ICP N9MP1 Service Manual page 8

Service Manual
Figure 5
Gas Pressure Testing Devices
Pressure Connections
3
2
1
0
1
2
3
Typical "U" Tube
Manometer
MANIFOLD PRESSURE AND ORIFICE SIZE FOR HIGH ALTITUDE APPLICATIONS
Table 2 NATURAL GAS
Heat Value Heat Value
0- - 1999
Btu/Cu.Ft.
(² ² ² ² × × × × wc)
800 3.5
850 3.5
900 3.5
950 3.5
1000 3.5
1050 3.2
1100 2.9
Orifice Size #42
"CLOCKING" GAS METER
1. Check with gas supplier to obtain ACTUAL BTU con-
tent of gas.
2. Turn "OFF" gas supply to ALL other gas appliances.
3. Time how many seconds it takes the smallest (normal-
ly 1 cfh) dial on the gas meter to make one complete
revolution.
440 08 2001 02
INCHES OF WATER
5 10
0
MAGNEHELIC
MAX. PRESSURE 15 PSIG
2000- - 2999 3000- - 3999
(² ² ² ² × × × × wc) (² ² ² ² × × × × wc)
3.5 3.5
3.5 3.5
3.5 3.5
3.5 3.5
3.4 3.3
3.1 3.0
2.8 2.7
#42 #42
(NATURAL GAS)
CHECKING MANIFOLD PRESSURE
1. Connect a manometer or Magnehelic gauge (0--12²
W.C. range) to the pressure tap on the "OUTLET" side
of the gas valve.
2. Turn gas "ON", fire the furnace, and remove adjust-
ment cover (screw--cap).
3. Turn adjustment screw clockwise (IN) to INCREASE
pressure, and counterclockwise (OUT) to DECREASE
pressure.
15
4. At altitudes BELOW 2,000¢ ¢ ¢ ¢ set manifold pressure to
3.5² W.C. for Natural Gas, and 10² W.C. for L.P. Gas.
5. For Natural Gas units ABOVE 2,000¢ ¢ ¢ ¢ , set manifold
pressure according to TABLE 2.
6. For L.P. Gas units ABOVE 2,000¢ ¢ ¢ ¢ , insure that orifice
size has been changed (per "National Fuel Gas Code"
-- Appendix "F") if gas supply has not already been de--
rated for altitude by the gas supplier.
7. For ALL UNITS ABOVE 8,000¢, contact the factory for
SPECIFIC de--rating information.
Elevation Above Sea Level
4000- - 4999 5000- - 5999
(² ² ² ² × × × × wc)
3.5
3.5
3.5
3.5
3.2
2.9
2.6
#42
4. Calculate input rate by using ACTUAL BTU content of
gas in formula shown in example.
Natural Gas
BTU Content
1,000
6
Single Stage Multi Position Furnace
6000- - 6999
(² ² ² ² × × × × wc) (² ² ² ² × × × × wc)
3.5 3.5
3.5 3.5
3.5 3.5
3.3 3.2
3.0 2.9
2.7 2.6
2.5 2.4
#42 #42
Example
No. of Seconds Time Per Cubic
Per Hour Foot in Seconds
3,600 48
1,000 x 3,600 ¸ 48 = 75,000 BTUH
7000- - 7999
(² ² ² ² × × × × wc)
3.5
3.5
3.4
3.1
2.8
2.5
2.3
#42
BTU Per
Hour
75,000