Emerson E2 operation manual Condenser Control, Air Cooled Condensers, Air Cooled Strategy

CIRCUIT	LIQUID RECEIVER
CASE TEMP
(FOR FLOATING)
CASE CIRCUIT	LIQUID LINE		CONDENSER
	SOLENOID
	SUCTION	DISCHARGE
		PRESSURE
	PRESSURE	OIL RESET SWITCHES
	D	D	D
	OIL		26507005
PRESSURE

Figure 11-1- Diagram of a Suction Group

Input	Sensor Type	Wiring
		Instructions
Suction Pres-	100 lb. Eclipse	see Table 9-1 on
sure	transducer	page 9-3.
Discharge Pres-	500 lb. Eclipse	see Table 9-1 on
sure	transducer	page 9-3
Oil Pressure	200 lb. Eclipse	see Table 9-1 on
	transducer	page 9-3
Case Circuit	Temperature	see Table 9-1 on
Temperature		page 9-3
Oil Reset	Digital	see Table 9-1 on
Switches		page 9-3

Table 11-1- Suction Group Inputs

Output Device	Wire Output Board	Set Failsafe Dip	Notes
	Contacts to:	Switch to:
Compressor	N.C.	N.C. (up)	If you want a compressor to be OFF during network/
			power loss, use N.O. failsafes instead.
Unloader	N.C.	N.O. (down)	These fail-safe settings are specifically for unloaders.
Liquid Line Sole-	N.C.	N.C. (up)	Keeps solenoid energized during network/power loss.
noid (LLS)
Electric Defrost	N.O.	N.O. (down)	Keeps contacts de-energized during network/power loss.

Table 11-2- Suction Group Outputs

11.2 Condenser Control

An E2 RX is capable of controlling air-cooled or evap- orative condensers. The E2 RX-300 may control a single condenser, while the RX-400 may control up to two con- densers.

11.2.1 Air Cooled Condensers

An air-cooled condenser consists of one or more fans that blow air across a manifold of tubing to cool heated refrigerant and condense it into a liquid. The E2 controls condensers by activating or deactivating fans in order to maintain discharge pressure or temperature at or below a chosen setpoint.

A Condenser Control application may use either of two strategies to operate air cooled condensers: an air-cooled strategy, or a temperature differential (T-D) strategy.

11.2.1.1Air Cooled Strategy

The air cooled strategy uses a simple PID control loop

that compares a single Control In input to a PID setpoint. The resulting percentage is used to activate the condenser fan(s) necessary to bring the input value down below the setpoint.

Control inputs for air cooled strategies most commonly come from a pressure transducer mounted on either the discharge line, the condenser inlet, or the condenser outlet. However, temperature sensor values will also be accepted.

11.2.1.2Temperature Differential

Strategy

The temperature differential strategy attempts to keep a minimum amount of difference between the temperature of the refrigerant and the ambient outside temperature.

This strategy begins by determining the temperature of the refrigerant coming into the condenser. This can be sup- plied by either a temperature sensor or pressure transducer located near the condenser inlet; if it’s a pressure trans- ducer, its value will automatically be converted to a tem- perature value based upon the type of refrigerant.

Condenser Control Software Overview • 11-3