Service Manual

40
TWO STAGE
NON- COMMUNICATING N4A7/N4H6
These units are non- communicating and utilize 2- stage
scroll technology. These units require variable speed
furnaces that are compatible with two- stage operation (such
as F/G8MVL) or newer model variable speed fan coils
(FVM4X). Variable speed fan coils prior to the FVM4X will
NOT be rated with the new Performance series two- stage
units as they are not capable of meeting the air flow
requirements necessary for rating. These are designed to
operate with basic 24 volt thermostat inputs.
Operating Ambient
The minimum outdoor operating ambient in cooling mode is
55_F / 12.78_C, and the maximum outdoor operating
ambient in cooling mode is 125_F / 51.67_C when operating
voltage is 230v. For 208v applications, the maximum
outdoor ambient is 120_F/ 48.9_C.
NOTE: Units operating at high stage operation, 208v (or
below) line voltage and at an outdoor ambient of 120_F(or
greater), may experience compressor trip.
NOTE: This product is not approved for low ambient cooling
at this time, and no low ambient kit is available.
Airflow Selections (ECM Furnaces)
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 connected 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 connected 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 different 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 required 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 required 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
Installation Instructions for details of how to use this
feature.
Airflow Selection for FVM4X Fan Coils
(non- communicating)
The FVM4X 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 FVM4X
Installation Instructions. The FVM4X 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.
SYSTEM FUNCTION AND SEQUENCE
OF OPERATION (N4A7/N4H6)
NOTE: Defrost control board is equipped with 5 minute
lockout timer that is initiated upon any interruption of power.
Turn on power to indoor and outdoor units. Transformer is
energized.
These models utilize a 2- stage indoor thermostat. With a
call for first (low) stage cooling or heating, the outdoor fan
and low- stage compressor are energized. If low- stage
cannot satisfy cooling or heating demand, high- stage is
energized by the second (high) stage of the indoor
thermostat. After the second stage is satisfied, the unit
returns to low- stage operation until second stage is
required again. When both, first and second stage cooling
or heating are satisfied, the compressor will shut off.
Cooling
With first stage cooling, Y and O are powered on; and with
second stage cooling, Y2, Y and O are powered on. The O
energizes the reversing valve, switching it to cooling
position. The Y signal sends low voltage through the
safeties and energizes the T1 terminal on the circuit board.
If the compressor has been off for 5 minutes, or power has
not been cycled for 5 minutes, the OF2 relay and T2
terminal will energize. This will close the contactor and start
the outdoor fan motor and compressor. When the cycle is
complete, Y is turned off, stopping the compressor and
outdoor fan. The 5 minute time guard begins counting.
Compressor will not come on until this delay expires. In the
event of a power interruption, the time guard will not allow
another cycle for 5 minutes.
Heating
With first stage heating, Y is powered on; with second stage
heating, Y2 and Y are powered on. The Y signal sends low
voltage through the safeties and energizes the T1 terminal
on the circuit board. If the compressor has been off for 5
minutes or power has not been cycled for 5 minutes, the
OF2 relay and T2 terminal will energize. This will close the
contactor and start the outdoor fan motor and compressor.
When the cycle is complete, Y is turned off, stopping the
compressor nd outdoor fan. The 5 minute time guard