 20% cooling capacity (50% - 10% = 40%).
NOTE
1. Proportional actuators (chilled water valves and free-cooling valves) are driven in parallel.
2. Dual-cool and free-cooling units cannot be set in Teamwork 1 if compressors and
free-cooling valves are set for simultaneous operation.
3. On free-cooling or dual-cool units where simultaneous operation is set to No, chilled water
valves ramp in parallel. If free-cooling is not possible for one unit, the group will switch to
compressor operation. Compressor staging may work serially or in parallel depending on
compressor type. See below for compressor ramping.
• The compressors will ramp in parallel if all units in the group are digital scroll.
• Compressor staging will be done serially if all the units in the group are four-step, two-
step semi-hermetic or standard scroll.
• Compressor staging will be done in parallel if there is a mix of digital scroll compressors
with four-step, two-step semi-hermetic or standard scroll.
4. Low limit and dehumidification are managed from each unit independently.