f. Obstructions in the heat exchanger / exhaust venting system – Examine the heat
exchanger, vent pipe, combustion air passages, vent connectors, and chimney to be sure
they are clear and free of obstructions. Note: proper orientation on the heat exchanger is
for the compressed heat transfer blade portion
to be up and away from the burner section and
if applicable, towards the add-on indoor coil
cabinet. If there are questions regarding the
heat exchanger orientation, contact the
Johnson Controls Field Service Support staff
for further information and directions.
g. Incorrect firing rate - Verify natural gas input
rate by clocking meter. If clocked rate does not
match the input rate from the unit nameplate,
follow the steps in the manual to adjust the
manifold pressure. In addition, examine the
burner flames to make sure they are in good
adjustment. Look to a pure blue flame with a
light blue cone at its center that burns full,
steady, and straight. If yellow or orange,
partial, diverted, or unsteady flame is detected
then turn off gas valve and clean any debris
from nozzles and burners. If condition still
exists then check airflow, venting, gas pressure, etc. If condition still exists, contact the
Johnson Controls Field Service Support staff for further information and directions.
B.
FLAME PROVING SENSOR
– This sensor validates that there is flame present in the burner
(flame allows for current flow) to ensure proper combustion. It helps protect the burner from
buildup of gas without flame. If the flame is not detected within 7 s of the gas valve opening, the
gas valve is shut off and a retry operation begins. Also, if the flame is lost for 2 s during the 10 s
stabilization period, the gas valve is shut off and a retry operation begins. During a retry
operation, the vent motor starts a 15 s inter-purge, and the ignitor warm-up time is extended to 27
s. If the flame is established for more than 10 s after ignition during a retry, the control clears the
ignition attempt (retry) counter. If three retries occur during a call for heat, the furnace shuts down
for 1 h. If at the end of the 1 h shut down there is a call for heat, the furnace initiates a normal
start cycle. If the problem has not been corrected, the furnace locks out after three retries.
Associated status/fault codes are CONTINUOUS / RAPID AMBER FLASH (not the same on all
furnace models), 1 RED FLASH, 7 RED FLASHES, 8 RED FLASHES, or 9 RED FLASHES.
a. CONTINUOUS AMBER FLASH: Flame sense current is below .28 microamps. Check and
clean flame sensor. Check for proper gas flow. Verify that current is greater than .28
microamps at flame current test pad.
b. RAPID AMBER FLASH: Flame sense current is below 1.5 microamps for more than 4.25 s
after a successful trial for ignition. Check and clean flame sensor. Check for proper gas flow.
Verify that current is greater than 1.5 microamps at flame current test pad.
c. 1 RED FLASH: This indicates that flame was sensed when there was not a call for heat. The
control will turn on both the inducer motor and supply air blower.
