Teamwork
The number of available units is calculated like:
•In
•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.)
NOTE
1. Proportional actuators (chilled water valve,
2.Changeover to second cooling source, low limit during dehumidification and low supply limit control air local functions, managed from each unit independently.
Figure 23 shows how two cooling units work together in Teamwork Mode 1. Since Unit 1 and Unit 2 are available to operate, the master unit, Unit 1, averages the temperature and humidity sensor read- ings from each unit.
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 capac- ity. 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% = 20%).
Figure 23 Teamwork Mode 1 with two cooling units
System Deviation : 60%
System |
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Proportional |
| Heating | Cooling | |
Band |
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- Temp | ½ Proportional Band | ½ Proportional Band | + | |
| Temp | |||
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| - 100% | 0% | + 100% | |
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| Setpoint |
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| Unit1 Deviation: 100% |
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| Unit2 Deviation: 20% |
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Individual |
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| Cooling |
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| Cooling |
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Units |
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| + Temp |
| + Temp | ||
| 0% | ½ Proportional Band | ½ Proportional Band | ||||
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| 0% |
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| + 100% | + 100% | ||||
| Setpoint | ||||||
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| Setpoint |
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40