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.
1.With disconnect switch open, remove field connected thermostat wire from terminal R, W1 and W2 on TB1. Place jumper wire between R, W1 and W2 to engage high stage heat. (note on 045 kbtu/hr units W2 is not used, only jumper R to W1).
2.See Figure in input rating section for gas valve adjustment.
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 high stage manifold pressure must be between 3.2 and 3.8 inches water column (3.5 nominal). Low stage manifold pressure must be between 1.7 to 2.3 inches water column (2.0 nominal).
3.To set low fire rate on 090, 115 and 140 kbtu/hr: Open disconnect switch, and remove jumper from R to W2. To set low fire manifold pressure, repeat steps above. Refer to Figure in input rating section for location of high and low stage adjustment.
For propane gas, the manifold pressure must be between
9.7and 10.3 inches water column (10.0 nominal). Low stage manifold must be between 5.7 and 6.3 inches water column (6.0 nominal).
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.
NOx Screen Check
Verify that the alignment of the NOx screens is at 6 o' clock. In jurisdictions that do not require low NOx emissions, NOx screens may be removed.
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 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 Y of terminal block TB1. The cooling is energized when the room temperature is above the thermostat set- point for cooling. The thermostat makes R to Y.
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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