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Operation
The Value setting is the factory default setting on
Sensors used for this delta T are: room/local sensor or the return air sensor; and the glycol sensor. If this delta T is true, the following actions will be performed:
1.The
2.The compressor band will be shifted to the right by 100%, and within the first 100% the free- cooling valve band will take place (see Figure 18).
Figure 18 Second cooling source and compressorized cooling
Temp Setpoint: 70°F
Proportional Band: 8°F
Deadband: 2°F
Valve | Valve 100% | Cool 1 | Cool 2 |
Closed | Open | On | On |
| + 100% |
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½ Dead- | Cooling |
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band
2ndComp Source
70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 |
0% Cooling
½ Proportional Band | ½ Proportional Band | + 200% | |
Band1: 2nd Source | Band 2: Compressors | ||
Cooling |
Increasing Temperature
Minimum Chilled Water
Below this minimum chilled water setpoint, parameter Minimum CW Temp Value, (Service Menu, Setpoints), the control will operate ONLY the second cooling source control, i.e., the compressor is locked out. Above the minimum chilled water setpoint, assuming the fluid temperature is below the return room air temperature (delta T between room and glycol = true), the control will operate the second cooling source control and compressor control simultaneously if needed.
If the Minimum CW Temp is disabled, the second cooling source temperature is ignored, the control will always operate the second cooling source and compressors simultaneously when the load requires it.
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