Compressor & Starting Component Check-Out Procedure; Relay; Potential; Current - Cornelius XAC 1444 Service Training Manual

Xtreme Ice Training Manual
COMPRESSOR & STARTING COMPONENT CHECK-OUT PROCEDURE
When a compressor fails to start or run properly, it is normally the external electrical supply or the com-
pressor start components that are defective – the overload protector, start and/or run capacitor, relay,
circuit board, safety controls, etc.
1. Check voltage at compressor terminals. NO voltage will require checking the electrical circuit work-
ing back from the compressor to determine where the voltage supply is interrupted and correct as
required. The load voltage, while compressor is trying to start, should not be less than 90% of rated
required voltage.
Line voltage and wire size effect the life expectancy of the electrical components, compressor, motor
winding, solenoid coils, etc.
Poor line quality voltage will cause many erratic electrical problems. Remember every electrical product,
ice machine, dispenser, walk-in, reach-in, air conditioner, etc. required proper power supply to operate.
Be certain when voltage checks are performed that you are measuring load voltage, not line voltage.
2. A defective capacitor or start relay may prevent the compressor from starting. Should the compres-
sor attempt to start, but is unable to do so, or if the compressor hums or trips off on the over protec-
tor, check the following:
NOTE: For 50 HZ application on dual rated 50/60 HZ models, load voltage while compressor is
starting must not be less than 90% of 50 HZ rating.

Relay

Potential –
For the potential type, contacts are normally closed. The start contacts open by C.E.M.F. generated by
the compressor at approximately 80% of the normal operating speed. The run winding and the run capac-
itor remain in the circuit. This relay may or may not be directional in mounting.
Current –
For the current type, contacts are normally open. The start contacts close by the high current draw from
the locked rotor condition with only the run winding in the circuit. As the contacts close, the start capacitor
and the start winding is energized and the compressor starts. At approximately 80% of its operating
speed the current draw drops off, the relay contacts open removing the start winding and start capacitor
from the circuit. (Remember, current relays are directional in their mounting to allow contacts to
lift and close).

Capacitors

A quick check is to replace suspected defective capacitors with known good capacitors being careful to
stay within the range for substitute values. Should those values be unknown, a basic rule for capacity is:
for start capacitors 10% and run capacitors 5% of the rating on the defective original capacitor being
replaced. Voltage should always try and be matched; if it cannot be, it is acceptable to increase up to
10% higher than the voltage listed on the capacitor being replaced. NEVER put a capacitor on a product
with a voltage rating lower than the original being replaced. If a capacitor analyzer is not available, an
ohm meter may be used to check a capacitor for short or open circuits. Set the ohm meter to its highest
scale and connect its leads to the capacitor terminals.
1. With a capacitor, without plate defect, the indicator should first move to zero (0) and then gradually
increase to infinity.
2. If there is no movement of the ohm meter indicator, an open circuit is indicated.
3. If the ohm meter indicator moves to zero (0) and remains there, or on a low resistance reading, a
short circuit is indicated.
4. Please note this check does not determine if the capacitor will deliver the proper rated MFD/UFD
required, it only shows if the capacitor has shorted or open circuits.
5. Capacitors that show any signs of leakage of electrolyte, or damage of the can, should be replaced.
DO NOT TEST!
October 17, 2005 33 TP00952