Troubleshooting - Bryant 880TA Installation, Start-Up, Operating And Service And Maintenance Instructions

Variable-speed, induced-combustion 4-way multipoise gas furnace

Hide thumbs

Table of Contents

flow. When the thermostat is satisfied, the blower motor

BLWM will operate an additional 90 seconds at low- -cool-

ing airflow before transitioning back to continuous- -blow-

er 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 sec-

onds, if no other function requires blower motor BLWM

operation.

Continuous Blower Speed Selection from Thermostat

To select different continuous- -blower airflow 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. 57. Momentarily turning off the FAN switch

again at the thermostat will shift the continuous- -blower

airflow up one more increment. If you repeat this

procedure enough

you

continuous- -blower airflow to the lowest CF selection as

shown in Fig. 57. The selection can be changed as many

times as desired and is stored in the memory to be

automatically used following a power interruption.

NOTE: If the blower- -off delay is set to the maximum, the

adjustable continuous- -fan feature is locked (i.e., fan speed cannot

be changed from its current setting).

7. Heat pump

See Fig. 29 - - 30 for thermostat connections.

When installed with a heat pump, the furnace control auto-

matically changes the timing sequence to avoid long blow-

er 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 mo-

tor BLWM at cooling airflow, low- -heat airflow, or the

mid- -range 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 air-

flow. 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

will eventually

shift the

Y1 and Y/Y2 signals disappear at the same time, the blow-

er 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 diag-

nose 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. 26.)

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 mid- -range airflow for 15 seconds, then

OFF.

d. After shutting the blower motor OFF the furnace con-

trol CPU switches the inducer to low- -heat speed for

10 seconds, 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. 52) for explanation of status codes.

NOTE: To repeat component test, turn setup switch SW1- -6 to

OFF and then back ON.

Wiring Diagram

Refer to wiring diagram Fig. 53.