Service Manual

SERVICE AND MAINTENANCE FAN COILS
6 496 08 8001 02
Specifications subject to change without notice.
Figure 4 − FVM4 motor/ECM 5.0 Motor
NAMEPLATE
NAMEPLATE
LABEL
LABEL
A13028
FVM4
Constant Air Flow
Unlike fan coils using induction motors where static pressure
affects airflow, these fan coils are constant airflow units. The
blower delivers requested airflow regardless of static pressure.
Consult fan coil Specification Sheet for static pressure limits.
The ECM 5.0 is pre−programmed and contains airflow tables
for all modes of operation. Blower characteristics (requested
airflow, torque, and speed) are known from laboratory testing If
any two characteristics are known, the third is defined.
Requested airflow is known from Easy Select Board
configuration and thermostat signals. Torque is known
because it is directly related to stator current, which is
measured by motor control. Speed is measured by counting
back EMF pulses from stator windings. This information is
entered into an expression that calculates torque from speed
and airflow numbers. If calculation does not match stored
blower characteristics, torque is adjusted until agreement is
reached. This calculation and adjustment is performed every
0.8 seconds while motor is in operation. There is no direct
measure of static pressure, but unit does react to a change in
static to maintain constant airflow. A change in pressure will
result in a change in stator speed and torque. The motor will
begin to adjust on the next sampling, calculate new desired
speed and torque, and adjust as necessary.
INTEGRATED CONTROLS AND MOTOR ECM 5.0
An ECM 5.0 is fed high voltage AC power through the 5−pin
connector. (See Figure 4.) The AC power is then internally
rectified to DC by a diode module. After rectification, DC signal
is electronically communicated and fed in sequential order to
three stator windings. The frequency of these commutation
pulses determines motor speed. The rotor is permanently
magnetized.
An ECM 5.0 is powered with high voltage at all times. The
motor will not run with high voltage alone. Low voltage must be
applied to control plug to run motor.
ECM 5.0 Control Power
The ECM 5.0 control power is supplied from R circuit through
printed circuit runs to motor control Connector−Pin 8, through
motor control harness to motor. The C side of low−voltage
control power circuit is connected by printed circuit runs to
motor Connector −Pins 9, 10, and 11 then through motor
control harness to motor.
Low−Voltage Circuit Fusing and Reference
The low−voltage circuit is fused by a board−mounted 5−amp
automotive−type fuse placed in series with transformer SEC2
and R circuit. The C circuit of transformer is referenced to
chassis ground through a printed circuit run at SEC1
connected to metal standoff marked.
NOTE: The PCB must be mounted with two screws and motor
ground lead secured to blower housing or erratic motor
operation can result.
Transformer, Motor, and Electric Heater Power Connection
Transformer high voltage supplied from electric heater
package or high voltage leads through 12−pin heater
connector plug2/recp2. The ECM 5.0 power connections are
made at the transformer primary terminals. The transformer
secondary connections are made at SEC1 and SEC2
connectors.
PCB LAYOUT AND DESCRIPTION
NOTE: Layout of actual PCB is depicted in Figure 5.
The Easy Select Board is the interface between the ECM
motor and other system components. The board offers
choices of electric heater size, outdoor unit size and type,
comfort or efficiency settings, on and off delay profiles, and
continuous fan speed. The installer should select the correct
size of components that are being installed in each installation.
If no selections are made, the factory default settings are for
the largest heater, largest outdoor unit, AC system type,
nominal airflow adjust, and 0/90 time delay.
NOTE: Outdoor unit model should have an AHRI rating with
the variable speed fan coil. Some outdoor unit models will not
work properly with this fan coil.
Power for system is supplied from a 230−Vac, 60−Hz line.
Class 2 voltage (24 Vac nom.), used for thermostat
connections, is derived from transformer located in close
proximity to PCB. The 24−Vac secondary circuit includes
5−amp automotive−type fuse in SEC2 circuit.
Connection to heater panel is made through 12−pin connector
PL−1. Connections to thermostat are made at screw terminals.
Twenty−one pin terminals comprise field select taps for motor.