IO-151
14
6,000
#48
7,000
#48
The input to the furnace must be checked AFTER reorificing.
For altitudes above 7,000 feet refer to appropriate section of the National Fuel Gas Code, ANSI
Z223.1. To calculate the input of the furnace for installations in altitudes over 2,000 feet, use the
following formula;
CORRECTED INPUT = SERIES & RATING PLATE INPUT - (ALTITUDE X .04) X SERIES &
RATING PLATE INPUT / 1000
EXAMPLE:
Corrected input for a 100,000 Btu/hr. appliance installed at an altitude of 6.000 ft. utilizing natural
gas with a heating value of 1,000 But/ft
3
is determined by-
Corrected Input = 100,000 - (6,000 X .04) X (100,000 / 1,000)
Corrected Input = 100,000 - (240 X 100)
Corrected Input = 100,000 - 24,000
Corrected Input = 76,000
Using the orifices sized as shown in the table for 6,000 feet (#48), a meter time of 48.0 seconds is
measured. The actual firing rate of the furnace is
Input = 1,000 (heating value of the gas) X 3600 (constant) / 48.0 (meter time for 1 ft
3
of gas)
Input = 3,600,000 / 48.0
Input = 76,000 Btu/hr
In Canada, the series and rating plate input for the furnace apply to installations up to 2,000 feet
(610m) above sea level. Kit HA-02 for natural and LP gases is required to convert furnaces from
elevations of 2,000 to 4,500 feet (610m to 1,370m). Canadian certification applies to the
installations of up to 4,500 feet above sea level. Installations above 4,500 feet is subject to
acceptance by the local authorities having jurisdiction.
WARNING
BEFORE ATTEMPTING ANY SERVICE OR ADJUSTMENTS - INSURE THAT THE GAS AND
ELECTRICAL SUPPLIES ARE “OFF”.
TIMING THE GAS METER
Use the following method to determine the firing rate of the furnace. The supply pressure tap
should be located on the field installed piping or gas shut-off valve. The manifold pressure tap is
located on the combination gas valve in the furnace and labeled “OUTLET PRESSURE TAP”.
•
Install a manometer graduated in tenths of an inch of water column on the supply pressure tap
of the gas supply pipe.
•
Remove plug at the “Manifold” pressure tap on the gas valve and install a second manometer.
•
Determine the size of gas meter used.
•
Shut off all other gas fired appliances with the exception of the pilots.
•
Place furnace in operation.
•
Check the supply pressure as shown the on series and rating plate.
•
After 15 minutes of operation, time the meter with a stop watch for 2 revolutions & divide by 2.
•
Use the appropriate column to determine the furnace input.
