29
Set the meter for DC amps and record value in Amps DC.
If measured value is greater than, or equal to, .25 Amps, a problem exists.
Isolate electrical devices in compressor package and determine the source of
ground current.
Causes may include: faulty wiring, moisture contamination of electrical
connections, motor overloads (current transformer type), control transformer,
insulation breakdown of power leads, externally wired devices (remote start/stop,
remote starter wiring, Sequencer, IRI, etc.)
1.4 Intellisys 16 VAC supply:
Background
The Intellisys power supply is fed from the 16 VAC center-tap secondary of the
control power transformer T1. The center-tap indicates a central tap between the
16 VAC winding. This means the expected voltage across one end of the
winding and the center-tap will be 8 VAC. The expected reading of the 16 VAC
signal should have a tolerance of +/-15 %. The 16 VAC center-tap signal is fed
to the Intellisys through the J4 connector. The signal is rectified by diodes CR1
and CR2. The resulting rectified DC signal is approximately 10.5 VDC. The
Intellisys is designed to accommodate +/- 25 % tolerance. Deviations in excess
of +/-25%, or a loss of this signal, can cause the machine to shut down and reset
to “Ready to Start”.
Procedure
This voltage measurement can be made with a Fluke 87 meter (or equivalent). A
recording meter (Fluke 87) is preferred for intermittent problems. Set meter for
Volts AC and connect as noted.
Connect from J4-30 to J4-31.
Expected value =16 VAC +/- 2.4 VAC
Connect from J4-29 to J4-30.
Expected value = 8 VAC +/- 1.2 VAC
Connect from J4-29 to J4-31.
Expected value = 8 VAC +/- 1.2 VAC
Connect from J4-28 to J4-29.
Expected value = 10.5 VDC +/- 1.6 VDC
If the expected values are not observed, possible causes may include:
Primary voltage is in excess of 15% tolerance.
Wiring fault: Check primary and secondary wiring for errors, loose connection or
crimp, frayed ends, insulation breakdown, moisture contamination.
Fuse problem: blown fuse (primary or secondary), loose connection, voltage drop
across fuse: >.5 VAC excessive control system current: Remove power and
disconnect all but J5 connector to Intellisys (also remove option prom and
communications wiring). Apply power and record measurements. If
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