Article 440: Air Conditioning and Refrigerating Equipment

Article 440 Air Conditioning and Refrigerating Equipment

I. General

This section states the scope.

Many additional articles are listed, such as 422, 424, 430, 460, and 470, and some not in Chapter 4.

The rating on the nameplate is to be used for a hermetic refrigerant motor compressor. There are two exceptions. Conductors are to be chosen from Tables 310.16 through 310.19 or in accordance with Section 310.15. Requirements are noted for multimotor equipment.

A refrigerating system or air-conditioning system can be considered in accordance with Section 430.87, Exception, and Section 430.112, Exception.

II. Disconnecting Means

For hermetic refrigerant motor-compressor it must be at least 115% of the larger of the rated load or branch-circuit election circuit. There is an exception. If the rated load or locked rotor current comes out to be 100 hp or larger, use the provisions of Section 430.109(E). Information is given concerning equivalent horsepower and locked rotor current. Additional information is given concerning combination loads, horsepower rating, full load equivalent, small motor compressors and disconnecting means.

The separable connector or plug and receptacle can be used as the disconnecting means.

It must be within sight and readily accessible to the equipment. There are two exceptions.

III. Branch-Circuit Short-Circuit and Ground-Fault Protection

(A) Rating or Setting for Individual Motor-Compressor. It must allow the motor to start. The NEC® therefore permits a rating or setting of up to 175% of the larger of the motor load or branch-circuit selection current. This can be increased to 225% if necessary. A 15-A rating is the least that can be required for branch-circuit, short-circuit and ground-fault protection.

(B) Rating or Setting for Equipment. It must also allow the equipment to start. If only one hermetic refrigerant motor compressor is used, conform to Section 422(A). If more than one hermetic refrigerant motor compressor is used, conform to Section 430.53 and the following:

(1) If the hermetic refrigerant motor compressor is the largest load, use Section 440.22(A) for this plus the other loads.

(2) If the hermetic refrigerant motor compressor is not the largest load, the sum is that of the rating of the motor compressor loads plus the value noted in Section 430.53(C)(4) or Section 240.3 for other loads, whichever is applicable. There are two exceptions. For a detailed analysis, refer to the NEC® and one of the many reference guides.

(C) If a maximum rating is indicated by the manufacturer, it should not be exceeded.

IV. Branch-Circuit Conductors

The rating cannot be less than 125% of the largest of the motor compressor rated load or branch-circuit selection current. There is additional information concerning wye-start, delta-run motor compressor.

The ampacity must be the sum of the larger of the rated load or branch-circuit selection currents of all the motor-compressor loads plus full-load currents of the other motors plus 25% of the largest motor. There are two exceptions to this: one is for room air conditioners as per Part VII and the other is for interlocked motors.

The capacity must be adequate for all other loads, plus the motor-compressor load as specified in Sections 430.32 and 440.33. An exception is also made for interlocked circuitry.

It cannot be less than that marked on the equipment as per Section 440.4(B).

V. Controller for Motor-Compressors

Generally, use the nameplate ratings. If more than one load is served, use the combined load rating [refer to Section 440.12(B)]. There are additional requirements.

VI. Motor Compressor and Branch-Circuit Overload Protection

(A) Protection of Motor-Compressor. The following methods can be used: (1) an overload relay that will trip at not more than 140% of motor full-load current; (2) a thermal protector integral with the motor compressor; (3) a fuse or inverse time circuit breaker responsive to motor current and rated not more than 125% of motor current; and (4) a protective system furnished with the unit or specified for the unit.

(B) Protection of Motor-Compressor Control Apparatus and Branch-Circuit Conductors. It can be the same device protecting the motor-compressor in accordance with Section 440.52(A). There is an exception.

VII. Provisions for Room Air Conditioners

The branch circuit can have a load of only 80% of its rating for a cord- and plug-connected air-conditioning unit, if no other loads are on the circuit. If other loads are on the circuit, then the load of the cord- and plug-connected air-conditioning unit cannot be more than 50% of the rating of the branch circuit.

The attachment plug can be used for a single-phase unit at 250 Volts or less if the manual control on the unit is readily accessible and within 1.8 m (6 ft.) of the floor or if a manual disconnecting means is readily accessible within sight of the unit.

The length of the cord cannot be larger than 3 m (10 ft.) for 120 V or 1.8 m (6 ft.) for 208 to 240 V.

The following article titles are listed for reference: Article 445Generators; Article 450Transformers and Transformer Vaults (Including Secondary Ties); Article 455Phase Converters; Article 460Capacitors; Article 470Resistors and Reactors; Article 480Storage Batteries; Article 490Equipment, over 600 Volts, Nominal.