650.67-N2V
035-15881-402 REV. A (1199)
14
Unitary Products Group
HOW TO DETERMINE GAS INPUT RATE
Where gas is metered, the input rate may be determined by
the following method:
Contact the gas supplier, public utility company or LP (pro-
pane) gas distributor to obtain the calorific gas value of the
gas being used. When checking the gas input rate, any other
gas burning appliances connected to the same meter should
be completely off. The furnace should be allowed to operate
for 5 minutes before attempting to check the gas input rate.
To check flow rate, observe the one cubic foot dial on the gas
meter and determine the number of seconds required for the
dial hand to complete one revolution (seconds to flow one
cubic foot.)
To determine the number of seconds per cubic foot that is
necessary to achieve the correct input rate, use the following
formula: GAS VALUE X 3600
!
DESIRED INPUT = SEC-
ONDS NEEDED.
Example: 1000 BTU gas, furnace input 100,000 BTUH Sec-
onds for one cubic foot = 1000 X 3600
!
100,000 = 36 sec-
onds.
If, when clocking the meter, the one cubic foot dial makes a
complete revolution in less time than was calculated that it
should, the furnace is overfired and should be derated. If it
takes more time for the meter to make one revolution than
was calculated, the furnace is underfired.
The orifice size must be changed to correct an overfired or
underfired condition. If it is determined that different orifices
are needed, please contact your distributor for assistance in
selecting the correct replacement.
CONVERSION INSTRUCTIONS
MODELS WITH CONVERTIBLE REGULATOR (SEE FIG-
URE 9):
These furnaces are design certified for use with
either Natural or LP gas, and may be converted from one gas
to the other. Parts necessary for conversion are included with
the furnace. Instructions for making the conversion are
printed on a label inside the burner compartment access
panel, and on the rating plate.
MINOR INPUT ADJUSTMENT
The input may be adjusted slightly by adjusting the pressure
regulator setting in the gas valve in order to change the man-
ifold pressure.
MODELS WITH CONVERTIBLE REGULATOR (SEE FIG-
URE 9) USING NATURAL GAS:
Remove the pressure regu-
lator converter with a 7/16" open end or boxed end wrench,
exposing the adjusting screw. Turn the screw counter-clock-
wise to decrease pressure, clockwise to increase pressure.
Remove the convertible regulator top portion, paying close
attention to install as removed, i.e., the arrow for the side
marked "NAT." must face the body of the valve.
USING LP (PROPANE) GAS:
Remove the plastic dust cover
from the pressure regulator convertor. Using an Allen type
wrench, with the converter screwed snugly into the valve,
turn the set screw counter-clockwise to decrease pressure,
clockwise to increase pressure.
IMPORTANT -
In no case should the final manifold pres-
sure vary more than ± .3" W.C. from the specified regulator
pressure settings (3.5" for Natural Gas and 10" for LP [Pro-
pane] Gas.)
MEASURING AIR TEMPERATURE RISE
For proper furnace operation, the air temperature rise must
be within the range shown on the furnace rating plate.
HIGH ALTITUDE GAS ORIFICES
ALTITUDE ABOVE SEA LEVEL IN FEET
GAS TYPE
0-2,000
2,000-4,500
4,500-8,000
8,000-9,000
9,000-10,000
NATURAL GAS
#42
#43
#44
#45
#46
.093
.089
.086
.082
.081
LP GAS
#54
#55
#55
#56
#56
.055
.052
.052
.046
.046
Never attempt to modify this furnace, fire,
explosion, or asphyxiation may result.
If mal-
function is apparent, contact qualified service
agency and/or gas utility for assistance.
Operating the furnace outside of the proper air
temperature rise range may cause poor heating
performance and shorter heat exchanger life.
