Carrier 48/50PD05 manual Outdoor Fan Operation, Economizer Operation, Unoccupied Free Cooling

Outdoor Fan Operation

The 48/50 PD units use a multi-speed outdoor fan motor to control the head pressure within an acceptable range at low outdoor ambient temperatures. On the 48 and 50 PD-05 and 06 size units the outdoor fan contactor is powered on the load side of the compressor contactor so the outdoor fans will run only when the compressor contactor is energized. When the outdoor fan contactor is not energized the outdoor fan runs at high speed.

When the outdoor fan contactor is energized the outdoor fan runs at low speed.

The outdoor fan speed is controlled by a system three of fan levels set up in the control software. Table 6 shows the three levels and fan speeds for each level. The fan levels are determined by Outdoor Air Temperature (Temperatures→AIR.T→OAT) but can be overridden by Condenser Pressure A (Pressures→SCP.A) inputs to the Main Base Board.

FAN	FAN	CONDITIONS TO TRANSITION TO NEXT	CONDITIONS TO TRANSITION TO NEXT
LEVEL	SPEED	LOWER LEVEL	HIGHER LEVEL
			1. Compressor Contactor is ON
			(on initial start up outdoor fan runs at Level 2 for
0	OFF	N/A	10 seconds before moving to correct level based
			on outside air temperature or Condenser Pres-
			sure A)
			1. Outside Air Temperature Control — Fan
			Lev2 On Temperature 55 F or above (Configu-
1	LOW	1. Compressor Contactor is OFF	ration→COOL→OFC→2.ON >=55F)*
			2. Condenser Pressure A Override — Fan
			Lev1 Max Pressure 450 psig or above (Config-
			uration→COOL→OFC→1.MXP>= 450 psig)*
		1. Outside Air Temperature Control --- --- Fan
		Lev2 Off Temperature 45 F or below (Confi-
2	HIGH	guration→COOL→OFC→2.OFF <=45F)*	N/A
		2. Condenser Pressure A Override --- --- Fan
		Lev2 Min Pressure 200 psig or below (Config-
		uration→COOL→OFC→2.MNP<= 200 psig)*

Table 6 — Fan Level Control of Outdoor Fan

*Configuration parameters 1.MXP, 2.MNP, 2.ON and 2.OFF factory default configuration should not be changed. The default configurations have been qualified over a wide range of conditions and are provided in case a field replacement of the control board occurs and the settings need to be checked or manually configured.\

48/50PD

Economizer Operation

If an economizer is installed, then Economizer Installed (Configuration→UNIT→EC.EN) should be set to YES. The economizer is controlled by the Econo Commanded Position (Outputs→ECON→EC.CP) on the Economizer Control Board (ECB). Feed back from the economizer actuator is output on

configuration parameter Econo Actual Position (Outputs→ECON→EC.AP).

Economizer Actuator Communication

The economizer actuator used with the 48/50PD units is a Multi-Function Technology (MFT) actuator. This allows the ComfortLink system to communicate with the actuator through a feedback signal. The configuration Economizer Control Type (Configuration→ECON→E.CTL) determines the communication method, either digital or analog, used to communicate between the Economizer Control Board and the economizer actuator.

The power to the unit must be cycled after the Economizer Control Type (Configuration →ECON→E.CTL) configuration parameter is changed.

E.CTL = 1 or 2 (Digital/Position or Digital/Command)

When Economizer Control Type (Configuration→ECON→E.CTL) is set to 1, the Economizer Control Board will communicate with the economizer actuator using the digital protocol, from Economizer Control Board plug J7-1 to actuator pin 5. The commanded position and the actuators actual position are communicated back and forth between the actuator and the Economizer Control Board. When the Economizer Control Board and actuator first initiate communication, a Control Angle Economizer Control Type (Operating Modes→ ECON→C.ANG) is provided to the Economizer Control Board and defines the actuator’s range of motion. The control angle must be greater than the Min Actuator Ctrl Angle (Configuration→ECON→M.ANG). During this digital control, the Economizer Control Board analog 4 to 20 mA output will represent the actuator’s actual position when E.CTL = 1 or

commanded position when E.CTL = 2. Because the wiring has a built-in 500-ohm resistor, the 4 to 20mA signal is converted to a 2 to 10VDC signal that is accessible via a field connected terminal board TB-8 and TB-9. However, before this signal can be read remotely, the violet wire that connects the actuator to field connection terminal board TB-J10-8 must be removed or cut.

E.CTL = 3 (Analog Control)

When E.CTL is set to 3, the Economizer Control Board will NOT communicate with the economizer actuator directly with the 4 to 20mA analog signal wired to TB-8 and TB-9 along with the 500-ohm resistor producing a 2 to 10VDC signal for the actuator. While in this mode, the actuator’s built-in 2 to 10VDC feedback signal s accessible via TB-9 and TB-10 any time because it is not used by the Economizer Control Board.

Free Cooling

The economizer will be allowed to help with cooling if the Outdoor Air Temperature (Temperatures→AIR.T→OAT) is less than the configured Econo Cool Hi Temp Limit (Configuration→ECON→EH.LO) and greater than the

configured Econo Cool Lo Temp Limit (Configuration→ECON→EL.LO). If an enthalpy sensor is installed, the outdoor temperature must be below the Econo Cool Hi Temp Limit (Configuration→ECON→EH.LO) and the Outdoor Enthalpy Switch (Inputs→GEN.I→ENTH) must be LOW.

Unoccupied Free Cooling

The unoccupied free cooling algorithm attempts to maintain the building space half way between the Occupied Cool Set Point (Setpoints→OCSP) and Occupied Heat Set Point (Setpoints→OHSP) using only the economizer when the conditions in the building and the outdoors are suitable., during UNoccupied periods if the air in the building and the outdoor air are suitable. Three different configurations define this algorithm:

1. Unoccupied	Free	Cooling
(Configuration→ECON→UEFC)

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