39
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)
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 new gas valve is
required. The new gas valve is
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.
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.
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, Remove
the gas valve.
4. Reassemble in reverse order. In
LP applications, use the new gas
valve provided in the LP
conversion kit.
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.
Altitude BTU Input (per burner) 15000 Orifice Size
0 to 2000 ft. 15000 1.15 mm (factory)
2001 to 3000 13200 1.15 mm
3001 to 4000 12600 1.10 mm
4001 to 5000 12000 #58
5001 to 6000 11400 #59
6001 to 7000 10800 #60
7001 to 8001 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.
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.
CAUTION
!
CAUTION
!
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