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Master Catalog 125
Pressure Controls Section P
Product/Technical Bulletin P28
Issue Date 0498
© 1998 Johnson Controls, Inc.
1
Part No. 24-7664-605, Rev. A
Code No. LIT-125420
The P28 and P128 Series Lube Oil Controls provide
dependable and economical oil pressure cut-out for
pressure-lubricated refrigeration compressors. The
field-adjustable pressure differential of these controls
provides compressor operation according to the
manufacturer’s specifications. The P28 and P128
controls operate by measuring the net lube oil pressure
and de-energizing the compressor if the pressure falls
below the differential setpoint.
Manual or automatic reset models are available with
factory set and sealed time delays of 30, 45, 60, 90,
or 120 seconds (all time delays may not be available
on all models). The P128 is the same control as the
P28 but with 1/4 inch male flare pressure connections.
Figure 1: P128AA
Features and Benefits
Built-in Time Delay Relay
with Ambient Compensation
Minimizes timing fluctuations due to temperature
variations
Trip-free Manual Reset Provides manual reset that cannot be overridden
by pressing and holding the reset button
Replaceable Time Delay
Relay Assembly
Allows easy field replacement of the time delay
relay and terminal board
Available with Runlight and
Alarm Terminals
Allows the control to be wired for normal oil
pressure runlight signals and shutdown alarm
circuits for remote monitoring of oil pressure
status
P28 and P128 Series Lube Oil Controls
with Built-in Time Delay Relay