High Altitude Application (Usa); Checking For Delayed Ignition; Checking Integrated Ignition Control Boards - Goodman AMH8 Service Instructions Manual

SERVICING
Induced Draft Blower
Pressure Switch
1/4" Tee
ID Blower Pressure Switch
Negative Pressure Measurement
(80% Upflow Single-Stage Furnace Shown,
Counterflow Similar)
S-311 HIGH ALTITUDE APPLICATION (USA)
Check your furnace rated altitude on the furnace rating
plate. Do not attempt to increase the firing rate by chang-
ing orifices or increasing the manifold pressure below rated
altitude. This can causepoor combustion and equipment
failure. High altitude installations above rated altitude may
require both a pressure switch and an orifice change. These
changes are necessary to compensate for the natural re-
duction in the density of both the gasfuel and the combus-
tion air at higher altitude.
For installations above rated altitude, please refer to your
distributor for required kit(s). Contact the distributor for a
tabular listing of appropriate manufacturer's kits for pro-
pane gas and/or high altitude installations. The indicated
kits must be used to insure safe and proper furnace op-
eration. All conversions must be performed by a qualified
installer, or service agency.
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
derated gas and the altitude. Refer to the National Fuel
Gas Code, NFPA 54/ANSI Z223.1, and information pro-
vided by the gas supplier to determine the proper orifice
size.
60
Pressure Switch
Hose
Inclined Manometer
Hose to Induced
Draft Blower Tap
3
content of the
S-312 CHECKING FOR DELAYED IGNITION
Delayed ignition is a delay in lighting a combustible mix-
ture of gas and air which has accumulated in the combus-
tion chamber.
Furnace design makes this extremely unlikely unless safety
controls have been by-passed or tampered with. Never
by-pass or alter furnace controls.
If delayed ignition should occur, the following should be
checked:
1. Improper gas pressure - adjust to proper pressure (See
S-307 CHECKING GAS PRESSURE).
2. Improper burner positioning - burners should be in
locating 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 CON-
TROL 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 con-
firmed by disconnecting the electrical power and measur-
ing resistance 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 elec-
tromechanical device and is not field repairable. Com-
plete unit must be replaced.
WARNING
L
INE VOLTAGE NOW PRESENT
These tests must be completed within a given time frame
due to the operation of the ignition control.
The ignition control is capable of diagnosing many fur-
nace failures to help in troubleshooting. The trial for igni-
tion period is 4 seconds.
1. Check for 120 volts from Line 1 (Hot) to Line 2 (Neu-
tral) at the ignition control. No voltage, check the door
switch connections and wire harness for continuity.
D
ISCONNECT POWER