(Pump 1 Starts First) or 2 (Pump 2 Starts First). If PM.SL is 0 (Automatic), the pump selection is based on two criteria: the alert status of a pump and the operational hours on the pump. If a pump has an active Alert condition, it will not be considered for the lead pump. The pump with the lowest operational hours will be the lead pump. A pump is selected by the control to start and continues to be the lead pump until the Pump Changeover Hours (Configuration→OPT1→PM.DT) is reached. The Lead Pump (Run Status→VIEW→LD.PM) indicates the pump that has been selected as the lead pump: 1 (Pump 1), 2 (Pump 2), 3 (No Pump). The Pump Changeover Hours is facto- ry defaulted to 500 hours. Regardless of the Cooler Pump Se- lection, any pump that has an active alert will not be allowed to start.
With the dual integral pump package, the Cooler Pump Starter will be energized when the machine is in an occupied period. As part of the
If Pump 2 starts and the auxiliary contact interlock does not close within 25 seconds of the ON command, a T191 — Cooler Pump 2 Aux Contacts Failed to Close at
—Cooler Pump 2 Failed to Provide Flow at
If the chilled water flow switch opens for at least 3 seconds after initially being closed, a T196 — Flow Lost While Pump 1 Running Alert or T197 — Flow Lost While Pump 2 Running Alert for the appropriate pump and an A201 — Cooler Flow/ Interlock Contacts Opened During Normal Operation Alarm will be generated and the machine will stop. If available, the other pump will be started. If flow is proven, the machine will be allowed to restart.
If the chilled water pump interlock opens for 25 seconds after initially being closed is detected by the control, the appro- priate T194 — Cooler Pump 1 Contacts Opened During Nor- mal Operation Alert or T195 — Cooler Pump 2 Contacts Opened During Normal Operation Alert is generated and the unit is shut down. If available, the other pump will be started. If flow is proven, the machine will be allowed to restart.
If the control detects that the chilled water flow switch circuit is closed for at least 5 minutes with the pump output OFF, an A202 — Cooler Pump Interlock Closed When Pump is Off Alarm will be generated and the unit will not be allowed to start.
If the control detects that the chilled water pump auxiliary contacts are closed for at least 25 seconds while the pump is OFF, the appropriate T198 — Cooler Pump 1 Aux Contacts Closed While Pump Off or Alert T199 — Cooler Pump 2 Aux Contacts Closed While Pump Off Alert is generated. The chiller will not be allowed to start.
If the control starts a pump and the wrong interlock circuit closes for at least 20 seconds, an A189 – Cooler Pump and Aux Contact Input Miswire Alarm will be generated. The unit will be prevented from starting.
The control will allow for pump changeover. Two methods will change the pump sequence. Before the changeover can occur, the unit must be at Capacity Stage 0. During changeover the chilled water flow switch input is ignored for 10 seconds to avoid a nuisance alarm.
With Cooler Pump Select (Configuration→OPT1→ PM.SL) set to 0 (Automatic) and when the differential time limit Pump Changeover Hours (Configuration→OPT1 →PM.DT) is reached, the lead pump will be turned OFF. Ap- proximately one (1) second later, the lag pump will start. Manu- al changeover can be accomplished by changing Rotate Cooler Pump Now (Configuration→OPT1→ROT.P) to YES only if the machine is at Capacity Stage 0 and the differential time limit Pump Changeover Hours (PM.DT) is reached. If the PM.DT is not satisfied, the changeover will not occur. With the machine at Capacity Stage 0, the pumps would rotate automatically as part of the normal routine.
With Cooler Pump Select (PM.SL) set to 1 (Pump 1 Starts First) or 2 (Pump 2 Starts First), a manual changeover can be ac- complished by changing PM.SL only. The machine Remote-
As part of a pump maintenance routine, the pumps can be started to maintain lubrication to the pump seal. To utilize this function, Cooler Pmp Periodic Start (Configuration→OPT1 →PM.PS) must be set to YES. This option is set to NO as the factory default. If feature is enabled and the pump(s) are not operating, then the pumps will be operated every other day for 2 seconds starting at 14:00 hours. If a pump has failed and has an active Alert condition, it will not be started that day.
Configuring and Operating Dual Chiller Con-
trol — The dual chiller routine is available for the control of two units supplying chilled fluid on a common loop. This control algorithm is designed for parallel fluid flow arrangement only. One chiller must be configured as the master chiller, the other as the slave. An additional leaving fluid temperature thermistor (Dual Chiller LWT) must be installed as shown in Fig. 16 and 17 and connected to the master chiller. Refer to Sen- sors section, page 20, for wiring. The CCN communication bus must be connected between the two chillers. Connections can be made to the CCN screw terminals on LVT. Refer to Carrier Comfort Network® Interface section, page 19, for wiring infor- mation. Configuration examples are shown in Tables 22 and 23.
Refer to Table 22 for dual chiller configuration. In this example the master chiller will be configured at address 1 and the slave chiller at address 2. The master and slave chillers must reside on the same CCN bus (Configuration→CCN →CCNB) but cannot have the same CCN address (Configu- ration→CCN→CCNA). Both master and slave chillers must have Lead/Lag Chiller Enable (Configuration→RSET →LLEN) configured to ENBL. Master/Slave Select (Config- uration→RSET →MSSL) must be configured to MAST for the master chiller and SLVE for the slave. Also in this example, the master chiller will be configured to use Lead/Lag Balance Select (Configuration→RSET→LLBL) and Lead/Lag Bal- ance Delta (Configuration→RSET→LLBD) to even out the chiller
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