RWF ROTARY SCREW COMPRESSOR UNITS
MAINTENANCE
S70-600 IOM (OCT04)
Page 32
SV POSITION POTENTIOMETER
REPLACEMENT AND ADJUST MENT
The Slide Valve Position potentiometer is located on the end
of the compressor unloader cylinder (applies to models 100
- 270), see Figure 26.
POTENTIOMETER
FLEXIBLE
COUPLING
COVER
LOCKNUT
Figure 26
1.
Shut off control power.
2.
Remove the four socket head cap screws securing the
potentiometer cover to the unloader cylinder.
3.
Unsolder leads to the potentiometer and remove.
4.
Loosen the setscrew on the potentiometer side of the
flexible coupling.
5.
Remove the three retainer clips securing the poten tiometer
to the base plate. The potentiometer should slip out of the
coupling.
6.
Install the new potentiometer and reassemble.
7.
Adjustment:
ROUGH ADJUSTMENT
is made with the slide valve fully
unloaded and the control power off. Remove connector P5.
With a digital voltmeter, measure the resistance across the
red and white wires, having removed them from the SBC.
The resistance should be 1000 +/- 50 ohms. If adjustment is
necessary, loosen the locknut and rotate the potentiometer
clockwise or counterclock wise until the resistance reading
is a close to a 1000 ohms as possible. Retighten the locknut
and replace wires.
NOTE: Mechanical travel of the slide
valve potentio meter is 300 degrees rotation when the
slide stop is confirmed to be in the 2.2 Vi position. The
travel will be less than 300 degrees if the slide stop is
in any position above 2.2 Vi.
FINE ADJUSTMENT
must be made with the slide valve fully
unloaded and the compressor running. The Operating display
at this time should indicate a slide valve position of 0%. If
the display is greater than 0%, adjust potentio meter POT
#4 on the SBC until 0% is indicated. If 0% is not attainable,
get as close as possible and then proceed to the next step.
The adjust ments of POT #4 and POT #3 are interactive and
POT #3 may require adjustment to allow POT #4 to come
into range.
Completely load the slide valve. The display at this time
should indicate 100%. If the display is less than 100%, adjust
potentiometer POT #3 on the SBC until 100% is indicated.
Repeat this sequence until the slide valve indicates 0% fully
unloaded and 100% fully loaded.
CAPACITY LINEAR TRANSMITTER
REPLACEMENT - SLIDE VALVE
The Capacity Linear Transmitter is located on the end of the
compressor unload cylinder (applies to models 100 - 270),
see Figure 27.
END VIEW
DIN CONNECTOR
STAINLESS STEEL WELL
HEAT ISOLATOR
CAST ALUMINUM HOUSING
COMPRESSOR UNLOAD CYLINDER
SHADED AREA SHOWS
CAPACITY LINEAR TRANSMITTER
Figure 27
The linear transmitter with hermetic enclosure is based on
the inductive measuring principle. It features removable elec-
tronics (from the sensor well) eliminating the need to evac-
uate the compressor for replacement. This type of transmitter
is dedicated to capacity control and is not adjustable.
1.
Shut off control power.
2.
Remove DIN connector plug from transmitter.
3.
Loosen cap screws.
4.
Remove transmitter unit.
5.
Install new transmitter unit.
6.
Tighten cap screws.
4.
Loosen screw and disconnect wiring harness connector
from transducer.
5.
Unscrew the transducer using a wrench on the metal hex at
the base of the transducer.
DO NOT ATTEMPT TO LOOSEN
OR TIGHTEN TRANSDUCERS BY THEIR TOP CASING.
6.
Install new transducer.
7.
Reconnect the wiring harness to the transducer.
8.
Reopen the transducer isolation valve.
9.
Turn on control power.
NOTE: The Pressure Transducer is factory set. If calibra-
tion is required, refer to Amalog Calibration Instruction
in publication S90-010 M-ADD.
