Checking For Delayed Ignition; Checking Integrated Ignition Control Boards - Intertek ACVC96 Service Instructions Manual

SERVICING
In some areas the gas supplier may artificially derate the
gas in an effort to compensate for the effects of altitude. If
the gas is artificially derated the appropriate orfice size must
be determined based on the BTU/ft
gas and the altitude. Refer to the National Fuel Gas Code,
NFPA 54/ANSI Z223.1, and information provided by the gas
supplier to determine the proper orifice size.
S-312 CHECKING FOR DELAYED IGNITION
Delayed ignition is a delay in lighting a combustible mixture
of gas and air which has accumulated in the combustion
chamber.
When the mixture does ignite, it may explode and/or rollout
causing burning in the burner venturi.
If delayed ignition should occur, the following should be
checked. Furnace design makes this extremely unlikely
unless safety controls have been by-passed or tampered
with. Never by-pass or alter furnace controls.
1. Improper gas pressure - adjust to proper pressure (See
S-307 CHECKING GAS PRESSURE).
2. Improper burner positioning - burners should be in locat-
ing slots, level front to rear and left to right.
3. Carry over (lighter tube or cross lighter) obstructed - clean.
4. Main burner orifice(s) deformed, or out of alignment to
burner - replace.
S-313 CHECKING INTEGRATED IGNITION
CONTROL BOARDS
NOTE: Failure to earth ground the furnace, reversing the
neutral and hot wire connection to the line (polarity), or a
high resistance connection in the neutral line may cause
the control to lockout due to failure to sense flame.
WARNING
T
O AVOID THE RISK OF ELECTRICAL SHOCK, WIRING TO THE UNIT
MUST BE PROPERLY POLARIZED AND GROUNDED.
BEFORE PERFORMING SERVICE LISTED BELOW.
The ground wire must run from the furnace all the way back
to the electrical panel. Proper grounding can be confirmed
by disconnecting the electrical power and measuring resis-
tance between the neutral (white) connection and the burner
closest to the flame sensor. Resistance should be less than
2 ohms.
The ignition control is a combination electronic and electro-
mechanical device and is not field repairable. Complete unit
must be replaced.
WARNING
L
INE VOLTAGE NOW PRESENT
3
content of the derated
D
ISCONNECT POWER
These tests must be completed within a given time frame
due to the operation of the ignition control. The trial for igni-
tion period is 4 seconds.
The ignition control is capable of diagnosing many furnace
failures to help in troubleshooting. The control utilizes a
dual, 7-segment LED display to indicate diagnostic codes.
When the control is powered up normally the light will be on
continuously. The display wil indicate "ON" when powered
and in standby mode. This can be used to test for 120 volts
and 24 volts to the control since both must be present for
the light to be on. If this step fails, check for 120 volts to the
control and check the transformer and its associated wiring.
If this step is successful give the control a call for heat and
wait five (5) seconds or until the furnace goes into lockout. If
the control detects a failure it will now be shown on the
diagnostic indicator light/display. Refer to the Abnormal Op-
eration section in the Sequence of Operation section of this
manual for more detail on failure codes.
1. Check for 120 volts from Line 1 (Hot) to Line 2 (Neutral)
at the ignition control. No voltage, check the door switch
connections and wire harness for continuity.
2. With the thermostat calling for heat, check for 24 volts
from W1 to C terminal on the ignition control. No volt-
age. Check transformer, room thermostat, and wiring.
If you have 24 volts coming off the transformer but re-
ceive approximately 13 volts on the terminal board be-
tween (C) and (R), check for blown fuse.
3. Check for 120 volts to the induced draft blower (low-stage)
by measuring voltage between Pin 3 and Pin 4 (on the 5-
pin connector) located on circuit board. No voltage, check
for loose connection in the 5-pin connector or replace
ignition control.
Check for 120 volts to the induced draft blower (high-
stage) by measuring voltage between Pin 2 and Pin 4
(on the 5-pin connector) located on circuit board. No volt-
age, check for loose connection in the 5-pin connector,
no call for high stage heat or replace ignition control.
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