Whirlpool EDP/EDN - Manual (Page 28)

Page 28 LAARS HEATING SYSTEMS
(2) poor flame sensor signal, (3) inadequate gas
supply, (4) ignitor failure, (5) blocked or
contaminated air source.
1. Poor Combustion: Poor combustion should be
suspected if there is a strong flue gas odor. The
odor may result from either an improper gas/air
ration (high or low CO
2
) or contamination of the
combustion air supply. If an improper gas/air
ratio is suspected refer to “gas valve calibration
(offset adjustment)” on page 25. If
contamination of the air source is suspected refer
to (5) below.
2. Poor flame sensor signal: The boiler control
board will lockout if the flame sensor is
grounded or if the flame signal it receives is less
than 1
mA dc. To check for a grounded sensor,
remove the flame sensor wire (yellow) from the
boiler control board and check for continuity
between the yellow wire terminal and the
combustion chamber bottom pan. If there is
continuity, the flame sensor is grounded. An
alternate way to check for grounding of the
flame sensor is to check the ohms resistance
between the yellow wire terminal and the
combustion chamber bottom pan, using a meter
set for at least 100,000 ohms. The resistance
must be more than 250,000 ohms (some
technicians have been confused by meters which
report infinite resistance with what appears to
them as double zeros; an infinite resistance
reading means there is no grounding of the flame
sensor.) If there is continuity, or the ohms
resistance is less than 250,000 ohms, debris or
moisture in the combustion chamber may be the
cause. To correct, carefully remove the ignitor
and flame sensor assembly. Look for debris on
the assembly where the flame rod exits the
ceramic tube. If debris exists, remove it. If this
area is clean, insert a pencil or other round
object into the flame sensor hole in the bottom
combustion chamber pan and roll it around to
clear any debris that may exist inside the
combustion chamber. Replace the ignitor/flame
sensor assembly, reconnect the yellow wire on
the PCB and start the boiler. If lockout persists,
check the flame signal. To check the flame
signal, disconnect the yellow wire from the
flame sensor, connect a meter, set for microamps
(
mA) DC, between the flame sensor connector
and the yellow wire connector. Start the boiler. If
the meter reading is less than 1.00
mA DC, see
(3) “poor combustion” below. (Check for air
leaks at air inlet to blower.)
3. Inadequate gas supply: Before proceeding,
ensure that the gas supply has not been shutoff
or the LP tank (LP boilers) is not empty. Then,
reset the boiler and observe the operational
cycle. Approximately 20 seconds after the start
of the cycle, the GV LED on the PCB should
light. If it does not, reset the boiler and check for
24 VAC at the plug on the PCB. If the voltage is
less than 20 VAC, and transformer voltage is 24
VAC replace the PCB. If the voltage is correct,
connect a pressure gauge to the offset pressure
port on the gas valve. Reset the boiler and
Figure 29.
Table 4. EBP/EDP 175.
MEASUREMENTS AT HIGH FIRE
NATURAL GAS
% CO 2 9.0 - 9.6
MAX INPUT
175,270
BTU/H
OFFSET
(-0.01 to -.10)
IN W.C.
LP GAS
% CO 2 9.7 - 10.1
MAX INPUT
175,270
BTU/H
OFFSET
(-0.01 to -.10)
IN W.C.
Figure 30. Jumper Wiring for Test and Calibration.