Emerson ENV10G, ENV20G, 1.5 TO 10 TONS, 60HZ user manual Sequence of Operation, Time delay settings

Sequence of Operation

2.0SEQUENCE OF OPERATION

During normal operation, cold fluid flow from the chiller passes across the flow switch, through the heat exchanger, through the pump bypass check valve, past the supply temperature sensor and out to the load (see Figures 1 and 2). The standby cooling solenoid valve is closed (de-energized) and the standby pump is off.

If the flow switch senses loss of flow, a time delay is initiated to prevent nuisance switchovers. After the delay (see Table 2 below), the alarm panel indicates “standby pump on” and the common alarm contacts close, while the standby pump is brought on to resume flow and the chiller pump is locked out. This mode is locked in until the reset button is pressed.

Similarly, if the thermostat senses high fluid temperature, a time delay is initiated to prevent nuisance switchovers. After the delay (see Table 2 below), the alarm panel indicates “standby cooling on” and the common alarm contacts close, while the solenoid valve is energized to resume cooling. This mode is locked in until the reset button is pressed.

Table 2	Time delay settings
			Delay (seconds)
Condition		Default
			Minimum	Maximum
Loss of Flow		10	0	90
High Water Temp.		180	0	480

Note that during normal operation, the auto/manual switches (see Figure 8) are set to “auto”. The switch can be set to “manual” to force switchovers to standby pump and/or standby cooling for trouble- shooting or maintenance.

Note that the “remote shutdown” function (see 4.0 - Installation) prevents emergency switchover operation regardless of the status of other controls.

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