Adjustments - Johnson Controls Penn P28 Series Manual

Crankcase
Runlight
Heater
if Used
When Used*
240
3
L
1
2 *
M
Alarm
if Used
A
120
P28 or P128
*When crankcase heater is used, disconnect jumper from 2 to M
and reconnect 2 to L.
Figure 8: P28 or P128 Where Manual "Start-Stop"
Pushbutton Station is Used (Jumper between
2 and M [or L] must be field installed.)
Alarm
if Used
Operating
3
Control
L
1
2
M
A
24*
P28 or P128
*12 volt also available.
Figure 9: P28 or P128 Where 24V Control Circuit
Power is from a Step-down Transformer (Jumper
between 2 and M must be field installed.)
6 P—P28 and P128 Series Lube Oil Controls with Built-in Time Delay Relay Product/Technical Bulletin
240V
3-phase
L L
1 2
Start
C
2
C
3
Stop
T T
1 2
Motor
Additional controls
in this line only.
240V
Transformer
3-phase
L L L
1 2 3
Starter Coil
T T T
1 2 3
Motor
Additional controls
in this line only.
Compressor
L
Motor
3
P74AA
Low
Oil
T
3
Note: This system would provide shutdown on low
lube oil pressure in either of two compressors
operated by the common motor.
Figure 10: P28 or P128 and P74AA Wired for an
Oil Pressure Control System Where One Motor
Operates Two Compressors

Adjustments

The P28 and P128 controls are shipped with a cut-out
pressure differential of 9 psi (62 kPa). However, the
controls can be adjusted according to the compressor
manufacturer's specifications.
Note: When the controls are shipped as an
accessory to the compressor unit, time delay
and cut-out pressure are set to manufacturer's
specifications. Replacement controls should
duplicate the manufacturer's specifications.
!
CAUTION: Equipment damage hazard.
When the manufacturer's specifications are not
known, proceed as follows to set the cut-out pressure
differential:
1. With the compressor running, read the oil
pressure and the crankcase pressure.
2. Subtract the crankcase pressure reading from the
oil pressure pump discharge reading. This is the
net oil pressure to the bearings.
3. Set the cut-out pointer 6 to 8 psi (41 to 55 kPa)
below the established running net oil pressure with
the Adjusting Disk using a standard screwdriver.
Operating
240 V
Control
L
1
P28/P128
Low
1 240
L
2
M T
1
Oil
Junction Box
To avoid damage to the
compressor, obtain the
compressor manufacturer's net
oil bearing pressure
specifications as soon as
possible. If necessary, reset the
cut-out pressure difference to the
manufacturer's specifications.
L
L
2
3
T
T
2
3