39
441 01 2121 01
Table 14 − Orifice Size and Manifold Pressure (In. W.C.) 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
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
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
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
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
ALTITUDE
RANGE
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
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 ener-
gizes air−circulating blower motor, if furnace overheats.
By using this method to check limit control, it can be
established that limit is functioning properly and will op-
erate 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 con-
trol 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 per-
cent 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 reas-
on draft safeguard switch did not function properly
and correct condition.
f. Remove blockage from furnace vent elbow.
g. Switch will auto−reset when it cools.
To Next Page
Loading...
