Article 426: Fixed Outdoor Electric De-Icing and Snow-Melting Equipment

Article 426 Fixed Outdoor Electric De Icing and Snow Melting Equipment

I. General

426.1

Scope

This article covers installations both embedded and exposed.

426.2	Definitions
426.3	Application of Other Articles
426.4	Continuous Load

This is to be considered a continuous load.

II. Installation

426.10	General
426.11	Use
426.12	Thermal Protection

Must be protected against contact by persons if operated at temperatures above 60°C (140°F).

426.13

Identification

Warning signs must be posted where used.

426.14

Special Permission

 

III. Resistance Heating Elements

426.20

Embedded De-icing and Snow-Melting Equipment

Units cannot exceed 1300 watts/m2 (120 W per square foot) and must have at least 25 mm (1 in.) between cables. They can be installed either on an asphalt or masonry base at least 50 mm (2 in.) thick and covered with at least 38 mm (1½ in.) of asphalt or masonry, or on any approved type of base embedded in 90 mm (3½ in.) of asphalt or masonry and covered with at least 38 mm (1½ in.) of asphalt or masonry. They must be secured and not bridge expansion joints unless proper provisions are made.

426.21

Exposed De-icing and Snow-Melting Equipment

They must be secured, proper temperature limiting, and have no cross-bridge expansion joints unless provided for.

426.22	Installation of Nonheating Leads for Embedded Equipment
426.23	Installation of Nonheating Leads for Exposed Equipment
426.24	Electrical Connection
426.25	Marking
426.26	Corrosion Protection
426.27	Grounding Braid or Sheath
426.28	Equipment Protection

 

IV. Impedance Heating

426.30	Personnel Protection
426.31	Isolation Transformer
426.32	Voltage Limitations

The secondary winding of the isolation transformer must not operate at greater than 30 V ac unless protected by a ground fault circuit interrupter. If ground fault circuit interrupter is used it can be greater than 30 V but not more than 80 V.

426.33	Induced Currents
426.34	Grounding

 

V. Skin Effect Heating

426.40	Conductor Ampacity
426.41	Pull Boxes
426.42	Single Conductor in Enclosure
426.43	Corrosion Protection
426.44	Grounding

 

VI. Control and Protection

426.50

Disconnecting Means

Must have a disconnecting means that opens the ungrounded wires. The branch-circuit breaker can be used if readily accessible. Also permitted is a factory-installed attachment plug if it is rated not more than 20 A and 150 V to ground.

426.51

Controllers

If the temperature controller operates line current and has an off position, it must open all ungrounded conductors. It cannot be used as a disconnecting means unless it can be locked in the open position. If no off position is provided, it does not have to open all ungrounded conductors and cannot be used as a disconnecting means. If it controls a relay, it does not have to open all ungrounded conductors and cannot be used as a disconnecting means. There are also rules in the NEC® for combined switching devices.

426.52

Overcurrent Protection

Refer to Section 426.4.

426.54

Cord- and Plug-Connected De-icing and Snow Melting Equipment