Wiring Diagrams; Troubleshooting - Carrier 58CVA Installation, Start-Up, Operating And Service And Maintenance Instructions

55. Terminal EAC-1 is energized as long as the blower motor
BLWM is energized.
During a call for heat, the furnace control CPU will transition
the blower motor BLWM to continuous blower airflow,
low-heat airflow, or the midrange airflow, whichever is
lowest. The blower motor BLWM will remain ON until the
main burners ignite then shut OFF and remain OFF for the
blower-ON delay (45 seconds in low-heat, and 25 seconds in
high-heat), allowing the furnace heat exchangers to heat up
more quickly, then restarts at the end of the blower-ON delay
period at low-heat or high-heat airflow respectively.
The blower motor BLWM will revert to continuous-blower
airflow after the heating cycle is completed. In high-heat, the
furnace control CPU will drop the blower motor BLWM to
low-heat airflow during the selected blower-OFF delay period
before transitioning to continuous-blower airflow.
When the thermostat "calls for low-cooling", the blower motor
BLWM will switch to operate at low-cooling airflow. When
the thermostat is satisfied, the blower motor BLWM will
operate an additional 90 seconds at low-cooling airflow before
transitioning back to continuous-blower airflow.
When the thermostat "calls for high-cooling", the blower
motor BLWM will operate at high cooling airflow. When the
thermostat is satisfied, the blower motor BLWM will operate
an additional 90 seconds at high-cooling airflow before
transitioning back to continuous-blower airflow.
When the R to G circuit is opened, the blower motor BLWM
will continue operating for an additional 5 seconds, if no other
function requires blower motor BLWM operation.
Continuous Blower Speed Selection from Thermostat -To
select different continuous-blower airflows from the room
thermostat, momentarily turn off the FAN switch or push-
button on the room thermostat for 1-3 seconds after the blower
motor BLWM is operating. The furnace control CPU will shift
the continuous-blower airflow from the factory setting to the
next highest CF selection airflow as shown in Fig. 55.
Momentarily turning off the FAN switch again at the thermo-
stat will shift the continuous-blower airflow up one more
increment. If you repeat this procedure enough you will
eventually shift the continuous-blower airflow to the lowest
CF selection as shown in Table 1. The selection can be
changed as many times as desired and is stored in the memory
to be automatically used following a power interruption.
7. Heat pump
See Fig. 26-29 for thermostat connections.
When installed with a heat pump, the furnace control auto-
matically changes the timing sequence to avoid long blower
off times during demand defrost cycles. Whenever W/W1 is
energized along with Y1 or Y/Y2, the furnace control CPU
will transition to or bring on the blower motor BLWM at
cooling airflow, low-heat airflow, or the midrange airflow,
whichever is lowest. The blower motor BLWM will remain on
until the main burners ignite then shut OFF and remain OFF
for 25 seconds before coming back on at heating airflow.
When the W/W1 input signal disappears, the furnace control
begins a normal inducer post-purge period while changing the
blower airflow. If Y/Y2 input is still energized the furnace
control CPU will transition the blower motor BLWM airflow
to cooling airflow. If Y/Y2 input signal disappears and the Y1
input is still energized the furnace control CPU will transition
the blower motor BLWM to low-cooling airflow. If both the
Y1 and Y/Y2 signals disappear at the same time, the blower
motor BLWM will remain on at low-heat airflow for the
selected blower-OFF delay period. At the end of the blower-
OFF delay, the blower motor BLWM will shut OFF unless G
is still energized, in which case the blower motor BLWM will
operate at continuous blower airflow.
8. Component test
The furnace features a component test system to help diagnose
a system problem in the case of a component failure. To
initiate the component test procedure, ensure that there are no
thermostat inputs to the control and all time delays have
expired. Turn on setup switch SW1-6. See Fig. 32.
NOTE: The component test feature will not operate if the control
is receiving any thermostat signals or until all time delays have
expired.
The component test sequence is as follows:
a. The furnace control CPU turns the inducer motor ON at
high-heat speed and keeps it ON through step c.
b. After waiting 10 seconds the furnace control CPU turns the
hot surface igniter ON for 15 seconds, then OFF.
c. The furnace control CPU then turns the blower motor
BLWM on at midrange airflow for 15 seconds, then OFF.
d. After shutting the blower motor OFF the furnace control
CPU switches the inducer to low-heat speed for 10 sec-
onds, then OFF.
NOTE: The EAC terminals are energized when the blower is
operating.
After the component test is completed , 1 or more status codes (11,
25, or 41) will flash. See component test section or Service Label
(Fig. 50.) for explanation of status codes.
NOTE: To repeat component test, turn setup switch SW1-6 to
OFF and then back ON.
Step 4—Wiring Diagram
Refer to wiring diagram Fig. 51.
Step 5—Troubleshooting
Refer to the service label. (See Fig. 50—Service Label.)
The Troubleshooting Guide can be a useful tool in isolating
furnace operation problems. Beginning with the word "Start,"
answer each question and follow the appropriate arrow to the next
item.
The Guide will help to identify the problem or failed component.
After replacing any component, verify correct operation sequence.
A more detailed Troubleshooting Guide is available from your
distributor.
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