With Power And Gas On:
2.Put unit into heating cycle and turn on all other gas consuming appliances.
INLET GAS PRESSURE
NATURAL Min. 5.0" W.C., Max. 10.0" W.C.
PROPANE Min. 11.0" W.C., Max. 14.0" W.C.
NOTE: Inlet Gas Pressure Must Not Exceed the Maximum Value Shown.
If operating pressures differ from above, make necessary pressure regulator adjustments, check piping size, etc., and/ or consult with local utility.
Manifold Pressure Check
The gas valve has a tapped opening to facilitate measure- ment of the manifold pressure. A “U” Tube manometer hav- ing a scale range from 0 to 12 inches of water should be used for this measurement. The manifold pressure must be measured with the burners operating.
To adjust the pressure regulator, remove the adjustment screw or cover on the gas valve. Turn out (counterclockwise) to decrease pressure, turn in (clockwise) to increase pressure. Only small variations in gas flow should be made by means of the pressure regulator adjustment. In no case should the final manifold pressure vary more than plus or minus 0.3 inches water column from the specified nominal pressure. Any major changes in flow should be made by changing the size of the burner orifices. The measured input rate to the furnace must not exceed the rating specified on the unit rat- ing plate.
For natural gas, the manifold pressure must be between 3.2 and 3.8 inches w.c. (3.5 nominal) for high fire and between 1.7 and 2.3 inches w.c. (2.0 nominal) for low fire.
For propane gas, the manifold pressure must be between
9.7and 10.3 inches w.c. (10.0 nominal) for high fire and be- tween 6.7 and 7.3 inches w.c. (7.0 nominal) for low fire.
Gas Input (Natural Gas Only) Check
To measure the gas input use a gas meter and proceed as follows:
1.Turn off gas supply to all other appliances except the unit.
2.With the unit operating, time the smallest dial on the meter for one complete revolution. If this is a 2 cubic foot dial, divide the seconds by 2; if it is a 1 cubic foot dial, use the seconds as is. This gives the seconds per cubic foot of gas being delivered to the unit.
3.INPUT=GAS HTG VALUE x 3600 / SEC. PER CUBIC FOOT
Example: Natural gas with a heating value of 1000 BTU per cubic foot and 34 seconds per cubic foot as determined by Step 2, then:
Input = 1000 x 3600 / 34 = 106,000 BTU per Hour. NOTE: BTU content of the gas should be obtained from the gas supplier. This measured input must not be greater than shown on the unit rating plate.
4.Relight all other appliances turned off in step 1. Be sure all pilot burners are operating.
Main Burner Flame Check
Flames should be stable, soft and blue (dust may cause or- ange tips but they must not be yellow) and extending directly outward from the burner without curling, floating or lifting off.
Temperature Rise Check
Check the temperature rise through the unit by placing ther- mometers in supply and return air registers as close to the unit as possible. Thermometers must not be able to sample temperature directly from the unit heat exchangers, or false readings could be obtained.
1.All registers must be open; all duct dampers must be in their final (fully or partially open) position and the unit operated for 15 minutes on HIGH FIRE before taking readings.
2.The temperature rise must be within the range specified on the rating plate.
NOTE: Air temperature rise is the temperature difference between supply and return air.
With a properly designed system, the proper amount of tem- perature rise will normally be obtained when the unit is oper- ated at rated input with the recommended blower speed.
If the correct amount of temperature rise is not obtained, it may be necessary to change the blower speed. A higher blower speed will lower the temperature rise. A slower blower speed will increase the temperature rise.
NOTE: Blower speed MUST be set to give the correct air temperature rise through the unit as marked on the rating plate.
REFRIGERATION SEQUENCE CHECK
With the disconnect switch open, remove the field connected thermostat wire from terminal R on TB1 terminal block. Place a jumper across terminals R and G, and across R and Y on TB1 terminal block. Close the disconnect switch. The follow- ing operational sequence should be observed.
1.Current through primary winding of transformer TRANS1 energizes the
2.To simulate a mechanical call for cooling from the wall thermostat, place a jumper across terminals R and Y1 of terminal block TB1.
3.UNIT WITH ECONOMIZER OPTION: The compressor circuit is interlocked through terminals 3 and 4 of the economizer module. If the outdoor air enthalpy (temperature and humidity) is not suitable for cooling, the economizer terminals will be closed permitting compressor to be energized.
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