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LP CONVERSION
IMPORTANT: LP gas from trucks
used to transport liquid-based
fertilizers can contain chemicals that
will damage the furnace. Verify that
your gas supplier does not use the
same truck to transport materials
other than LP.
For LP conversion, a spring kit is
required. The springs are included in
the LP kit. The correct LP orifices
should be selected based on the
altitude of the installation (see chart
below). Orifices included in the kit are
for sea level to 2000 ft. (1.15mm) and
3000 to 4000 ft. (1.10mm) The LP
Gas Valve Kit is FP19. Orifices for
elevations 4000 ft. and above must
be ordered. Refer to Table 7.
CAUTION
ELEVATIONS ABOVE 2000 FT
REQUIRE THAT THE FURNACE
INPUT RATING BE ADJUSTED
AND THAT THE SIZE OF THE
BURNER ORIFICES BE RE-
CALCULATED BASED ON
ELEVATION AND GAS HEATING
VALUE. THE BURNER ORIFICES
MAY (OR MAY NOT) NEED TO BE
CHANGED. SEE THE SECTION
TITLED "HIGH ALTITUDE
INSTALLATIONS" OF THIS BOOK
FOR INSTRUCTIONS.
NOTE: Furnace conversion to LP gas
must be performed by a qualified
installer, service agency or the gas
supplier.
TABLE 7
IMPORTANT: 90+ MODELS ONLY. DO NOT USE THIS CHART
FOR ANY 80 PLUS MODELS.
LP GAS ORIFICE DRILL SIZE (4% PER 1000 FT DE-RATE)
Altitude
0 to 2000 ft.
2001 to 3000
3001 to 4000
4001 to 5000
5001 to 6000
6001 to 7000
7001 to 8001
To change the gas valve and orifice
spuds for either conversion to LP or for
elevation:
1. Shut off the manual main gas valve
and remove the gas manifold.
2. Replace the orifice spuds.
3. For LP conversion ONLY, replace
the springs per instructions
provided.
4. Reassemble in reverse order. In
LP applications, use the new gas
valve provided in the LP
conversion kit. Be sure to check
manifold pressure and set rate.
5. Attach the notice label alerting the
next service technician that the
furnace has been converted to LP
gas.
6. Turn the gas supply back on and
check for proper operation, leaks
and manifold pressure. See
Figures 37 and 39.
NOTE: Orifices in the kit are sized for a
heating value of 2500 BTU per cubic ft.
for LP.
ORIFICE ORDERING
INFORMATION
Orifice sizes are selected by adding the
2-digit drill size required in the orifice
part number. Drill sizes available are 39
through 64; metric sizes available
1.10mm (-90) and 1.15mm (-91):
Orifice Part Number 62-22175-(drill
size)
Example 1:
# 60 drill size orifice required
Part # 62-22175-60
Example 2:
1.15mm drill size orifice required
Part # 62-22175-91
NOTE: Do not plug or drill out orifices.
BTU Input (per burner) 15000 Orifice Size
15000
1.15 mm (factory)
13200
1.15 mm
12600
1.10 mm*
12000
#58*
11400
#59**
10800
#60
10200
#62
SETTING GAS PRESSURE
The maximum gas supply pressure
to the furnace should be 10.5" w.c.
natural gas, or 13" w.c. LP gas. The
minimum supply gas pressure to the
gas valve should be 5" w.c. natural
gas or 11" w.c. LP gas. A properly
calibrated U-Tube manometer is
required for accurate gas pressure
measurements.
CAUTION
ELEVATIONS ABOVE 2000 FT
REQUIRE THAT THE FURNACE
INPUT RATING BE ADJUSTED AND
THAT THE SIZE OF THE BURNER
ORIFICES BE RE-CALCULATED
BASED ON ELEVATION AND GAS
HEATING VALUE. THE BURNER
ORIFICES MAY (OR MAY NOT)
NEED TO BE CHANGED. SEE THE
SECTION TITLED "HIGH ALTITUDE
INSTALLATIONS" OF THIS BOOK
FOR INSTRUCTIONS.
Supply Gas Pressure Measure-
ment. A line pressure tap is on the
input side of the gas valve. See Figure
37.
1. With gas shut off to the furnace at
the manual gas stop outside the
unit, remove the input pressure
tap plug.
2. Connect a U-Tube manometer to
the pressure tap.
3. Turn on the gas supply and
operate the furnace and all other
gas-fired units on the same gas
line as the furnace.
4. Note or adjust the line gas
pressure to give:
A. 5" - 10.5" w.c. for natural gas.
B. 11" - 13" w.c. for LP gas.
5. Shut off the gas at the manual
gas stop and remove the
U-Tube manometer.
6. Replace the pressure tap plug
before turning on the gas. Turn
on gas and check for leaks.
If the supply gas line pressure is
above these ranges, install an in-line
gas regulator to the furnace for natural
gas units. With LP gas, have the LP
supplier reduce the line pressure at
the regulator.
If supply gas line pressure is below
these ranges, either remove any
restrictions in the gas supply piping or
enlarge the gas pipe. See Tables 6
and 8. With LP gas, have the LP
supplier adjust the line pressure at the
regulator.
Manifold Gas Pressure
Measurement. Natural gas
manifold pressure should
39
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