FURNACE RESTART
With furnace operating, set thermostat below room temperature
and observe that furnace goes off. Set thermostat above room
temperature and observe that furnace restarts.
Step 5—Adjustments
SET GAS INPUT RATE
Furnace gas input rate on rating plate is for installations at altitudes
up to 2000 ft.
In the U.S.A., the input ratings for altitudes above 2000 ft must be
reduced by 2 percent for each 1000 ft above sea level.
In Canada, the input ratings must be derated by 5 percent for
altitudes of 2001 ft to 4500 ft above sea level.
Adjust manifold pressure to obtain input rate.
Furnace input rate must be within ± 2 percent of input on furnace
rating plate adjusted for altitude.
1. Determine Natural Gas Orifice Size And Manifold Pressure
For Correct Input.
TABLE 10—MODEL 58MTA ORIFICE SIZE AND HIGH/LOW-HEAT MANIFOLD PRESSURES
FOR CORRECT INPUTS
FOR USE WITH 060 THROUGH 120 SIZE FURNACES ONLY
(TABULATED DATA BASED ON 20,000/13,000 BTUH PER BURNER, DERATED 2 PERCENT FOR EACH 1000
FT ABOVE SEA LEVEL)*
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
0.66
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
U.S.A.
and
Canada
0
to
2000
0%
derate
850
43
3.7/1.5
43
3.8/1.6
42
3.2/1.4
42
3.3/1.4
42
3.4/1.4
875
43
3.5/1.5
43
3.6/1.5
43
3.7/1.6
43
3.8/12.6
42
3.2/1.4
900
44
3.7/1.6
43
3.4/1.4
43
3.5/1.5
43
3.6/1.5
43
3.7/1.6
925
44
3.5/1.5
44
3.7/1.6
44
3.8/1.6
43
3.4/1.4
43
3.5/1.5
950
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
44
3.7/1.6
44
3.8/1.6
975
44
3.2/1.3
44
3.3/1.4
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
1000
45
3.7/1.6
45
3.8/1.6
44
3.2/1.4
44
3.4/1.4
44
3.5/1.5
1025
45
3.5/1.5
45
3.6/1.5
45
3.7/1.6
44
3.2/1.3
44
3.3/1.4
1050
45
3.3/1.4
45
3.4/1.5
45
3.6/1.5
45
3.7/1.6
45
3.8/1.6
1075
45
3.2/1.3
45
3.3/1.4
45
3.4/1.4
45
3.5/1.5
45
3.6/1.5
1100
47
3.6/1.5
47
3.7/1.6
45
3.2/1.4
45
3.4/1.4
45
3.5/1.5
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
0.66
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
U.S.A.
and
Canada
U.S.
Altitudes
2001
to
3000
or
Canada
Altitudes
2001
to
4500
5%
derate
775
43
3.8/1.6
42
3.2/1.4
42
3.3/1.4
42
3.4/1.4
42
3.5/1.5
800
43
3.5/1.5
43
3.7/1.5
43
3.8/1.6
42
3.2/1.4
42
3.3/1.4
825
44
3.8/1.6
43
3.4/1.5
43
3.6/1.5
43
3.7/1.5
43
3.8/1.6
850
44
3.6/1.5
44
3.7/1.6
44
3.8/1.6
43
3.5/1.5
43
3.6/1.5
875
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
44
3.7/1.6
43
3.4/1.4
900
44
3.2/1.4
44
3.3/1.4
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
925
45
3.7/1.5
45
3.8/1.6
44
3.2/1.4
44
3.3/1.4
44
3.4/1.5
950
45
3.5/1.5
45
3.6/1.5
45
3.7/1.6
45
3.8/1.6
44
3.3/1.4
975
45
3.3/1.4
45
3.4/1.4
45
3.5/1.5
45
3.6/1.5
45
3.8/1.6
1000
47
3.7/1.6
45
3.2/1.4
45
3.4/1.4
45
3.5/1.5
45
3.6/1.5
1025
47
3.6/1.5
47
3.7/1.6
45
3.2/1.3
45
3.3/1.4
45
3.4/1.4
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
0.66
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
U.S.A.
Only
3001
to
4000
7%
derate
750
43
3.7/1.6
43
3.8/1.6
42
3.3/1.4
42
3.4/1.4
42
3.5/1.5
775
43
3.5/1.5
43
3.6/1.5
43
3.7/1.6
43
3.8/1.6
42
3.2/1.4
800
44
3.7/1.6
43
3.4/1.4
43
3.5/1.5
43
3.6/1.5
43
3.7/1.6
825
44
3.5/1.5
44
3.6/1.5
44
3.8/1.6
43
3.4/1.4
43
3.5/1.5
850
44
3.3/1.4
44
3.4/1.4
44
3.5/1.5
44
3.7/1.5
44
3.8/1.6
875
45
3.8/1.6
44
3.2/1.4
44
3.3/1.4
44
3.5/1.5
44
3.6/1.5
900
45
3.6/1.5
45
3.7/1.6
45
3.8/1.6
44
3.3/1.4
44
3.4/1.4
925
45
3.4/1.4
45
3.5/1.5
45
3.6/1.5
45
3.7/1.6
44
3.2/1.3
950
45
3.2/1.4
45
3.3/1.4
45
3.4/1.5
45
3.5/1.5
45
3.7/1.5
975
47
3.6/1.5
45
3.2/1.3
45
3.3/1.4
45
3.4/1.4
45
3.5/1.5
1000
47
3.5/1.5
47
3.6/1.5
45
3.7/1.6
45
3.2/1.4
45
3.3/1.4
* Orifice numbers shown in shading are factory installed.
NOTE: Percents of derate are based on midpoints of U.S. altitude ranges.
44
