Section 6
MAINTENANCE
21
Table 6-2 Modulating Control Pressure Settings
PRESSURE SWITCH MODULATING CONTROL VALVE
SETTING 250017--280
250025-299
Rising Pressure
(PSIG/BAR)
Falling Pressure
(PSIG/BAR)
Press. Switch Press. Switch Start Fully Start Fully
Opening PSIG/BAR Closing PSIG/BAR Unloading Unloaded Unloading Unloaded
100/6.9 70/4.8 87/6 95/6.6 93/6.4 85/5.9
125/8.6 95/6.6 112/7.7 120/8.3 118/8.1 110/7.6
150/10.3 120/8.3 137/9.4 145/10 143/9.9 135/9.3
175/12.1 145/10 162/11.2 170/11.7 168/11.6 160/11
switch and pressure regulator valve. This is done by
following the instructions below.
DANGER
!
DO NOT touch the electrical contacts, terminal or
leads with any part of the body or any uninsulated
metallic object. Severe electrical shock may oc-
cur.
PRESSURE SWITCH ADJUSTMENT
1.Close ball valve to isolate the pressure regulator
valve and set selector switch to manual.
2. Remomve the pressure switch cover.
3. With the shut--off valve closed or slightly cracked
open, start the compressor.
4. Observe the line pressure gauge and pressure
swithc contacts. When the line pressure reaches
nameplate pressure, the pressure switch con-
tacts should open.
5. If the pressure switch contacts do not open or
they open prior to the desired pressure, the pres-
sure switch setting will require adjustment (refer
to F igur e 6 -- 6) . To adjus t t he pr es s ur e s w itc h,
turn the range adjusting screw to the high--pres-
sure setting equally.
6. Replace pressure switch cover.
PRESSURE REGULATOR ADJUSTMENT
1. Establish correct pressure switch adjustment by
following the above procedure.
2. Lower line pressure by opening the shut--off valve
until the compressor reloads.
3. Loosen the pressure regulator locknut and open
ball valve.
4. Close shut--off valve; the pressure will increase
depending on the setting of the regulator adjust-
ment screw. Thighten adjustment screw until the
linepressuregauge reads a pressure of 5 psi/ .34
bar below the pressure switch setting estab-
lis hed in Table 6 -- 2.
5. Open shut--off valve and observe operation.
FOR DIFFERENTIAL ADJUSTMENT OF AIR
PRESSURE SWITCH:
Differential is the difference between the high and
low pressure settings.
Turning the screw clockwise increases the differen-
tial, and counterclockwise decreases the differential
pressure.
DANGER
!
DO NOT touch the electrical contacts, terminal or
leads with any part of the body or any uninsulated
metallic object. Severe electrical shock may oc-
cur.
UNLOADER SOLENOID VALVE MAINTENANCE
Unloader valve maintenance is minimal, but a peri-
odic cleaning is desirable. The time between clean-
ings will vary depending on operating conditions. In
general, if the voltage to the coils is correct, sluggish
valve operation or excessive leakage will indicate
that cleaning is required.
WARNING
!
Turn off all power,relieve sump pressure, and dis-
connect coil lead wires to the solenoid valve be-
fore making repairs.
It is not necessary to remove the valve from the pipe
line for repairs.
DISASSEMBLY AND REASSEMBLY
1. Remove the retaining cap and slip the entire sole-
noid off the solenoid base subassembly.
2. Unscrew the solenoid base assembly. Remove
the core assembly, core spring and body gasket.
3. All parts are now accessible for cleaning or re-
placement.
4. Reassemble in reverse order of disassembly.
COIL REPLACEMENT
1. Remove the retaining cap, nameplate and cover.
2. Slip the yoke containing the coil and sleeves off
the solenoid base subassembly.
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