York YCAS0130 manual Thermal Overload, Current Imbalance Loaded & Unloaded/ Loss of Phase

Thermal Overload

Three PTC (positive temperature coefficient) thermistors in the motor windings provides thermal protection. The sensor resistance stays relatively constant at 1kΩ until a temperature of 266°F (130°C) is sensed. The sensor experiences a rapid rise in resistance beyond this tem- perature. Whenever the resistance of one of the sensors reaches 13kΩ, +/− 3kΩ, the 2ACE module trips, which ultimately de-energizes the motor’s pilot circuit. Reset is manual after the motor cools and the sensor resistance drops to 3.25kΩ, +/− 0.5kΩ.

Current Imbalance (Loaded & Unloaded)/ Loss of Phase

A 2 second delay at start-up allows for any imbalances resulting during normal starting conditions. After this initial delay, the 2ACE module compares the “Oper- ating Current” to the measured half line current. The “Operating Current” is given by 0.65 X factory overload current setting.

An unloaded compressor condition occurs when any measured half line current is less than the “Operating

FORM 201.19-NM1 (204)

Current.” A current imbalance exceeding an unloaded level of 25% will result in the motor pilot circuit being de-energized.

A loaded compressor condition occurs when any mea- sured half line current is greater than or equal to the “Operating Current.” A current imbalance exceeding a loaded level of 17% will result in the motor pilot circuit being de-energized.

Imbalance is defined as

(High Phase - Low Phase)/High Phase

Improper Phase Sequence

The 2ACE module calculates the phase sequence at start-up using the three current transformers to de- termine whether the three phase sequence on the load side of the main contactor is miswired. Upon detection of a miswired motor load, the module will de-energize the main contactor pilot circuit within 50 millisecond response time.

Additional information on the 2ACE MP module may be found on page 125.

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