Carrier 30RY/RYH, 30RA/RH Evaporator water pump control, Control interlock contact, Control point

PARAMETER STATUS

ON/OFF	CONTROL	HEATING/COOLING	REMOTE HEATING/	HC_SEL	OUTDOOR TEMPERATURE	OPERATING
STATUS	TYPE	SELECTION IN	COOLING CONTACTS			MODE
		LOCAL MODE
Off	-	-	-	-	-	Cooling
On	Local	Cooling	-	-	-	Cooling
On	Local	Heating	-	-	-	Heating
On	Local	Auto	-	-	> Cooling threshold	Cooling
On	Local	Auto	-	-	< Heating threshold	Heating*
On	Local	Auto	-	-	Between cooling and heating thresholds	Standby
On	Remote	-	Cooling mode	-	-	Cooling
On	Remote	-	Heating mode	-	-	Heating
On	Remote	-	Auto mode	-	> Cooling threshold	Cooling
On	Remote	-	Auto mode	-	< Heating threshold	Heating*
On	Remote	-	Auto mode	-	Between cooling and heating thresholds	Standby
On	CCN	-	-	Cooling	-	Cooling
On	CCN	-	-	Heating	-	Heating
On	CCN	-	-	Auto	> Cooling threshold	Cooling
On	CCN	-	-	Auto	< Heating threshold	Heating*
On	CCN	-	-	Auto	Between cooling and heating thresholds	Standby

*Does not apply to cooling only units that do not control a boiler.

5.3 - Evaporator water pump control

The unit can control one or two evaporator water pumps. The evaporator water pump is turned on when this option is configured (see User configuration) and when the unit is in one of the on modes described above or in delay mode. Since the minimum value for the delay at start-up is 1 minute (configurable between 1 and 15 minutes), the pump will run for at least one minute before the first compressor starts. The pump is kept running for 20 seconds after the unit goes to stop mode. The pump keeps working when the unit switches from heating to cooling mode or vice-versa. It is turned off if the unit is shut down due to an alarm unless the fault is a frost protection error. The pump can be started in particular operating conditions when the evaporator heater is active (see section 5.5). See section 5.14 for the particular evaporator pump control for the follower unit (master/slave assembly).

If two pumps are controlled and the reversing function has been selected (see User 1 configuration), the control tries to limit the pump run time delta to the configured pump change- over delay. If this delay has elapsed, the pump reversing function is activated, when the unit is running. During the reversing function both pumps run together for two seconds.

If a pump has failed and a secondary pump is available, the unit is stopped and started again with this pump.

The control provides a means to automatically start the pump each day at 14.00 hours for 2 seconds when the unit is off. If the unit is fitted with two pumps, the first pump is started on odd days and the second pump is started on even days. Starting the pump periodically for few seconds increases the life-time of the pump bearings and the tightness of the pump seal.

5.4 - Control interlock contact

This contact checks the status of a loop (water flow switch and customer safety loop, see section 3.6). It prevents the unit from starting if it is open when the delay at start-up has expired. This open contact leads to an alarm shut-down, if the unit is running.

5.5 - Evaporator antifreeze protection

The heater for the evaporator and water pump cycling (for units with a pump) can be energised to protect the evaporator, if it can be damaged by freezing, when the unit is shut down for a long time at low outdoor temperature.

NOTE: Evaporator heater control parameters can be modified, using the Service configuration.

5.6 - Control point

The control point represents the water temperature that the unit must produce. The inlet water is controlled by default, but the outlet water can also be controlled (requires a Service configuration modification).

Control point = active setpoint + reset

5.6.1 - Active setpoint

Two setpoints can be selected as active in cooling mode and three in heating mode. Usually, the second cooling setpoint is used for unoccupied periods or for ice storage (brine unit). The second setpoint in heating mode is used for unoccupied periods, and the third heating setpoint is used for holiday periods or public holidays. Depending on the current opera- tions, the active setpoint can be selected by choosing the item in the Information menu, with the user’s volt-free contacts, with network commands or with the setpoint timer program (schedule 2).

31