Smart Heat Operation; Electrical Operating Sequences And Troubleshooting - Carrier FA4ANF Service Manual

HEATER PART NO.
KFAEH2201H10 or
KFCEH0101H10
KFAEH2301H15 or
KFCEH0201H15
KFAEH2401H20 or
KFCEH0301H20
5. When both W3 and W2T are energized without JW1 being cut
or with outdoor thermostat closed, system operation stages
heat up to maximum level if signal is energized for proper
amount of time.
6. If only W3 is energized (JW1 is cut), there is no effect on
PCB. No heat is energized.
ACCESSORIES
Terminals AUX+ and AUX- are energized with 24 vdc when fan
is energized. The accessory kit KFAIR0101ACR is used to
connect an EAC or humidifier.
NOTE: Loads cannot be connected directly to AUX+ and AUX-.
Use the specified kit only.
BLOWER
1. Blower On Delay—To optimize comfort, there is a 30-sec
blower on delay in heat pump heating mode only.
2. Blower Off Delay—Smart Heat control uses a 60-sec off
blower delay, as opposed to the standard 90-sec delay.
Step 3—Smart Heat Operation
COOLING
The Smart Heat option controls cooling mode in same manner as
conventional heat pumps are controlled. The fan has a 90-sec delay
off/on cycle down.
HEAT PUMP HEATING
The Smart Heat option does not control heating in the conventional
method. The PCB energizes compressor 30 sec before indoor fan
is energized. This allows indoor coil to heat up eliminating
cold-blow on start-up.
The electric heat is staged-on to allow continuous operation of heat
pump and electric resistance heat below balance point (below point
where heat pump cannot maintain dwelling temperature without
supplemental heat) independent of outdoor thermostats.
Although PCB has provisions for an outdoor thermostat, it is not
needed for staging. On cycle down, indoor fan remains on 60 sec
to recover heat stored in indoor coil.
DEFROST
The Smart Heat PCB stages the correct amount of supplemental
heat during defrost. If too much heat is added, system stays in
defrost for completion of defrost cycle even though thermostat is
satisfied. On next cycle, 1 less element is energized during next
defrost period.
NOTE: If the signal from thermostat is interrupted (ie., thermo-
stat is satisfied) while unit is in defrost mode, the defrost cycle will
be completed before unit shuts down.
TROUBLESHOOTING PRINTED-CIRCUIT BOARD
(DIAGNOSTIC LED)
The PCB of Smart Heat option heater package contains a micro-
processor which controls fan operation, fan speed, outdoor unit,
and heater elements. For troubleshooting, a service LED indicates
condition of PCB. See Table 11 for LED flash codes.
Table 10—Electric Heater Stage Limiting
Heater Stage
10 kw Non-Fused
15 kw Fused
20 kw Fused
STAGES (KW OPERATING)
W2T Only (JW1 cut)
1 2
3 6
3 8
5 10
Table 11—LED Codes for Smart Heat PCB
FLASH CONDITION
No Light/Flash
Steady Light
Steady Flash
1 Flash
2 Flashes
3 Flashes
4 Flashes
5 Flashes
6 Flashes Y, W2D, and/or W2T
7 Flashes
Step 4—Electrical Operating Sequences and
Troubleshooting
NOTE: Refer to Table 12 for proper input and output voltages.
See Fig. 40 for Smart Heat Proper Wiring Diagram.
READY-TO-START
In ready-to-start (standby) mode, LED on board indicates a steady
flash.
In this mode, 24-v power should be available at control's low
voltage terminal strip terminals R and C. If 24v is not present
across R and C, check the following:
• Is low-voltage fuse on control board good?
• Are line voltage fuses FU1 and FU2 good?
• Is LED on control on steadily or not on at all? Both of these
indications signal a possible board failure.
• Is 208/230-v power available to control across pins 7 and 9
of 9-pin connector? Is connection to board tight?
CONTINUOUS FAN
On a call for continuous fan, thermostat provides a 24-v input
signal to G terminal on low-voltage terminal strip. Sensing this
signal, the microprocessor energizes a relay on control to provide
power to high-speed winding of fan motor, at 1. The fan continues
to run until fan switch on thermostat is turned off.
During continuous fan operation with no call for heating or
cooling, LED indicates a steady flash, the same indication seen
when system is in standby.
The call for continuous fan operation signal can be checked by
placing voltmeter leads across terminals G and C of control's
low-voltage terminal strip. If 24v is not seen across these termi-
nals, check for the following:
• Is 24v available across R and C? If not, refer to Ready-To-
Start section for items to check if 24v is not available.
48
W2T and W3
3
9
11
15
INPUT SIGNALS SYSTEM OPERATION
No Power or
—
Board Failure
— Board Failure
Stand By Condition
—
or Fan Only
Heat Pump Only
Y only
Operating
Heat Pump Plus
Y and/or W2T
1 Sequencer
Heat Pump Plus
Y and/or W2T
2 Sequencers
Heat Pump Plus
Y and/or W2T
3 Sequencers
Y, O Cool Mode
Defrost Mode
W2T Emergency Heat Mode
4
9
15
20