Whirlpool EDP/EDN warranty Poor flame sensor signal The boiler control

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 CO2) 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.

MEASUREMENTS AT HIGH FIRE

NATURAL GAS
% CO2	9.0 - 9.6
MAX INPUT	175,270
BTU/H
OFFSET	(-0.01 to -.10)
IN W.C.
	LP GAS
% CO2	9.7 - 10.1
MAX INPUT	175,270
BTU/H

OFFSET

2.	Poor flame sensor signal: The boiler control
	board will lockout if the flame sensor is

IN W.C.

(-0.01 to -.10)

grounded or if the flame signal it receives is less

than 1 ￿A 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

(￿A) DC, between the flame sensor connector

and the yellow wire connector. Start the boiler. If

the meter reading is less than 1.00 ￿A 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

Table 4. EBP/EDP 175.

Figure 29.

Figure 30. Jumper Wiring for Test and Calibration.

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