Mike Holt’s Illustrated Guide to
Understanding the NEC® Requirements for
Article 440
Air-Conditioning and
Refrigeration Equipment
Extracted from Mike Holt’s Illustrated Guide to
Understanding the National Electrical Code, Volume 1
2008 Edition
Mike Holt Enterprises, Inc.
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ARTICLE
440
Air-Conditioning
and Refrigeration
Equipment
IntroDUctIon to artIcLe 440—aIr-conDItIonIng anD reFrIgeratIon eQUIPMent
This article applies to electrically driven air-conditioning and refrigeration equipment. The rules in this article add to, or amend, the rules
in Article 430 and other articles.
Each equipment manufacturer has the motors for a given air-conditioning unit built to its own specifications. Cooling and other characteristics are different from those of nonhermetic motors. For each motor, the manufacturer has worked out all of the details and supplied the
correct protection, conductor sizing, and other information on the nameplate.
The application itself—with the compressor motor often on the other side of an exterior building wall from the normal power sources so
it can exchange heat with free air—poses additional problems, which the NEC addresses in Article 440.
Part I. generaL
440.1 scope. Article 440 applies to electrically driven airconditioning and refrigeration equipment.
440.2 Definitions.
Hermetic Refrigerant Motor-Compressor. A compressor
and motor enclosed in the same housing, operating in the
refrigerant.
rated-Load current. The current resulting when the
motor-compressor operates at rated load and rated voltage.
440.3 other articles.
(B) Equipment with No Hermetic Motor-Compressors. Airconditioning and refrigeration equipment that do not have
hermetic refrigerant motor-compressors, such as furnaces
with evaporator coils, must comply with Article 422 for
appliances, Article 424 for electric space-heating, and Article
430 for motors.
(C) Household Refrigerant Motor-Compressor Appliances.
Household refrigerators and freezers, drinking water coolers,
and beverage dispensing machines are listed as appliances,
and their installation must also comply with Article 422 for
appliances. Figure 440–1
Figure 440–1
440.6 ampacity and rating.
(A) Hermetic Refrigerant Motor-Compressor. For a hermetic
refrigerant motor-compressor, the rated-load current marked
on the nameplate of the equipment is to be used in determining the rating of the disconnecting means, the branch-circuit
conductors, the controller, and the branch-circuit short-circuit and ground-fault protection.
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440.6
Air-Conditioning and Refrigeration Equipment
Exception No. 1: The branch-circuit selection current must be
used instead of the rated-load current if provided on the equipment nameplate.
Part II. Disconnecting Means
Author’s Comment: “Within Sight” is visible and not more than
50 ft from each other [Article 100].
The disconnecting means can be mounted on or within the
air-conditioning equipment, but it must not be located on
panels designed to allow access to the equipment, or where it
will obscure the equipment name­plate. Figure 440–4
440.14 Location. The disconnecting means for air-conditioning or refrigeration equipment must be located within
sight from and readily accessible from the equipment. Figures
440–2 and 440–3
Figure 440–4
Figure 440–2
Exception No. 1: A disconnecting means isn’t required to be
within sight from the equipment, if the disconnecting means is
capable of being individually locked in the open position, and
if the equipment is essential to an industrial process in a facility that has written safety procedures, and where the conditions
of maintenance and supervision ensure only qualified persons
service the equipment. The provision for locking or adding a
lock to the disconnecting means must be on the switch or circuit breaker, and it must remain in place with or without the
lock installed.
Exception No. 2: An accessible attachment plug and receptacle
can serve as the disconnecting means.
Author’s Comment: The receptacle for the attachment plug
isn’t required to be readily accessible.
Figure 440–3
2
Mike Holt’s Illustrated Guide to Understanding the National Electrical Code, Volume 1
Air-Conditioning and Refrigeration Equipment
440.32
Part III. oVercUrrent ProtectIon
440.21 general. The branch-circuit conductors, control
apparatus, and circuits supplying hermetic refrigerant motorcompressors must be protected against short circuits and
ground faults in accordance with 440.22.
Author’s Comment: If the equipment nameplate specifies
“Maximum Fuse Size,” then a one-time or dual-element fuse
must be used.
440.22 short-circuit and ground-Fault overcurrent
Device size.
(A) Single Motor-Compressors. The short-circuit and groundfault protective device must not be more than 175 percent of
the motor-compressor current rating. If the protective device
sized at 175 percent isn’t capable of carrying the starting current of the motor-compressor, the next size larger protective
device can be used, but in no case can it exceed 225 percent
of the motor-compressor current rating.
Question: What size conductor and protection are required for
a 24A motor-compressor connected to a 240V circuit? Figure
440–5
(a) 10 AWG, 40A
(c) a or b
(b) 10 AWG, 60A
(d) 10 AWG, 90A
Answer: (a) 10 AWG, 40A
Figure 440–5
(1) Motor-Compressor Largest Load. The rating of the
branch-circuit short-circuit and ground-fault protective
device must not be more than the largest motor-compressor
short-circuit ground-fault overcurrent device, plus the sum
of the rated-load currents of the other compressors.
Author’s Comment: The branch-circuit conductors are sized
at 125 percent of the larger motor-compressor current, plus
the sum of the rated-load currents of the other compressors
[440.33].
Step 1: Determine the branch-circuit conductor [Table 310.16
and 440.32]:
24A x 1.25 = 30A, 10 AWG, rated 30A at 75°C
[Table 310.16]
Step 2: Determine the branch-circuit protection [240.6(A) and
440.22(A)]:
24A x 1.75 = 42A, next size down = 40A
If the 40A short-circuit and ground-fault protective
device isn’t capable of carrying the starting current, then the protective device can be sized up to
225 percent of the equipment load current rating.
24A x 2.25 = 54A, next size down 50A
(B) Several Motor-Compressors. Where the equipment incorporates more than one hermetic refrigerant motor-compressor, or a hermetic refrigerant motor-compressor and other
motors or other loads, the equipment short-circuit and
ground-fault protection must be sized as follows:
Part IV. conDUctor sIZIng
440.32 conductor size for single Motor-compressors. Branch-circuit conductors to a single motor-compressor must have an ampacity not less than 125 percent of the
motor-compressor rated-load current or the branch-circuit
selection current, whichever is greater.
Author’s Comment: Branch-circuit conductors for a single
motor-compressor must have short-circuit and ground-fault
protection sized between 175 percent and 225 percent of the
rated-load current [440.22(A)].
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440.32
Air-Conditioning and Refrigeration Equipment
Question: What size conductor and overcurrent device are
required for an 18A motor compressor? Figure 440–6
(a) 12 AWG, 30A
(c) a or b
(b) 10 AWG, 50A
(d) 10 AWG, 60A
Answer: (a) 12 AWG, 30A
Step 1: Determine the branch-circuit conductor [Table 310.16
and 440.32]:
18A x 1.25 = 22.50A, 12 AWG, rated 25A at 75°C
[Table 310.16]
Step 2: Determine the branch-circuit protection [240.6(A) and
440.22(A)]:
18A x 1.75 = 31.50A, next size down = 30A
If the 30A short-circuit and ground-fault protection
device isn’t capable of carrying the starting current, then the protective device can be sized up to
225 percent of the equipment load current rating.
18A x 2.25 = 40.50A, next size down 40A
440.33 conductor size for several Motor-compressors. Conductors that supply several motor-compressors
must have an ampacity not less than 125 percent of the highest motor-compressor current of the group, plus the sum of
the rated load or branch-circuit selection current ratings of
the other compressors.
Author’s Comment: These conductors must be protected
against short circuits and ground faults in accordance with
440.22(B)(1).
Part VII. rooM aIr conDItIoners
The requirements in this Part apply to a cord-and-plug-connected room air conditioner of the window or in-wall type
that incorporates a hermetic refrigerant motor-compressor
rated not over 40A, 250V, single-phase [440.60].
440.62 Branch-circuit requirements.
(A) Sizing Conductors and Protection. Branch-circuit conductors for a cord-and-plug-connected room air conditioner
must have an ampacity not less than 125 percent of the ratedload currents [440.32].
(B) Separate Circuit. Where the room air conditioner is the
only load on a circuit, the marked rating of the air conditioner must not exceed 80 percent of the rating of the circuit
overcurrent device [210.3].
(C) Other Loads on Circuit. The total rating of a cord-andplug-connected room air conditioner must not exceed 50 percent of the rating of a branch circuit where lighting outlets,
other appliances, or general-use receptacles are also supplied.
Figure 440–7
440.63 Disconnecting Means. An attachment plug and
receptacle can serve as the disconnecting means for a room
air conditioner, provided: Figure 440–8
(1) The manual controls on the room air conditioner are
readily accessible and within 6 ft of the floor, or
Figure 440–6
Author’s Comment: A 30A or 40A overcurrent device is permitted to protect a 12 AWG conductor for an air-conditioning circuit.
See 240.4(G) for details.
4
(2) A readily accessible disconnecting means is within sight
from the room air conditioner.
Author’s Comment: “Within Sight” is visible and not more than
50 ft from each other [Article 100].
Mike Holt’s Illustrated Guide to Understanding the National Electrical Code, Volume 1
Air-Conditioning and Refrigeration Equipment
440.65
440.64 Supply Cords. Where a flexible cord is used to
supply a room air conditioner, the cord must not exceed 10 ft
for 120V units, or 6 ft for 208V or 240V units.
440.65 Leakage Current Detector-Interrupter and
Arc-Fault Circuit Interrupter. Single-phase cord-andplug-connected room air conditioners must be provided with
a factory-installed leakage current detector, or with an arcfault circuit-interrupter (AFCI).
Figure 440–7
Figure 440–8
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ARTICLE
Article 440
Practice Questions
440
Practice Questions
artIcLe 440. aIr-conDItIonIng
anD reFrIgeratIng eQUIPMent—
PractIce QUestIons
1.
4.
Article 440 applies to electric motor-driven air-conditioning and refrigerating equipment that has a hermetic
refrigerant motor-compressor.
(a) 100
(b) 125
(c) 150
(d) 200
(a) True
(b) False
2.
Equipment such as _____ shall be considered appliances,
and the provisions of Article 422 apply in addition to
Article 440.
(a) room air conditioners
(b) household refrigerators and freezers
(c) drinking water coolers and beverage dispensers
(d) all of these
Where the air conditioner disconnecting means is not
within sight from the equipment, the provision for
locking or adding a lock to the disconnecting means
shall be on the switch or circuit breaker and remain in
place _____ the lock installed.
5.
An attachment plug and receptacle can serve as the
disconnecting means for a single-phase room air conditioner rated 250 volts or less if _____.
(a) the manual controls on the room air conditioner are
readily accessible and located within 6 ft of the floor
(b) an approved manually operable disconnecting means
is installed in a readily accessible location within
sight from the room air conditioner
(c) a or b
(d) a and b
(a) with
(b) without
(c) with or without
(d) none of these
Answers:
1. (a) 440.1
2. (d) 440.3(C)
3. (c) 440.14 Ex 1
4. (b) 440.32
5. (c) 440.63
3.
Branch-circuit conductors supplying a single a/c motorcompressor shall have an ampacity not less than _____
percent of either the motor-compressor rated-load
current or the branch-circuit selection current, whichever
is greater.
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Mike Holt’s Illustrated Guide to Understanding the National Electrical Code, Volume 1