Ingersoll-Rand 7100 Pressure Switch Adjustment, Starting Unloading System, Auxiliary Valve, Psig

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Auxiliary Valve. Pressure Switch Range Adjustment.

Select constant speed control if the unit restarts in less than 10 minute intervals or runs more than 40 minutes per hour. Turn the knob fully counterclockwise to run the unit continually. When the receiver tank pressure reaches 170 PSIG, the unit runs but does not pump.

NOTE	The auxiliary valve is factory pre-set at 5 PSIG lower
	than the factory pressure switch setting.
•CAUTION	Running unloaded for more than 20 minutes per
	hour or more than 15 minutes continually with the
	use of constant speed control will cause oil
	pumping and should be avoided.

PRESSURE SWITCH ADJUSTMENT ____________________

•WARNING	High voltage is present at the pressure switch
	contacts when the power supply is connected.
	Disconnect, lock and tag main power supply before
	making adjustments.
•CAUTION	Do not adjust the pressure switch to exceed the
	maximum discharge pressure of the unit.
NOTE	Adjust the pressure switch only if adjustments are
	absolutely necessary.

CUT-IN & CUT-OUT.The cut-out (compressor shut-down) is the pressure at which the switch contacts open, and the cut-in (compressor restart) is the pressure at which the switch contacts close. See COMPRESSOR CONTROLS.

ADJUSTMENT CONTROLS. All pressure switches have a range adjustment control (A). Some pressure switches also have a differential adjustment (B) control. On switches without a differential adjustment control, the span between cut-in and cut-out pressure levels switches is factory set for 40 ± 4 PSIG and cannot be adjusted.

NOTE	Some pressure switches are equipped with an
	on-off lever used to open and close the electrical
	contacts inside the switch. THIS LEVER IS NOT A
	DIFFERENTIAL ADJUSTMENT CONTROL. The
	pressure switches with the on-off lever do not have
	a differential adjustment control.

ADJUSTMENT PROCEDURES (SWITCHES WITHOUT DIFFERENTIAL ADJUSTMENT CONTROL):

1.Remove the pressure switch cover.

2.Adjust the range by turning the range adjustment screw clockwise (in) to increase the cut-out point or counter-clockwise (out) to decrease the cut-out point.

NOTE:	One full turn changes the setting approximately 2
	PSIG.

3.Replace cover, reconnect power supply and start the compressor.

4.Note the pressure gauge reading at which the compressor cuts out.

5.Repeat adjustment procedure if necessary.

ADJUSTMENT PROCEDURES (SWITCHES WITH DIFFERENTIAL ADJUSTMENT CONTROL):

1.Remove the pressure switch cover.

2.Set the cut-in pressure with the range adjustment nut. Turn the nut

clockwise (in) to increase the pressure or counter-clockwise (out) to decrease the pressure.

NOTE: One full turn changes the setting approximately 2 PSIG.

3.Set the cut-out pressure with the differential adjustment. Turn the

differential adjustment nut clockwise (in) to increase the pressure or counter-clockwise (out) to decrease the pressure.

NOTE: One full turn changes the setting approximately 2 PSIG.

4.Replace the cover, reconnect the power supply and start the unit.

5.Note the pressure gauge reading at which the unit cuts out.

6.Repeat the adjustment procedure if necessary.

The minimum possible differential is approximately 20% of cutout pressure. It is advisable to have as wide a differential as possible to avoid frequent starting and stopping of the unit. Note the pressure gauge reading at which the unit cuts-out and re-establish this point if necessary.

Note the interaction between the range and differential adjustments, i.e., if the cut-out is increased, the differential will also increase, or if the differential is narrowed, the cut-out will be reduced, etc. These factors must be considered when adjusting the switch and compensated for accordingly.

STARTING UNLOADING SYSTEM ______________________

The starting unloading feature exists on certain models. The purpose of the system is to relieve cylinder pressure when the unit stops, permitting it to start against a light load. A light load increases the life of the driver and belts and also reduces the possibility of tripping the overload relay. The system operates in the following manner:

The centrifugal unloader is attached to the end of the crankshaft as shown in the following illustrations.

When the unit starts, centrifugal force acts upon the unloader weights and they swing outward. This permits the plunger and thrust pin to move inward and the pilot valve to close. The escape path to atmosphere for the cylinder pressure is now closed and the compressor pumps air in a normal manner.

When the unit stops, the weights retract, permitting the thrust pin spring to move the plunger and thrust pin outward. The thrust pin opens the pilot valve and the trapped air pressure escapes from the cylinder and intercooler through a passage in the frame end cover, through the unloader tube and to atmosphere through the inlet filter/silencer.

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