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SERVICING
S-311 HIGH ALTITUDE APPLICATION (USA)
When these furnaces are installed at high altitude, the ap-
propriate High Altitude Orifice or Pressure Switch Kit must
be applied. This is required due to the natural reduction in
the density of both the gas fuel and combustion air as alti-
tude increases. The High Altitude Orifice Kit will provide the
proper design certified input rate within the specified alti-
tude range.
High Altitude Orifice or Pressure Switch Kits are purchased
according to the installation altitude and usage of either natu-
ral or propane gas. Refer to the Technical Manual or prod-
uct Specification Sheet for a tabular listing of appropriate
altitude ranges and corresponding manufacturer's high alti-
tude (Natural or Propane Gas) orifice or pressure switch
kits.
Do not derate the furnace by adjusting the manifold pres-
sure to a lower pressure than specified on the furnace rating
plate. The combination of the lower air density and a lower
manifold pressure will prohibit the burner orifice from draw-
ing the proper amount of air into the burner. This may cause
incomplete combustion, flashback, and possible yellow tip-
ping.
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 th e 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:
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: A poor earth ground, floating ground, or high resis-
tance neutral line will significantly shorten the life of the
Sillicon Nitride (SiNi) igniter used in Amana
and 90% furnaces.
124
content of the derated
3
®
brand 80%
This section discusses various integrated ignition boards
used on models listed in this manual. You will be guided
though some common diagnostic procedures.
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.
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
10 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
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 furnace
failures to help in troubleshooting. A flashing red or green
diagnostic indicator light on the control flashes a code for
any detected failures.
When the control is powered up normally the light will be on
continuously. 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 diag-
nostic indicator light. Refer to the Abnormal Operation sec-
tion in the Sequence of Operation section of this manual for
more detail on failure codes.
The indicator light may be viewed by looking through the
sight glass in the blower compartment door. If the blower
compartment door is removed, failure to hold the door switch
closed while removing the blower compartment door will re-
sult in the loss of the stored failure code. In most cases
recycling the ignition control will result in the same failure
code originally displayed.
WARNING
D
ISCONNECT POWER
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