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"Oil-Less” Scroll Medical Air Medical Systems

6.0 Inspection/Replacement Procedures

6.3 Readjustment of Cut-out and Cut-in Pressure

The cut-out pressure refers to the discharge air pressure at which the unit will stop and is indicated by the
gauge near the electrical cabinet.

!!WARNING!!
IT IS STRICTLY PROHIBITED TO READJUST DISCHARGE AIR PRESSURE TO
MORE THAN THE SPECIFIED MAXIMUM PRESSURE (120 PSIG); NEGLECTING
IT MAY CAUSE HIGH DISCHARGE TEMPERATURE SHUTDOWN, MAIN
MOTOR OVERLOAD SHUTDOWN, OR SERIOUS COMPRESSOR BREAKDOWN.

The cut-in pressure refers to the discharge air pressure at which the compressor will start and is dictated by the
pressure and differential setting of the pressure switch. The standard factory pressure switch settings for the
lead pressure switch (PS-1) is 110 psig for cut-out (open) pressure and 90 psig for cut-in (close) pressure.

CAUTION
Generally, a narrower differential requires a larger volume of receiver, and vice versa. The recommended
receiver volume in the instruction manual is based on the standard factory setting of 20 psig differential.
If a narrower differential is desired, install a larger volume receiver; otherwise the cycle of start/stop may
be shorter which could generate an undesirable effect on the unit.

Adjusting Instructions

FIRST - Adjust the range (screw “A”) to the required
cut-out pressure setting. Turning the screw clockwise
raises the cut-in and cut-out pressure settings equally.
SECOND - Adjust the differential (screw “B”) to the
required cut-in pressure setting. Turning the screw
clockwise will raise the cut-in pressure setting only.
Differential is the difference between cut-in and cut-out
settings.

Table 6-2 Factory Pressure Switch Settings

Pressure Switch Close Open
Fig. 6-5 Pressure Switch Lead (PS-1) 90 psig 110 psig
Lag 1 (PS-2) 85 psig 105 psig
80 psig
100 psig
Lag 2 (PS-3) - Tpx and Qpx Only
Lag 3 (PS-4) - Qpx Only 75 psig 95 psig

6-5