Troubleshooting Guide - L.B. White AW250 Owner's Manual And Instructions

READ THIS ENTIRE SECTION BEFORE
BEGINNING TO TROUBLESHOOT PROBLEMS.
Electrical Shock and Burn Hazard
■
Troubleshooting this system may require operating the
unit with line voltage present and gas on. Use extreme
caution when working on the heater.
■
Failure to follow this warning may result in property
damage, personal injury or death.
The troubleshooting flow charts on the following pages
provide systematic procedures for isolating equipment
problems. The charts are intended for use by a QUALIFIED
GAS HEATER SERVICE PERSON. DO NOT SERVICE THESE
HEATERS UNLESS YOU HAVE BEEN PROPERLY TRAINED.
TEST EQUIPMENT REQUIRED
The following pieces of test equipment will be required to
troubleshoot this system with minimal time and effort.
• Digital Multimeter - for measuring AC and DC voltage and
resistance.
• Microamp Diagnostic Kit - (L. B. White Part No. 500-
08507) When used with a standard digital multimeter,
this kit allows testing of the flame sensor on direct
ignition systems.
• Low Pressure Gauge - for checking inlet and manifold
pressures at the gas control valve against dataplate
rating.
INITIAL PREPARATION
■
Visually inspect equipment for apparent damage.
■
Check all hoses for abrasion and wear. Replace any that are
suspect.
■
Make sure heater is properly installed and meets minimum
clearances to nearest combustible materials. (Refer to
dataplate on heater.)
■
Check all wiring for loose connections and worn insulation.
Refer to the system operation sequence in this section to
gain an understanding as to how the equipment operates
during a call for heat. Understanding the operation
sequence of the ignition module and related components
is essential as it will relate directly to problem solving
provided by the flow charts.
The ignition control module is self-diagnostic. The red
light on the module will flash a specific pattern depending
upon the problem which is diagnosed. To effectively use
the flow charts, you must first identify what the problem is
by the flashing pattern of the L.E.D. (light emitting diode)
diagnostic light. If the light is flashing, the flash pattern
will be followed by a pause and then a repeat of the flash
pattern until the problem is corrected. Refer to the tables
below to identify what page to refer to when
troubleshooting any problems.
The L.E.D. will only be on when the selector switch is
positioned to "Heat" and the thermostat is set above room
temperature. The L.E.D. will not be on when the selector
switch is positioned to "Vent".
WARNING

Troubleshooting Guide

Heating Mode Problems
L.E.D. Diagnostic light not on during a call for heat . . .19
L.E.D. diagnostic light flashing:
A. Rapid Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
B. Long Flash (2 seconds on - 2 seconds off) . . . . .20
C. One Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
D. Two Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
E. Three Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
F. Four Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
G. Five Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
H. Six Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Ventilation Mode Problems
A. Motor Does Not Run . . . . . . . . . . . . . . . . . . . . . . .24
B. Motor "Hums", Does Not Run . . . . . . . . . . . . . . . .24
Components should be replaced only after each step has
been completed and replacement is suggested in the flow
chart.
DIRECT IGNITION OPERATION SEQUENCE:
(Heating Mode)
— Line Voltage is Sent from Selector Switch to Transformer
— 24 V.A.C. is sent from Transformer to the Thermostat
— A call for Heat Occurs
— 24 V.A.C. is sent from Thermostat to Ignition Control Module
— Red Light on Ignition Module Begins to Glow
— Ignition Control Module Performs an Internal Safe Start Check
-- Internal Components are Tested
-- Voltage is sent to Flame Sensor from Control Module
to Start Flame Proving Process
-- Air Flow Circuit is Checked
— Ignition Control Module Begins Safety Lockout Timing
— Ignition Control Module Starts Fan Motor for Prepurge
-- Air Flow Switch is Checked for Proper Operation
-- Module Stops the Fan Motor
— Ignition Control Module Powers the Igniter
— Ignition Control Module Restarts the Fan Motor (after igniter
warm-up)
-- Air Flow Switch Closes
-- Gas Control Valve Opens
— Ignition Occurs
-- Igniter stays "Powered-up" for 6 seconds after Ignition
-- Flame Proving occurs (in 6 seconds)
-- Igniter Shuts Off
-- Gas Valve Stays Open
— Room Warms to Desired Temperature
-- Thermostat is Satisfied
-- Heater Shuts Down
— Process Starts Again on Call for Heat
IGNITION FAILURE SEQUENCE:
— First Trial for Ignition Takes Approximately 30 Seconds
— Two More Trials for Ignition will Occur
-- Second Trial Follows Immediately if First Trial Fails
-- Module Star ts a 15 Minute " Wait" Period to Allow
Ignition Interruption to Pass
-- Third and Final Trial Occurs Af ter 15 Minute Wait
Period
— If Ignition Control Module Does Not Prove Flame After Third
Trial, the Module Goes into Safety Lockout (3 Flash Pattern)
-- Igniter Shuts Down
-- Fan Motor Stops
-- Gas Valve Closes
— To Manually Reset the Ignition System
-- Unplug the Heater and Plug it back in
-- OR --
Turn Thermostat to "Off" or "No Heat" and Then Back
to Above Room Temperature
-- OR --
Move the Heat/Vent Selector Switch to "Of f" and
Then Back to "Heat".
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