5
Airflow Selections (ECM Furnaces -- non commu-
nicating)
The ECM Furnaces provide blower operation to match the
capacities of the compressor during high and low stage cooling
operation. Tap selections on the furnace control board enable the
installing technician to select the proper airflows for each stage of
cooling. Below is a brief summary of the furnace airflow
configurations
1. The Y2 call for high stage cooling energizes the “Cool” tap
on the control board. The grey wire from cool tap is connec-
ted to tap 5 on the motor. Refer to the furnace Product Data
to find the corresponding airflow. If the airflow setting for
high cooling needs to be switched from tap 5 to a different
tap, jumper a connection from the cool tap to the desired tap
so that the Y2 signal is communicated via the cool tap to the
desired speed tap.
2. The Y1 call for low stage cooling energizes the “Fan” tap
on the control board. The red wire from the fan tap is con-
nected to tap 1 on the motor. Refer to the furnace Product
Data to find the corresponding airflow. If the airflow setting
for low cooling needs to be switched from tap 1 to a differ-
ent tap, jumper a connection from the Fan tap to the desired
tap so that the Y1 signal is communicated via the Fan tap to
the desired speed tap. The Y1 setting will also govern the
continuous fan airflow for the furnace.
Refer to the literature for the furnace for further details.
Airflow Selection for Variable Speed Furnaces
(non--communicating)
The variable speed furnaces provide blower operation to match the
capacities of the compressor during high and low stage cooling
operation. The furnace control board allows the installing
technician to select the proper airflows for each stage of cooling.
Below is a summary of required adjustments. See furnace
installation instructions for more details:
1. Turn SW1 ----5 ON for 400 CFM/ton airflow or OFF for 350
CFM/ton airflow . Factory default is OFF.
2. The A/C DIP switch setting determines airflow during high
stage cooling operation. Select the A/C DIP switch setting
corresponding to the available airflow shown in the furnace
Installation Instructions that most closely matches the re-
quired airflow shown in the air conditioning Product Data
for HIGH speed.
3. The CF DIP switch setting determines airflow during low
stage cooling operation. Select the CF DIP switch setting
corresponding to the available airflow shown in the furnace
installation instructions that most closely matches the re-
quired airflow shown in the air conditioning Product Data
for LOW speed. If a higher or lower continuous fan speed is
desired, the continuous fan speed can be changed using the
fan switch on the thermostat. Refer to the furnace Installa-
tion Instructions for details of how to use this feature.
Airflow Selection for FV4C Fan Coils (non--com-
municating)
The FV4 provides high -- and low--stage blower operation to match
the capacities of the compressor at high-- and low--stage.
To select recommended airflow , refer to the FV4C Installation
Instructions. The FV4C utilizes an Easy Select control board that
allows the installing technician to select proper airflows. This fan
coil has an adjustable blower--off delay factory set at 90 sec. for
high-- and low--stage blower operation.
When using a communicating control with the fan coil or the
furnace, dip--switch adjustments are not necessary. The outdoor
unit configuration and the indoor airflows are determined by
communicating control setup.
Start--Up
CAUTION
!
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this caution may result in personal injury,
equipment damage or improper operation.
S Do not overcharge system with refrigerant.
S Do not operate unit in a vacuum or at negative pressure.
S Compressor dome temperatures may be hot.
CAUTION
!
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal injury.
Wear safety glasses, protective clothing, and gloves when
handling refrigerant and observe the following:
S Front seating service valves are equipped with Schrader
valves.
SYSTEM FUNCTIONS AND SEQUENCE
OF OPERATION
The 24APA7 models utilize either an Infinity Communicating User
Interface or a 2-stage cooling indoor thermostat. 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
is energized by the second stage of indoor thermostat. 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. When a 2-stage unit is operating at
low-stage, system vapor (suction) pressure will be higher than a
standard single-stage system or high-stage operation.
When the outdoor ambient is more than 100_F (37.8_C), the
outdoor fan will continue to run for one minute after compressor
shuts off. this reduces pressure differential for easier starting in the
next cycle.
24APA7
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