Bedienungsanleitung Carrier 48 50PM C16-28 (Seite 23 von 188) (Englisch)

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Economizer

If an economizer is installed, then Economizer Installed configuration

(Configuration→UNIT→EC.EN) should be set to YES. The

economizer is controlled by the economizer output signal

(Outputs→ECON→EC.CP) on the ECB control. If the indoor fan is

off or the building is unoccupied, the economizer position is zero. If in

Occupied mode and the unit is heating or cooling and the economizer

cannot provide free cooling, the economizer position is the configured

economizer minimum position (Configuration→ECON→EC.MN)

or the position specified by the IAQ algorithm. If in Unoccupied

mode, the position is 0% open.

The economizer will be allowed to help with cooling if the outdoor-air

temperature (Temperature→AIR.T→OAT) is less than the configured

economizer high temperature lockout (Setpoints→EH.LO) and

greater than the configured economizer low temperature lockout

(Setpoints→EL.LO). If an enthalpy sensor is installed, the outdoor

temperature must be below the economizer high temperature lockout

and the enthalpy (Inputs→GEN.I→ENTH) must be LOW. If a return

air temperature (RAT) sensor is installed and Diff Dry Bulb Control

(Configurations→ ECON → DF.DB = Enable) is enabled, the

outdoor air temperature must be lower than the return air temperature

in addition to the the lockouts and enthaply. For

cooling, the economizer position can vary between the configured

economizer minimum position (Configuration→ECON→EC.MN)

and the economizer maximum cooling position

(Configuration→ECON→EC.MX).

Thermostat Control

If the unit is in cooling, operating under thermostat control, Y1 = ON,

and the economizer is available for cooling, the economizer will

control the supply-air temperature to the low cool set point

(Setpoints→LCSP). When Y2 = ON, the economizer will control the

supply-air temperature to high cool set point (Setpoints→HCSP).

Space Sensor Control

If the unit is in cooling, operating under space temperature control,

the economizer is available for cooling, and no compressors are

operating, the economizer will control the SAT to either

Setpoints→LCSP or Setpoints→HCSP (See Table 8.) If a

compressor is ON, the economizer will try to position

itself at the economizer maximum cooling position

(Configuration→ECON→EC.MX).

If the control senses low suction pressure for any active refrigerant

circuit when the economizer is also providing cooling, the

maximum allowable economizer position will be reduced. Factory

default configurations have been qualified over a large range of

conditions and should only be changed with care. For unit

troubleshooting, factory default maximum economizer limits for

this condition are provided in Table 9.

Table 8 – LCSP and HCSP Transitions for

Space Temperature Mode

CURRENT SAT

SET POINT

COOL DEMAND

(∆F)

NEXT SAT

SET POINT

LCSP >0.5 HCSP

HCSP <0 LCSP

LCSP <–0.5 Exit Cooling

LEGEND

HCSP - High Cool Set Point

LCSP - Low Cool Set Point

SAT - Supply-Air Temperature

Table 9 – Maximum Economizer Limits

During Low Suction Pressure

COOLING

STAGE

SIZES

03‐07

SIZES

08‐14 SIZE 16 SIZES

20-28

Bottom 50 50 50 50

Middle — — 35 50

Top — 25 25 0

Economizer Actuator Communications

The actuator used with 48/50PG and PM 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 determines the

communication method, either digital or analog, used to

communicate between the ECB and the economizer actuator.

Economizer Control Type is accessible via the Scrolling Marquee

at Configurations→ECON→E.CTL. The power to the unit

must be cycled after E.CTL is changed.

NOTE: If unit is equipped with Adaptive Fan, the control

automatically defaults the economizer control type to 1 (E.CTL =

1) and controls the actuator digitally. This is because the analog

signal from the ECB is used to drive the VFD’s speed and therefore

can not be used to control the actuator. The field connection

terminal block TB−8 no longer represents the commanded or

actual position of the actuator.

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

When E.CTL is set to 1, the ECB will communicate with the

economizer actuator using the digital protocol, from ECB J7−1 to

actuator pin 5. The commanded position and the actuators actual

position are communicated back and forth between actuator and

ECB. When the ECB and actuator first initiate communication, a

control angle (Operating Modes→ECON→C.ANG) is provided to

the ECB and represents the actuator’s range of motion. This control

angle must be greater then the minimum angle

(Configurations→ECON→M.ANG).

During this digital control, the ECB’s analog 4 to 20mA 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 10−v signal that is accessible via field connection 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 ECB will NOT communicate with the

economizer actuator using the digital MFT. It will instead control

the actuator directly with the 4 to 20 mA analog signal wired to

TB−8 and TB−9 along with the 500−ohm resistor producing a 2 to

10−v signal for the actuator. While in this mode, the actuator’s

built−in 2 to 10−v feedback signal is accessible via TB−9 and

TB−10 any time because it is not used by the ECB.

Unoccupied Free Cooling

The unoccupied free cooling algorithm attempts to maintain the

building space temperature half way between the occupied cool

and occupied heat setpoints using only the economizer when the

conditions in the building and the outdoors are suitable. Three

different configurations define this algorithm: Unoccupied Free

Cooling (Configuration→ECON→UEFC), Free Cooling

Preoccupancy Time (Configuration→ECON→FC.TM) and Free

Cool Low Temp Limit (Configuration→ECON→FC.LO).

UEFC = 0 (Disabled)

When UEFC = 0, unoccupied free cooling is disabled. Cooling

will only occur if the space exceeds the unoccupied setpoints.

UEFC = 1 (Unoccupied)

When UEFC is set to 1, unoccupied free cooling can occur

throughout the entire unoccupied period. The space temperature

must be higher then the mid−point between the occupied cooling

and heating setpoints.

UEFC = 2 (Preoccupancy)

When UEFC is set to 2, unoccupied free cooling can only occur

when the time until the next occupied period is less than the Free

Cool PreOcc Time (FC.TM) in minutes.

48/50PG and PM

Carrier 48 50PM C16-28 Seite 23

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