Service Manual

SERVICING
85
S-311 HIGH ALTITUDE APPLICATION (USA)
The furnace as shipped requires no change to run be-
tween 0 - 4500 feet. Do not attempt to increase the firing
rate by changing orifices or increasing the manifold pres-
sure below 4500 feet. This can cause poor combustion
and equipment failure. High altitude installations above 4500
feet may require both a pressure switch and an orifice
change. These changes are necessary to compensate for
the natural reduction in the density of both the gas fuel and
the combustion air at higher altitude.
For installations above 4500 feet, please refer to your dis-
tributor for required kit(s). Contact the distributor for a tabu-
lar listing of appropriate manufacturer’s kits for propane gas
and/or high altitude installations. The indicated kits must
be used to insure safe and proper furnace operation. 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 orifice size must
be determined based on the BTU/ft
3
content of the derated
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:
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
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.
D
ISCONNECT POWER
BEFORE PERFORMING SERVICE LISTED BELOW.
WARNING
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 10 ohms.
The ignition control is a combination electronic and elec-
tromechanical device and is not field repairable. Complete
unit must be replaced.
LINE VOLTAGE NOW PRESENT
WARNING
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. The control utilizes a dual, 7-seg-
ment LED display to indicate diagnostic codes.
When the control is powered up normally the light will be on
continuously. The display will indicate "ON" when pow-
ered 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 Abnor-
mal Operation section in the Sequence of Operation sec-
tion of this manual for more detail on failure codes.
PCBKF103 / PCBKF104 / PCBKF105 Control Board
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.