Service Manual

SERVICE AND MAINTENANCE FAN COILS
12 496 08 8001 02
Specifications subject to change without notice.
Figure 7 − Humidistat Wiring for De−Humidify Mode
EASY SELECT
BOARD TERMINAL
BLOCK
D
H
J1
R
HUMIDISTAT
REMOVE
JUMPER
A95316
FCM4
Model FCM4 fan coil is designed to be installed with the
Observert communicating wall control. The FCM4 fan coil will
provide airflow at a rate commanded by the Observer wall
control. The nominal airflow/ton rate is 350 CFM/ton. The
Observer wall control will modify the commanded airflow under
certain operating modes. Refer to the Observer wall control
literature for further system control details. This fan coil will not
respond to commands from a common thermostat except
under certain emergency situations explained in this
document.
ELECTRONICALLY COMPUTED MOTOR ECM 3.0
An ECM 3.0 is fed high voltage AC power through the 5−pin
connector. 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 3 stator
windings. The frequency of these communication pulses
determines motor speed. The rotor is permanently
magnetized.
ECM 3.0 CONTROL POWER
The ECM 3.0 control power is supplied from R circuit through
printed circuit runs to motor control connector Plug 1, Pin 1,
through motor control harness to motor. The C side of
low−voltage control power circuit is connected by printed
circuit runs to motor connector Plug 1, Pin 2 then through
motor control harness to motor. A digital signal is sent from
Plug 1, Pins 3 and 4 to communicate with the motor including
all airflow requirements.
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.
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 plug/recp2. The ECM 3.0 power connections are
made at the transformer primary terminals. The transformer
secondary connections are made at SEC1 and SEC2
connectors.
TROUBLESHOOTING
NOTE: Always check high and low voltage supply to the fan
coil components. Check the integrity of the plug receptacle
connections and fan coil wiring harness prior to assuming a
component failure.
A. LED Description:
LEDs built into fan coil control provide installer or service
person information concerning operation and/or fault condition
of the fan coil control and ECM motor. This information is also
available at the Observer wall control in text with basic
troubleshooting instructions. Careful use of information
displayed will reduce the need for extensive manual
troubleshooting.
The amber LED located at bottom center of control adjacent to
motor harness plug is Motor Status LED, and it is labeled
MOTOR. A second amber LED, located in upper right center
of control adjacent to System Communications connector
(DX+, DX−, C, R), is the System Status LED, and it is labeled
STATUS. The green LED labeled COMM is also located
adjacent to System Communications connector, below
STATUS LED, and is used as an indicator of system
communications status. Status Codes will be displayed on the
STATUS LED using the following protocol:
1. The number of short flashes indicates first digit of code.
2. The number of long flashes indicates second digit of
code.
3. A short flash is 0.25 seconds on. A long flash is one
second on.
4. The time between flashes is 0.25 seconds.
5. The time between last short flash and first long flash is 1
second.
6. The LED will be off for 2.5 seconds before repeating
code.
B. Fan Coil Control Start−Up and System
Communications Troubleshooting:
On power up, green COMM LED will be turned off until
successful system communications are established (this
should happen within 10 seconds). Once communications with
Observer wall control are successful, COMM LED will be lit
and held on. At the same time, amber STATUS LED will be lit
and held continuously on until a request for operating mode is
received. The STATUS LED will be on any time fan coil is in
idle mode.
If, at any time, communications are not successful for a period
exceeding two minutes, fan coil control will only allow
emergency heating or cooling operation using a common
thermostat, a non−communicating outdoor unit and the R, C,
Y, O, W outdoor unit terminal strip connections and will display
Status Code 16, System Communication Fault, on amber
STATUS LED. No further fan coil troubleshooting information
will be available at Observer wall control until communications
are re−established.
If COMM LED does not light within proper time period and
status code is not displayed:
1. Check system transformer high and low voltage to be
sure the system is powered.
2. Check fuse on fan coil control to be sure it is not blown.
If fuse is open, check system wiring before replacing it
to be sure a short does not cause a failure of
replacement fuse.
If COMM LED does not light within proper time period and
status code is displayed:
Check system wiring to be sure Observer wall control is
powered and connections are made DX+ to DX+, DX− to DX−,
etc. and wiring is not shorted. Mis−wiring or shorting of the
DX+, DX−, C, R communications wiring will not allow
successful communications.