Cornelius IAC227 Manual de usuario descargar pdf (Pagina 14)

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FAN CYCLING SWITCH (R404a Units)

The function of this switch is to maintain condensing pressures at a satisfactory level during–low ambient

conditions. The switch breaks the circuit to the condenser fan motor at 205 PSI and makes the circuit at 275

PSI.

HIGH PRESSURE CONTROL

The high pressure cut out is electrically in series with the contactor. As the head pressure rises to 450 PSIG,

for R404a charged units, a preset level the contact opens thus breaking the circuit to the compressor via the

contactor. This control must be reset manually on R404a units.

COMPRESSOR START RELAY

This is a current type relay and contains a N.O. contact which is connected in series with the start winding of the

compressor. The relay coil is electrically in series with the run winding. When power is applied, the compressor

draws high current which sets up a magnetic field around the magnet coil which causes the relay to operate,

closing the relay contact. As the compressor approaches operating speed, the current flowing through the coil

decreases, permitting the relay contact to open, thereby opening the starting circuit.

POTENTIAL RELAYS

The potential relay is used as a compressor starting relay, The contact in the potential relay is N.C.. The

magnet coil is connected across (parallel) the start winding and is affected by induced voltage, generated by the

start winding. As the compressor comes up to design speed, the voltage across the relay coil increases and at

running speed is sometimes as much as 2 1/2 times the supply voltage. This voltage sets up a magnetic field

which causes the relay to operate. The starting relay is calibrated to remove the start capacitor (open the

starting circuit) at approximately 80% of the compressor operating speed.

NOTE: BOTH TYPES OF RELAYS ARE DESIGNED TO OPERATE WITHIN VERY NARROW LIMITS OF

VOLTAGE AND CURRENT DICTATED BY MOTOR DESIGN, THEREFORE, WHEN MAKING A

REPLACEMENT OF A RELAY ALWAYS PROVIDE AN EXACT REPLACEMENT RECOMMENDED

BY THE COMPRESSOR MANUFACTURER.

CAPACITORS – GENERAL

An electrical capacitor is a device which stores up electrical energy. Capacitors are used with single phase

motors to provide starting torque and improve running characteristics; by feeding this energy to the start winding

in step with the run winding.

Any capacitor has three (3) essential parts, two (2) of which are usually foil plates separated and insulated by

the third part called the dielectric.

Two general types of capacitors are used with electric motors. The electrolytic starting capacitor usually uses a

very thin film of oxide on the metallic plate as the dielectric. The running capacitor usually is of the liquid filled

type. and remains in the circuit during both the start and run operation.

DUMP SWITCH

This switch activates the evaporator dump valve manually. This allows the draining of the evaporator for service

or cleaning. Dumping the water every 24 or 48 hours will reduce the down time for cleaning in high mineral

content water areas.

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Cornelius IAC227 Manual de usuario Pagina 14