Service Manual

SERVICE AND MAINTENANCE FAN COILS
496 08 8001 02 11
Specifications subject to change without notice.
Use following procedure to check low voltage signals:
The ECM motor in these fan coils receive low voltage signals
from the Easy Select Board through the wiring harness
assembly. The combination of pins energized at the motor
determines the speed the motor will run. The procedure below
isolates the fan coil from all external devices such as a
thermostat, condensing unit, humidifier or electronic air
cleaner. There is also a specific troubleshooting example to
demonstrate the process. Table 7 provides information needed
to verify that the correct voltages are present at the motor and
the Easy Select Board.
THERMOSTAT:
1. Remove all thermostat and accessory wires from Easy
Select Board.
2. On Easy Select Board, jumper screw terminals (1 at a
time): R−G, R−Y/Y2, R−Y1, R−W1, R−W2. If motor runs
in all cases, check thermostat outputs. Thermostat wires
may be broken, or thermostat may be miswired,
configured incorrectly, or defective. If the motor does not
run, or runs in some cases, but not others, continue this
procedure to check wiring harness and circuit board.
WIRING HARNESS:
1. Remove 16−pin plug from motor.
2. Check for appropriate voltages on 16−pin connector
with screw terminals jumpered. (See Table 2.)
3. If signals check correctly, and motor does not run,
inspect wiring harness for loose pins or damaged plastic
that could cause poor connections.
4. If connections are good, either control module or motor
is defective.
5. If proper signals are not present, check circuit board
using procedure below:
12−PIN PLUG (PL−1) ON Easy Select Board:
1. Completely disconnect wire harness from Easy Select
Board.
2. Jumper the screw terminals one at a time; R−G,
R−Y/Y2, R−Y1, R−W1, R−W2 and check for appropriate
voltages on the Easy Select Board pins. If proper
signals are not present, replace Easy Select Board. If
proper signals are present at the pins and not at 16−pin
connector to the motor, the wiring harness is defective.
TROUBLESHOOTING EXAMPLE:
Motor is not running on a call for heat pump heating after
jumpering the Easy Select Board screw terminals as
described in Thermostat section above.
With all thermostat wires removed from Easy Select Board,
place a jumper wire between R and Y/Y2 low−voltage screw
terminals on the Easy Select Board.
1. Check Table 4 for pin number on 16−pin connector
associated with the Y/Y2 signal. The correct pin is No.
14. The far right column of Table 4 shows that (−) 12Vdc
should be present between Pin No. 14 and Pin No. 1
(common) on the 16−pin connector.
2.
Set meter to read DC voltage. Place meter leads
between Pins No. 1 (common) and No. 14 and check for
(−) 12Vdc. If signal is present, the problem is in the
module or motor. If signal is not present, the problem is
either in wiring harness or Easy Select Board.
These steps can be repeated for other modes of operation.
To check Easy Select Board:
1. Leave jumper wire in place between R and Y/Y2.
2. Check Table 4 under Volt Meter on Easy Select Board
Plug column and row for Pin No. 14 on motor plug to
see pin number on Easy Select Board that should have
voltage. The correct pin is No. 2. The column on far right
will show voltage that should be present between Pin
No. 2 and Pin No. 9 (common).
3. Place meter leads between Pins No. 2 and No. 9 on
Easy Select Board and check for (−) 12Vdc.
4. If voltage is present, the wiring harness is bad. If not, the
Easy Select Board is bad.
Verify Motor Winding Section:
Before proceeding with module replacement, check the
following to ensure motor winding section is functional. With
control module removed and unplugged from winding section:
1. The resistance between any two motor leads should be
similar.
2. The resistance between any motor lead and the
unpainted motor end plate should be greater than
100,000 ohms.
If motor winding fails one of these tests, it is defective and
must be replaced.
F. Dehumidify Mode
NOTE: Humidistat must open on humidity rise.
Latent capacities for systems using the FVM4 fan coils are
better than average systems. If increased latent capacity is an
application requirement, the field wiring terminal block
provides connection terminals for use of a standard
humidistat. The FVM4 fan coils will detect the humidistat
contacts opening on increasing humidity and reduce its airflow
to approximately 80 percent of nominal cooling mode airflow.
This reduction will increase the system latent capacity until the
humidity falls to a level which causes the humidistat to close
its contacts. When the contacts close, airflow will return to 100
percent of the selected cooling airflow. To activate this mode,
remove jumper J1 and wire in a standard humidistat. Carefully
consult product airflow data for cooling and dehumidification
modes.
Table 4 – FVM4 Motor Control Test Values (With 16−pin connector at motor unplugged)
Terminals
Jumpered
Volt Meter on 16-pin Harness
Plug
Volt Meter on 12-pin
Easy Select Board Plug
Voltage
+ - + -
R to W1 Pin 2 Pin 1 Pin 7 Pin 9 24Vac
R to W2 Pin 13 Pin 1 Pin 4 Pin 9 24Vac
R to Y1 Pin 6 Pin 1 Pin 3 Pin 9 (-)12Vdc
R to Y/Y2 Pin 14 Pin 1 Pin 2 Pin 9 (-)12Vdc
R to G (LO) Pin 15 Pin 1 Pin 3 Pin 9 0Vac
R to G (MED) Pin 6 Pin 1 Pin 3 Pin 9 (-)12Vdc
R to G (HI) Pin 14 Pin 1 Pin 2 Pin 9 (-)12Vdc