Carrier FB4 - Ffm

18
17. Check the blower motor serial output signal. The blinking
LED on the control board represents the serial output signal.
You can measure the signal with a DC voltmeter by remov-
ing Plug 1 from the circuit board (HK38AE011) and con-
necting the DC voltmeter across PL1--4 (+) and PL1--2 (--).
The voltage should be near 0Vdc but it will fluctuate briefly
several times per second. If you have an analog voltmeter,
the needle briefly will go high several times per second. If
you have a digital voltmeter with a bar graph, it will show a
large change in magnitude on the bar graph several times
per second. If you have a plain, digital voltmeter, it will
show a brief fluctuation in voltage, and the magnitude may
vary depending on the voltmeter used.
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death.
Disconnect all power to the unit before servicing the field
wires or removing the control package. The disconnect (when
used) on the access panel does not disconnect power to the line
side of the disconnect, but does allow safe service to all other
parts of the unit.
!
WARNING
The minimum maintenance requirements for this equipment are as
follows:
1. Inspect and clean or replace air filter each month or as re-
quired.
2. Inspect cooling coil, drain pan, and condensate drain each
cooling season for cleanliness. Clean as necessary. An in-
spection port is provided on all A--coil delta plates. Remove
plastic plug to inspect. Replace plug after inspection.
3. Inspect blower motor and wheel for cleanliness each heating
and cooling season. Clean as necessary.
4. Inspect electrical connections for tightness and controls for
proper operation each heating and cooling season. Service
as necessary.
CUT HAZARD
Failure to follow this caution may result in personal injury.
Sheet metal parts may have sharp edges or burrs. Use care and
wear appropriate protective clothing and gloves when handling
parts.
CAUTION
!
FILTER ASSEMBLY
To clean or replace air filter, push plastic connectors toward center
of unit and remove filter access panel outward. Push filter up and
back into unit. Then slide filter out.
Clean filter by using cold water and mild detergent. Rinse and
allow filter to dry. No oiling or coating of filter is required.
New filters are available from your local distributor. Place filter in
slot with cross--mesh binding up or facing cooling coil and replace
filter access panel.
COOLING COIL, DRAIN PAN, AND COND. DRAIN
The cooling coil is easily cleaned when it is dry. Inspect the coil
and clean (if necessary) before each cooling season. To check or
clean cooling coil, remove coil access panel. If coil is coated with
dirt or lint, vacuum it with a soft brush attachment.
Be careful not to bend coil fins. If coil is coated with oil or grease,
clean it with a mild detergent and water solution. Rinse coil
thoroughly with clear water. Be careful not to splash water on
insulation.
FFM
ELECTRICAL OPERATION HAZARD
Failure to follow this warning could result in personal injury
or death.
Before installation or servicing system, always turn off main
power to system. There may be more than one disconnect
switch. Turn off accessory heater power if applicable. Lock out
and tag switch with a suitable warning label.
!
WARNING
FAN MOTOR
The motor is three--speed direct drive. High--speed lead is black,
medium--speed lead is red, low--speed lead is blue, and common
lead is purple. Be sure proper blower speed has been selected.
The motor is turned on through two different routes. The first
occurs when thermostat calls for the fan in cooling, heat pump, or
fan--only mode. A 24--Vac signal is sent to relay, causing relay to
close its normally open contacts, turning fan on.
The second occurs when there is a call for electric heat. A 24--Vac
signal is sent to heater sequencer/relay, causing it to close, directing
230V through the normally closed contact of fan relay, turning fan
on. The fan remains on until sequencer/relay opens.
If motor does run, test motor for an open winding or a winding
shorted to motor case. If either is present, replace motor.
ELECTRIC HEATER SERVICE
Service can be completed with heater in place. Shut off power
before servicing.
A. Limit Switch
Refer to Electric Heater Kit Function and Troubleshooting section
of this manual.
B. Sequencer
Refer to Electric Heater Kit Function and Troubleshooting section
of this manual.
C. Transformer
A 40--VA transformer supplies 24--V power for control circuit.
Check for 208/230V on primary side of transformer. If present,
check for 24V on secondary side.
NOTE: Transformer is fused. Do not short circuit.
D. Fan Relay
Relay coil is 24--V. Check for proper control voltage. Replace relay
if faulty.
CLEANING OR REPLACING REFRIGERANT
FLOW--CONTROL DEVICE
The FFM piston can be removed and cleaned if believed to be
plugged. This unit’s piston is unique and replacements are
available from RCD.
The filter drier should be located on the liquid line at the indoor
unit to prevent particulate from plugging the piston.
SEQUENCE OF OPERATION
A. Condensing Unit
COOLING
When thermostat calls for cooling, the circuit between R and G is
complete and single--pole single--throw relay FR is energized. The
normally open contacts close causing blower to operate.
The circuit between R and Y is also complete. This completed
circuit causes contactor in outdoor unit to close which starts
compressor and outdoor fan.
HEATING
When thermostat calls for heating and FAN switch is set on AUTO,
the circuit between R and W is complete. The heater sequence SEQ