Equipment & SystemsQuestion 257 of 521
On an air-conditioning unit nameplate, what does the 'Minimum Circuit Ampacity (MCA)' value tell the installer?
a.The minimum ampacity the branch-circuit conductors must have
b.The maximum fuse or breaker size allowed
c.The full-load current of the condenser fan only
d.The locked-rotor current of the compressor
Explanation
MCA is the minimum conductor ampacity required to supply the unit, already calculated by the manufacturer (125% of the largest motor plus other loads). The maximum overcurrent device is the separate MOCP/'Max Fuse' value; MCA is not a fan rating or locked-rotor value.
Law Reference: 2023 NEC §440.4Practice all 521 questions free — no signup required.
Related questions on this topic
- In a motor installation, what is the primary function of the motor controller?
- A motor control circuit tapped from the load side of the motor branch-circuit protection is generally protected against overcurrent according to which NEC provision?
- A single hermetic refrigerant motor-compressor has a rated-load current of 24 A. Per NEC 440.32, what minimum branch-circuit conductor ampacity is required?
- The 'Maximum Overcurrent Protective Device' (MOCP or 'Max Fuse/HACR Breaker') rating on an HVAC nameplate specifies what?
- An A/C condensing unit has a compressor rated-load current of 18 A and a fan motor of 2 A. Using the 125%-of-largest-motor-plus-others method, what is the minimum circuit ampacity (MCA)?
- For a hermetic motor-compressor with a rated-load current of 18 A, what is the maximum branch-circuit short-circuit/ground-fault protective device, based on the 175% value of NEC 440.22(A)?
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