displayed informing the operator that the chiller is operating in ramp loading mode.
l.Chilled Water Reset:
The control center shall allow reset of the chilled water temperature set point based on any one of the following criteria:
1)Chilled water reset based on an external 4 to 20 mA signal.
2)Chilled water reset based on a remote temperature sensor (such as outdoor air).
3)Chilled water reset based on water tem- perature rise across the evaporator.
m.Demand Limit:
The control center shall limit amp draw of the compressor to the rated load amps or to a lower value based on one of the following criteria:
1)Demand limit based on a user input ranging from 40% to 100% of compres- sor rated load amps
2)Demand limit based on external 4 to 20 mA signal.
n.Controlled Compressor Shutdown:
The controls shall be capable of being configured to soft stop the compressor. The display shall indicate “shutdown in progress.”
2.Safeties:
a.Unit shall automatically shut down when any of the following conditions occur (each of these protective limits shall require manual reset and cause an alarm message to be dis- played on the control panel screen, inform- ing the operator of the shutdown cause):
1)Motor overcurrent
2)Over voltage*
3)Under voltage*
4)Single cycle dropout*
5)Low oil sump temperature
6)Low evaporator refrigerant temperature
7)High condenser pressure
8)High motor temperature
9)High compressor discharge temperature
10)Low oil pressure
11)Prolonged stall
12)Loss of cooler water flow
13)Loss of condenser water flow
14)Variable frequency drive fault
15)High variable frequency drive temperature
*Shall not require manual reset or cause an alarm if
b.The control system shall detect conditions that approach protective limits and take self- corrective action prior to an alarm occur- ring. The system shall automatically reduce chiller capacity when any of the following
parameters are outside their normal operat- ing range:
1)High condenser pressure
2)High motor temperature
3)Low evaporator refrigerant temperature
4)High motor amps
5)High VFD rectifier temperature
6)High VFD inverter temperature
c.During the capacity override period, a pre- alarm (alert) message shall be displayed informing the operator which condition is causing the capacity override. Once the con- dition is again within acceptable limits, the override condition shall be terminated and the chiller shall revert to normal chilled water control. If during either condition the protective limit is reached, the chiller shall shut down and a message shall be displayed informing the operator which condition caused the shutdown and alarm.
d.Internal built in safeties shall protect the chiller from loss of water flow. Differential pressure switches shall not be allowed to be the only form of freeze protection.
3.Diagnostics and Service:
a.A self diagnostic controls test shall be an integral part of the control system to allow quick identification of malfunctioning components.
b.Once the controls test has been initiated, all pressure and temperature sensors shall be checked to ensure they are within normal operating range. A pump test shall automat- ically energize the chilled water pump, con- denser water pump, and oil pump. The control system shall confirm that water flow and oil pressure have been established and require operator confirmation before pro- ceeding to the next test.
c.In addition to the automated controls test, the controls shall provide a manual test which permits selection and testing of indi- vidual control components and inputs. A thermistor test and transducer test shall dis- play on the ICVC screen the actual reading of each transducer and each thermistor installed on the chiller. All
4.Multiple Chiller Control:
The chiller controls shall be supplied as stan- dard with a
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