National Electrical Code Top Ten Tips:
Article 426 -- De-icing and Snow-melting equipment
by Mark Lamendola
Based on the 2020 NEC
Please note, we do quote from copyrighted material. While the NFPA
does allow such quotes, it does so only for the purposes of education
regarding the National Electrical Code. This article is not a substitute
for the NEC.
These are the 10 NEC Article 426 items we deem most important, based
on the pervasiveness of confusion and the potential costs of same.
- It doesn't matter if these systems are embedded or exposed. If it's an
electrically energized heating system used for melting snow or ice and it's fixed in place outdoorrs, it must
comply with Article 426 [426.1].
- Article 426 recognizes three kinds of heating systems: Impedance,
resistance, and skin-effect [426.2].
- If you use any cord-and-plug de-icing and snow-melting equipment, it must also comply with Article
422. And it must be listed [426.54]
- Don't apply load diversity or similar factors to equipment covered by
Article 426. You must consider all such equipment to be a continuous load [426.4]. The NEC does not require you to put these on their own branch circuits, but good engineering practice does. Run outdoor receptacles, outdoor lights, and other kinds of loads on circuits not used for de-icing and snow-melting equipment.
- Keep protection as a foremost thought. Protect the equipment from damage [426.11],
and protect people from thermal burns and electric shock by using the proper
installation techniques [426.12]. The installation instructions that come with the units will describe the proper installation techniques, but also check the manufacturer's website for instructional videos.
- General requirements are in Part I [426.1 - 426.4].
- General installation requirements are in Part II [426.10 -14].
- You'll find the specific requirements for Resistance, Impedance, and
Skin-effect type elements in Parts III, IV, and V, respectively. While these
have similarities, don't apply the wrong Part to the system in question.
- Part VI, titled, "Control and Protection," is chiefly concerned with the
disconnecting means and controllers.
- Ensure your controllers conform to 426.51. Note that remote controlles cannot be used as the disconnecting means discussed in Part VI.