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Extracted from Mike Holt’s Illustrated Guide to Understanding the National Electrical Code, Volume 1

2008 Edition

Mike Holt’s Illustrated Guide toUnderstanding the NEC® Requirements for

Article 440Air-Conditioning and

Refrigeration Equipment

Mike Holt Enterprises, Inc. • www.MikeHolt.com • 1.888.NEC.CODE (1.888.632.2633) 1

AR

TIC

LE 440Air-Conditioning and Refrigeration Equipment

440.6 ampacity and rating.

(A) Hermetic Refrigerant Motor-Compressor. For a her metic refrigerant motor-compressor, the rated-load current marked on the nameplate of the equipment is to be used in determin-ing the rating of the disconnecting means, the branch-circuit conductors, the controller, and the branch-circuit short-cir-cuit and ground-fault protection.

Part I. generaL

440.1 scope. Article 440 applies to electrically driven air-conditioning and refrigeration equipment.

440.2 Defi nitions.

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. Air-conditioning 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

IntroDUctIon to artIcLe 440—aIr-conDItIonIng anD reFrIgeratIon eQUIPMentThis 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 specifi cations. Cooling and other character-istics 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.

Figure 440–1

2 Mike Holt’s Illustrated Guide to Understanding the National Electrical Code, Volume 1

440.6 Air-Conditioning and Refrigeration Equipment

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 name plate. Figure 440–4

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 facil-ity 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 cir-cuit 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.

Exception No. 1: The branch-circuit selection current must be used instead of the rated-load current if provided on the equip-ment nameplate.

Part II. DIsconnectIng Means

440.14 Location. The disconnecting means for air-con-ditioning or refrigeration equipment must be located within sight from and readily accessible from the equipment. Figures 440–2 and 440–3

Figure 440–3

Figure 440–2

Figure 440–4


Air-Conditioning and Refrigeration Equipment 440.32

(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].

Part IV. conDUctor sIZIng

440.32 conductor size for single Motor-compres-sors. Branch-circuit conductors to a single motor-compres-sor 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)].

Part III. oVercUrrent ProtectIon440.21 general. The branch-circuit conductors, control apparatus, and circuits supplying hermetic refrigerant motor-compressors 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 ground-fault 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 cur-rent 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 (b) 10 AWG, 60A(c) a or b (d) 10 AWG, 90A

Answer: (a) 10 AWG, 40A

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 cur-rent, 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 incor-porates more than one hermetic refrigerant motor-compres-sor, 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:

Figure 440–5


440.32 Air-Conditioning and Refrigeration Equipment

440.33 conductor size for several Motor-compres-sors. Conductors that supply several motor-compressors must have an ampacity not less than 125 percent of the high-est 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 conDItIonersThe requirements in this Part apply to a cord-and-plug-con-nected 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 con-ductors for a cord-and-plug-connected room air conditioner must have an ampacity not less than 125 percent of the rated-load currents [440.32].

(B) Separate Circuit. Where the room air conditioner is the only load on a circuit, the marked rating of the air condi-tioner 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-and-plug-connected room air conditioner must not exceed 50 per-cent 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 fl oor, or

(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].

Question: What size conductor and overcurrent device are required for an 18A motor compressor? Figure 440–6

(a) 12 AWG, 30A (b) 10 AWG, 50A(c) a or b (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 cur-rent, 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

Author’s Comment: A 30A or 40A overcurrent device is permit-ted to protect a 12 AWG conductor for an air-conditioning circuit. See 240.4(G) for details.

Figure 440–6


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-and-plug-connected room air conditioners must be provided with a factory-installed leakage current detector, or with an arc-fault circuit-interrupter (AFCI).

Figure 440–7

Figure 440–8


Article 440 Practice QuestionsA

RTI

CLE

440 Practice Questions4. Branch-circuit conductors supplying a single a/c motor-

compressor 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.

(a) 100(b) 125(c) 150(d) 200

5. An attachment plug and receptacle can serve as the disconnecting means for a single-phase room air condi-tioner 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 lo cation within sight from the room air conditioner

(c) a or b(d) a and b

artIcLe 440. aIr-conDItIonIng anD reFrIgeratIng eQUIPMent—PractIce QUestIons1. Article 440 applies to electric motor-driven air-condi-

tioning and refrigerating equipment that has a hermetic refrigerant motor-compressor.

(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

3. 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.

(a) with(b) without(c) with or without(d) none of these

Answers:1. (a) 440.12. (d) 440.3(C)3. (c) 440.14 Ex 14. (b) 440.325. (c) 440.63

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