Purge Gas Lines; Sequence Of Operation - Bryant 355BAV Installation, Start-Up, And Operating Instructions Manual

Fig. 40 - - Example of Setup Switch in Off Position
5. Remove funnel and tube from inducer housing and replace
drain connection cap and clamp.

Purge Gas Lines

If not previously done, purge the lines after all connections have
been made and check for leaks.
WARNING
!
FIRE AND EXPLOSION HAZARD
Failure to follow this warning could result in a fire,
explosion, personal injury, or death.
Never purge a gas line into a combustion chamber.
Never test for gas leaks with an open flame. Use a
commercially available soap solution made specifically
for the detection of leaks to check all connections.

Sequence of Operation

Using schematic diagram, follow sequence of operation through
different modes. (See Fig. 23.) Read and follow wiring diagram
carefully.
CAUTION
!
UNIT MAY NOT OPERATE
Failure to follow this caution may result in intermittent unit
operation.
Furnace control must be grounded for proper operation, or
control will lock out. Control is grounded through
green/yellow wire routed to gas valve and burner box
screw.
NOTE: If a power interruption occurs during a call for heat
(W/W1 or W/W1- -and- -W2), the control will start a 90- -second
blower- -only ON period two seconds after power is restored, if the
thermostat is still calling for gas heating. The amber LED light will
flash code 12 during the 90- -second period, after which the LED
will be ON continuous, as long as no faults are detected. After the
90- -second period, the furnace will respond to the thermostat
normally.
The blower door must be installed for power to be conducted
through the blower door interlock switch ILK to the furnace
control CPU, transformer TRAN, inducer motor IDM, blower
motor BLWM, hot- -surface igniter HSI, and gas valve GV.
SINGLE- - STAGE THERMOSTAT AND TWO- -
STAGE
HEATING (ADAPTIVE MODE)
See Fig. 19 or 50 for thermostat connections.
NOTE: Low- -heat- -only switch, SW1- -2, selects either the low
heat- -only operation mode when ON, (see item 2. below) or
adaptive heating mode when OFF, in response to a call for heat.
(See Fig. 33.) When the W2 thermostat terminal is energized, it
will always cause high- -heat operation when the R to W circuit is
closed, regardless of the setting of the low- -heat only switch.
A04001
This furnace can operate as a two- -stage furnace with a single- -stage
thermostat because furnace control CPU includes a programmed
adaptive sequence of controlled operation, which selects low- -heat
or high- -heat operation. This selection is based upon the stored
history of the length of previous gas heating periods of the
single- -stage thermostat.
The furnace will start up in either low- - or high- -heat. If the furnace
starts up in low- -heat, the furnace control CPU determines the
low- -heat on time (from 0 to 16 minutes) which is permitted before
switching to high- -heat.
If power is interrupted, the stored history is erased. When this
happens, the control CPU will initially select low- -heat for up to 16
minutes and then switch to high- -heat, as long as the thermostat
continues to call for heat. Subsequent selection is based on stored
history of thermostat cycle times.
The wall thermostat "calls for heat," closing the R to W circuit.
The furnace control CPU performs a self- -check, verifies the
low- -heat and high- -heat pressure switch contacts LPS and HPS are
open.
37