Service manual

32
Installation and Service Manual
COMPONENT DIAGNOSTICS
COMPRESSOR AND STARTING COMPONENTS CHECK OUT PROCEDURE
When compressors fail to start or run properly, it is
normally the external electrical supply or start components
that are defective. The over-load protector, start and/or run
capacitor, relay, control board, safety controls, etc:
1. With machine in ice position and contactor closed,
check voltage at compressor terminals. NO volt-
age will require a back check from compressor to
determine where the voltage supply is interrupted.
Correct as required. The load voltage, while com-
pressor is trying to start, should not be less than
95% of rating required for product.
Line voltage and line size effect life expectancy of
electrical components, compressor, motor coils,
etc. Line voltage should be maintained at 95% of
lowest rated voltage.
NOTE: For 50 HZ application on dual rated 50/60 mod-
els, load voltage, while compressor is starting
must not be less than 95% of 50 HZ rating.
NOTE: Poor line quality voltage will cause many er-
ratic electrical problems. Every electrical prod-
uct, ice machine, dispenser, walk-in, reach-in,
air conditioner, etc. requires proper power sup-
ply to operate. Be certain your voltage check is
load voltage, not line.
2. A defective capacitor or relay may prevent the
compressor from starting. If the compressor at-
tempts to start, but in unable to do so, or if the
compressor hums or trips out on the over-load
protector, check:
Relay - Potential type, contacts normally closed.
Contacts open by C.E.M.F. from compressor at
approximately 80% of operating speed remov-
ing start capacitor from circuit. Both start and run
winding and run capacitor remain in circuit.
Capacitors - Any capacitor found to be bulging,
leaking or damaged should be replaced.
CAUTION: Before removing leads for testing pur-
poses, short across capacitor with a 10K OHM re-
sistor to discharge capacitor if capacitor does not
have bleed resistor installed.
A quick check is to replace suspected capacitors with a
known good capacitor. Be sure specified capacities are used.
If capacitor analyzer is not available, an OHM meter
may be used to check start capacitors for short, or open,
circuits. Set the OHM meter to its highest scale and con-
nect prods to capacitor terminals.
A) With a good capacitor, the indicator should first move
to zero (0) and then gradually increase to infinity.
B) If ther is no movement of the OHM meter indica-
tor, an open circuit is indicated.
C) If the OHM meter indicator moves to zero (0)
and remains there, or on low resistance read-
ing, a short circuit is indicated.
D) Remember this check does not determine that
capacitor will deliver the MFD/UFD rating re-
quired, only detects shorted or open plates.
E) Capacitors that show any sign of leakage of elec-
trolyte, or damage of can, should be replaced.
DO NOT TEST!
CAUTION: Turn power off. Before removing supply
leads to compressor, short across both capacitor
terminals to discharge capacitors.
1. Using an OHM meter check for continuity from
terminals C to R, and C to S. If the compressor
is hot, wait one (1) hour for compressor to cool
and recheck. the internal over-load protector can
cause a lack of continuity. If continuity cannot
be established through all motor windings, the
compressor must be replaced.
2. Check compressor for ground by means of a
continuity check between terminals C, R and S
to the compressor shell or copper refrigeration
line (be sure to scrape metal surface clean to
get good contact). Continuity present, the com-
pressor windings are grounded and the com-
pressor must be replaced.
If compressor starts, but trips, repeatedly on the over-
load protector, check:
Operating pressures should be within limitations of
normal operating conditions.
Check the amperage drawn while the compressor is
operating. Under normal operating condintions, the con-
tinuous amperage drawn will seldom exceed 100% of
compressor nameplate amperage and should never ex-
ceed 120% of nameplate amperage. High amperage can
be caused by: Low Voltage, Undersized Lines, High
Head Pressure, High Suction Pressure, Defective
Running Capacitors or Starting Relay, Compressor
Mechanical Damage.