IO-213D
2/04
13
Blower Time Selection
The blower “OFF” timing is field selectable. See below for
the method of changing these times.
BLOWER OFF
TERMINAL
90
120
150
FACTORY SETTING
150 SEC.
OPTIONAL SETTINGS
120 SEC.
90 SEC.
90
120
150
90
120
150
Twinning
• The twin feature allows two furnaces to be connected to a
single control circuit.
• A common ground
must
be provided between the units to
be connected.
• The power supply
must
be obtained from the same buss
bar in the circuit breaker box (each furnace
must
have a
grounded, dedicated circuit).
• The control board
must
be produced by the same
manufacturer.
• It is recommended that common ductwork be used.
• A wire
must
run between the “TWIN” terminals. These
terminals are 3/16".
RATING THE FURNACE
This furnace is shipped from the factory equipped for use
with natural gas. The instructions are for use with natural
gas at altitudes up to 2,000 feet, using a heating value of
1,000 Btu/hr. Should this appliance be converted to L.P.,
refer to the instructions included in the factory authorized
L.P. Conversion Kit
(LPT-01)
. If for use at altitudes in excess
of 2,000 feet refer to the instructions included in the factory
authorized High Altitude Kit
(HA-02).
It is important to check and adjust the input rate of the
furnace to prevent an overfiring situation. Overfiring can cause
premature heat exchanger failure. The input is controlled
by the supply pressure, orifice size, manifold pressure and
heating (calorific) value of the gas.
The supply pressure must be measured with this and all
other gas burning appliances in operation. The supply
pressure must be adjusted to the pressure range stated on
the series and rating plate. Applications for altitudes in
excess of 2,000 feet require an orifice change. The orifices
must be selected using the table below.
The furnace derate
is 4% for each 1,000 feet
above sea level
. This table is
based upon a heating value of approximately 1,000 Btu/ft
3
.
ALTITUDE
NAT. GAS ORIFICE SIZE
0 – 1,999
#45
2,000 – 2,999
#46
3,000 – 3,999
#47
4,000 – 4,999
#47
5,000 – 5,999
#47
6,000 – 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 L.P. 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 are subject to acceptance by the local authorities having
jurisdiction.
WARNING
BEFORE ATTEMPTING ANY SERVICE OR ADJUSTMENTS
- ENSURE 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 on the series and
rating plate.
• After 15 minutes of operation, time the meter with a
stopwatch for 2 revolutions & divide by 2.
• Use the appropriate column in the following table to
determine the furnace input.
• If necessary, adjust the manifold pressure at the gas valve
by removing the regulator cap and turning the adjustment
screw clockwise (
P
) to raise the pressure and
counterclockwise (
Q
) to reduce the pressure. The manifold
pressure must be between 3.2" W.C. and 3.8" W.C. for
natural gas and 9.5"W.C. and 10.5" W.C. for L.P. (a field
conversion is necessary for L.P.). The inability to maintain
the proper pressure range will require reorificing. After
replacing the orifices, repeat the above steps to insure
that the furnace input is adjusted properly.
