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Electrical Data 1
Electrical Information
Ingersoll-Rand Impact
™
Compressors comply with all applicable Underwriters Laboratories standards
and the National Electrical Code, specifically, Article 440, Air-Conditioning and Refrigerating
Equipment. The Scope of Article 440 includes: “
electric motor driven air-conditioning and
refrigeration equipment and to the branch circuits and controllers for that equipment. It provides for
the special considerations necessary for circuits supplying hermetic refrigerant motor compressors and
for any air-conditioning and refrigeration equipment that is supplied from a branch circuit that supplies
a hermetic refrigerant motor compressor
.”
Rated Load Current
“Rated-Load Current” (RLC) is defined in Article 440 of the National Electrical Code as; the rated-load
current for a hermetic refrigerant motor compressor is the current resulting when the motor compressor
is operated at the rated load, rated voltage and rated frequency of the equipment it serves.
The rated-load current, sometimes referred to as rated load amperes (RLA), is typically established by
calculating the value from testing a compressor and determining the Maximum Continuous Current
(MCC). This MCC value is established by testing at a set rating condition as determined by UL
Standard 984 – Hermetic Refrigerant Motor Compressors Section 30. The conditions are determined by
the following temperature ranges, from UL 984 - Section 30 - Table 30.1.
Test Temperature Conditions
Return Gas
Evaporator
Temperature
Rating (
°
F)
Saturated Vapor
Temperature (
°
F)
Superheat
(
°
F)
Saturated
Discharge
Temperature (
°
F)
Ambient
Temperature
(
°
F)
+32 to +53.5 53.5 26.5 154 115
-10 to +32 32 48 140 122
-40 to +10 10 70 131 110
Once the MCC is determined, the RLA can be calculated in one of several methods. These methods are
defined in the National Electrical Code Section 440 Clause 52. These methods are duplicated in the
standard, UL 1995
Heating and Cooling Equipment .
There are several methods available to protect the motor-compressor against overload and failure to
start. The method employed on Ingersoll-Rand compressors vary by application temperature range and
refrigerant used. The chart below lists the method used.