Bryant 355CAV User Manual

Page 51

blower--off delay is decreased from 90 seconds to 5
seconds.

Super Dehumidify Mode

Super--Dehumidify mode can only be entered if the furnace control
is in the Thermidistat mode and there is a demand for

dehumidification. The cooling operation described in item 4. above

also applies to operation with a Thermidistat. The exceptions are
listed below:

1. Low cooling – When the R to Y1 circuit is closed, R to G

circuit is open, and there is a demand for dehumidification,

the furnace blower motor BLWM will drop the blower
airflow to 65% of low--cooling airflow for a maximum of
10 minutes each cooling cycle or until the R to G circuit

closes or the demand for dehumidification is satisfied.
Low--cooling airflow is the true on--board CF selection as

shown in Fig. 47.

2. High cooling – When the R to Y/Y2 circuit is closed, R to

G circuit is open, and there is a demand for

dehumidification, the furnace blower motor BLWM will
drop the blower airflow to 65% of high--cooling airflow for

a maximum of 10 minutes each cooling cycle or until the R
to G circuit closes or the demand for dehumidification is
satisfied. High--cooling airflow is based on the A/C

selection shown in Fig. 47.

3. Cooling off--delay – When the “call for cooling” is satisfied

and there is a demand for dehumidification, the cooling
blower--off delay is decreased from 90 seconds to 5

seconds.

Continuous Blower Mode

When the R to G circuit is closed by the thermostat, the blower

motor BLWM will operate at continuous blower airflow.
Continuous blower airflow selection is initially based on the CF

selection shown in Fig. 47. Factory default is shown in Fig. 47.
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 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 the blower--ON delay (60 seconds in

medium heat, and 35 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, medium--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 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. 47. 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 will eventually shift the continuous

blower airflow to the lowest CF selection as shown in Fig. 47. The
selection can be changed as many times as desired and is stored in

the memory to be automatically used following a power
interruption.

Heat Pump

See Fig. 54--57 for thermostat connections. When installed with a

heat pump, the furnace control automatically 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 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

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.

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. 33)
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:

1. The furnace control CPU turns the inducer motor IDM ON

at medium speed and keeps it ON through step 3.

2. After waiting 15 seconds the furnace control CPU turns the

hot surface igniter ON for 15 seconds, then OFF.

3. The furnace control CPU then turns the blower motor

BLWM ON at mid--range airflow for 15 seconds, then OFF.

4. After shutting the blower motor BLWM OFF the furnace

control CPU shuts the inducer motor IDM 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, 41, or 42) will flash. See Service Label on blower access panel
or Service/Status Code Instructions for explanation of status codes.
NOTE: To repeat component test, turn setup switch SW1--6 to
OFF and then back ON.

355C