Chapter 9
Electrical and Mechanical
9.1 Introduction
This section of the manual contains drawings and schematics of the electrical and
mechanical piping systems.
9.2 Electrical Abbreviations and Terminology
a. RLA – Rated Load Amperage
1. Rated load amps is a measure of the current drawn by a compressor
when operated at compressor manufacturer rating conditions at
nominal voltage. This value is listed at U.L. and C.S.A. as “RLA”. It
is in agreement with the N.E.C. definition that the RLA be the current
draw when the compressor is delivering rated output.
b. LRA – Locked Rotor Amperage
1. The locked rotor amps of a compressor is the current value recorded
three seconds after rated voltage is applied under locked rotor
conditions from a 75 degree Fahrenheit motor soakout temperature
(The voltage drop is to be predetermined and adjusted accordingly
prior to testing). This value appears on the compressor serial plate and
on all compressor statistics sheets.
2. It may be well to note that the practice in the past was to show an
additional column marked, “LRA U.L. Test Report”. This is no longer
needed since the U.L. investigation work, regarding component rating,
will be guided by the compressor manufacturer’s published value.
c. MCC – Maximum Continuous Current
1. Maximum continuous current is a limiting ampere value that must not
be greater than 156% of the RLA of the compressor as marked on the
nameplate of the particular unit into which that compressor is applied.
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