Sequence of Operation, Than or

If thermistor is shorted or open, replace it to return the system to

normal operation. If fault is in the wiring connections, correcting the fault will clear the code and return the system to normal operation.

NOTE: If fault condition is an open thermistor or a wiring problem

that appears to be an open thermistor and the power to the unit is

cycled off, the fault code will be cleared on the next power-up but the fault will remain and system operation will not be as expected.

This is because on power-up, the unit control cannot discern

the difference between an open sensor or if a sensor is not installed.

Sequence of Operation

The 48XL packaged unit is designed for installation with a

communicating UI. This unit will not respond to commands

provided by a common thermostat except under certain emergency

situations described in Step l--Start-Up and Troubleshooting.

The UI uses temperature, humidity and other data supplied from

indoor and outdoor system components to control heating or cooling system for optimum comfort. The unit will be commanded by UI to supply airflow. The unit will operate the indoor blower at requested airflow for most modes.

INDOOR AIRFLOW ADJUSTMENTS

The nominal requested airflow for air conditioner operations will be 350 cfm per ton of nominal cooling capacity as defined by unit

size. Actual airflow request will be adjusted from nominal using

indoor and outdoor temperature and indoor humidity data to

optimize the system operation for occupant comfort and system efficiency. Refer to UI literature for further system control details.

UNIT OPERATION HAZARD

Failure to follow this caution may result in unit damage.

For cooling operation, the recommended airflow is 350 to 450 cfm for each 12,000 Btuh of rated cooling capacity. For

heating operation, the airflow must produce a temperature rise that falls within the range stamped on the unit rating plate.

For gas

heat

operations,

Table

shows

the

temperature

rise

each

gas heating

mode.

Refer

these

tables

to determine

the

desired

heating

airflow

for

the

system

being

installed.

NOTE:

sure

that

all

supply-and

return-air

grilles

are

open,

free from

obstructions,

and

adjusted

properly.

Airflow

can

changed

using

the

UI.

See

installation

instructions

for

detail.

NOTE:

Once

the

compressor

has

started

and

then has

stopped,

should not be started again until 4 minutes have elapsed. The

cooling cycle remains :'on" until the room temperature drops to

point that is slightly below the cooling control setting of the UI.

AIR CONDITIONER SEQUENCE OF OPERATION

COOLING OPERATION

With a call for first stage cooling, the outdoor fan, and low stage

compressor	are energized.		If	low-stage	cannot		satisfy	cooling
demand,	high-stage	cooling	is	energized	by	the	UI. After second
stage is satisfied,		the unit returns		to low-stage		operation		until first

stage is satisfied or until second stage is required again. When both

first stage and second stage cooling are satisfied, the compressor will shut off.

NOTE: When two-stage unit is operating at low-stage, system

vapor (suction) pressure will be higher than a standard single-stage

system	or high-stage		operation.
NOTE:		Outdoor	fan motor	will continue	to operate	for one
minute	after	compressor	shuts off,	when outdoor	ambient	is greater
than or	equal	to 100°F	(38°C).

UTILITY INTERFACE WITH INFINITY CONTROL

The utility curtailment relay should be connected to factory

supplied pigtails (PINK, connected to R, VIOLET connected to Y2 on the control board) located in the low voltage splice box (See Fig. 13, 14 and 16). This input allows a power utility device to

interrupt compressor operation during peak load periods. When the utility sends a signal to shut the system down, the UI will display

"Curtailment Active".

COMPRESSOR OPERATION

When the compressor is operating in low stage, the modulating

ring is deactivated, allowing two internal bypass ports to close off

33% of the scroll compression area so the system operates at part

load capacity. The 24-volt solenoid coil is de-energized in

low-stage operation.

When the compressor is operating at high stage, the modulating

ring is activated, sealing the bypass ports, which allows the

compressor to operate at full load capacity. The 24-volt solenoid coil is energized in high stage operation.

CRANKCASE HEATER OPERATION (IF APPLICABLE)

The crankcase heater is energized during off cycle below 65°F (18 ° C) outdoor air temperature.

OUTDOOR FAN MOTOR OPERATION

The outdoor unit control energizes the outdoor fan any time the

compressor is operating. The outdoor fan remains energized if a

pressure switch or compressor overload should open. Outdoor fan motor will continue to operate for one minute after the compressor

shuts off when the outdoor ambient is greater than or equal to

100°F (38°C).

TIME DELAYS-AIR CONDITIONER OPERATIONS The unit time delays include:

•Five minute time delay to start cooling operation when there is a call from the thermostat or user interface. To bypass this feature,

momentarily short and release Forced Defrost pins.

•Five minute compressor recycle delay on return from a

brown-out condition.

•Two minute time delay to return to standby operation from last

valid communication (with Infinity only).

•One minute time delay of outdoor fan at termination of cooling mode when outdoor ambient is greater than or equal to 100°F

(38°C).

•There is no time delay between air conditioner staging from low to high and from high to low capacity; the compressor will change

from low to high and from high to low capacity as demand dictates.

Carrier 48XL installation instructions Sequence of Operation, than or

Models: 48XL

Sequence of Operation

than or