45
Table 12 -- Orifice Size and Manifold Pressure (In. wc) for Gas Input Rate (Con’t.)
(Tabulated Data Based on 22,000 Btuh High--Heat/14,500 Btuh for Low-- Heat per Burner, Derated 4 Percent for Each 1000 Ft.
Above Sea Level)
ALTITUDE
RANGE
FT. (M)
AVG. GAS
HEAT VALUE
AT ALTITUDE
(BTUH/CU FT.)
SPECIFIC GRAVITY OF NATURAL GAS
0.58 0.60 0.62 0.64
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
USA
Only
5001 to
6000
(1524
to
1829)
725 43 3.4/1.5 43 3.5/1.5 43 3.6/1.6 43 3.7/1.6
750 43 3.2/1.4 43 3.3/1.4 43 3.4/1.5 43 3.5/1.5
775 44 3.4/1.5 44 3.5/1.5 43 3.2/1.4 43 3.3/1.4
800 44 3.2/1.4 44 3.3/1.4 44 3.4/1.5 44 3.5/1.5
825 46 3.8/1.7 45 3.8/1.6 44 3.2/1.4 44 3.3/1.4
850 46 3.6/1.6 46 3.7/1.6 46 3.8/1.7 45 3.8/1.6
875 47 3.8/1.7 46 3.5/1.5 46 3.6/1.6 46 3.7/1.6
900 47 3.6/1.6 47 3.8/1.6 46 3.4/1.5 46 3.5/1.5
ALTITUDE
RANGE
FT. (M)
AVG. GAS
HEAT VALUE
AT ALTITUDE
(BTUH/CU FT.)
SPECIFIC GRAVITY OF NATURAL GAS
0.58 0.60 0.62 0.64
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
USA
Only
6001 to
7000
(1829
to
2134)
675 43 3.4/1.5 43 3.5/1.5 43 3.6/1.6 43 3.7/1.6
700 44 3.6/1.6 43 3.3/1.4 43 3.4/1.5 43 3.5/1.5
725 44 3.4/1.5 44 3.5/1.5 44 3.6/1.6 43 3.2/1.4
750 45 3.8/1.7 44 3.3/1.4 44 3.4/1.5 44 3.5/1.5
775 46 3.7/1.6 45 3.7/1.6 45 3.8/1.7 44 3.2/1.4
800 46 3.5/1.5 46 3.6/1.6 46 3.8/1.6 45 3.7/1.6
825 47 3.7/1.6 46 3.4/1.5 46 3.5/1.5 46 3.6/1.6
850 47 3.5/1.5 47 3.6/1.6 47 3.8/1.6 46 3.4/1.5
ALTITUDE
RANGE
FT. (M)
AVG. GAS
HEAT VALUE
AT ALTITUDE
(BTUH/CU FT.)
SPECIFIC GRAVITY OF NATURAL GAS
0.58 0.60 0.62 0.64
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
USA
Only
7001 to
8000
(2134
to
2438)
650 44 3.6/1.6 43 3.2/1.4 43 3.4/1.5 43 3.5/1.5
675 44 3.3/1.5 44 3.5/1.5 44 3.6/1.6 43 3.2/1.4
700 45 3.8/1.6 44 3.2/1.4 44 3.3/1.4 44 3.4/1.5
725 46 3.7/1.6 46 3.8/1.7 45 3.7/1.6 44 3.2/1.4
750 46 3.4/1.5 46 3.6/1.5 46 3.7/1.6 46 3.8/1.6
775 47 3.6/1.6 47 3.8/1.6 46 3.4/1.5 46 3.6/1.5
800 47 3.4/1.5 47 3.5/1.5 47 3.7/1.6 47 3.8/1.6
825 48 3.7/1.6 48 3.8/1.6 47 3.4/1.5 47 3.6/1.5
ALTITUDE
RANGE
FT. (M)
AVG. GAS
HEAT VALUE
AT ALTITUDE
(BTUH/CU FT.)
SPECIFIC GRAVITY OF NATURAL GAS
0.58 0.60 0.62 0.64
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
USA
Only
8001 to
9000
(2438
to
2743)
625 44 3.3/1.5 44 3.5/1.5 44 3.6/1.6 43 3.2/1.4
650 45 3.7/1.6 44 3.2/1.4 44 3.3/1.4 44 3.4/1.5
675 46 3.6/1.6 46 3.8/1.6 45 3.7/1.6 45 3.8/1.7
700 47 3.8/1.7 46 3.5/1.5 46 3.6/1.6 46 3.7/1.6
725 47 3.6/1.6 47 3.7/1.6 47 3.8/1.7 46 3.5/1.5
750 48 3.8/1.7 47 3.5/1.5 47 3.6/1.6 47 3.7/1.6
775 48 3.6/1.5 48 3.7/1.6 48 3.8/1.7 47 3.5/1.5
USA
Only
9001 to
10,000
2743 to
3048)
600 45 3.7/1.6 45 3.8/1.7 44 3.3/1.4 44 3.4/1.5
625 46 3.6/1.6 46 3.7/1.6 46 3.8/1.7 45 3.8/1.6
650 47 3.8/1.6 46 3.4/1.5 46 3.6/1.5 46 3.7/1.6
675 47 3.5/1.5 47 3.6/1.6 47 3.7/1.6 46 3.4/1.5
700 48 3.7/1.6 48 3.8/1.7 47 3.5/1.5 47 3.6/1.6
725 48 3.5/1.5 48 3.6/1.6 48 3.7/1.6 48 3.8/1.7
* Orifice numbers 43 are factory installed
Check Safety Controls
The flame sensor, gas valve, and pressure switch were all checked
in the Start--up procedure section as part of normal operation.
1. Check Main Limit Switch
This control shuts off combustion system and energizes
air--circulating blower motor, if furnace overheats. By us-
ing this method to check limit control, it can be established
that limit is functioning properly and will operate if there
is a restricted return-- air supply or motor failure. If limit
control does not function during this test, cause must be
determined and corrected.
a. Run furnace for at least 5 minutes.
b. Gradually block off return air with a piece of card-
board or sheet metal until the limit trips.
c. Unblock return air to permit normal circulation.
d. Burners will re--light when furnace cools down.
2. Check draft safeguard switch. The purpose of this control
is to cause the safe shutdown of the furnace during certain
blocked vent conditions.
a. Verify vent pipe is cool to the touch.
b. Disconnect power to furnace and remove vent con-
nector from furnace vent elbow.
c. Restore power to furnace and set room thermostat
above room temperature.
d. After normal start-- up, allow furnace to operate for 2
minutes, then block vent elbow in furnace 80 percent
of vent area with a piece of flat sheet metal.
e. Furnace should cycle off within 2 minutes. If gas does
not shut off within 2 minutes, determine reason draft
58CV
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