More on amperage ratings for kilns

I’ve received some feedback from folks wanting more information about my previous post “The rule of 80% and kilns“.

First, here is a direct link to the NEC (National Electrical Code): http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=70 (scroll to near the bottom of the page and click on the link that says “View the 2008 edition of this document”)

The important sections are 210.21 and 210.23. In part, they say:

Table 210.21(B)(2) Maximum Cord-and-Plug-Connected Load to Receptacle

Circuit Rating …………………… Receptacle Rating ………………. Max Load (Amperage)
15 or 20 Amps ………………………. 15 Amps ……………………………… 12 Amps
20 Amps ………………………………. 20 Amps ……………………………… 16 Amps

210.23 Permissible Loads

(1) Cord-and-Plug-Connected Equipment Not Fastened in Place

The rating of any one cord-and-plug-connected utilization equipment not fastened in place shall not exceed 80 percent of the branch-circuit amperage rating.

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