The Electrical Code

220.51 Fixed Electric Space Heating. In this one we are looking at FIXED SPACE HEATERS. Hwy am I shouting you may ask. Well because heaters that go under a desk are not fixed even if they require 100% of the load that the name plate is requesting. I have never worked on systems that work intermittently and talk to each other. But of course it must be out there in some type of commercial space. So for our conversation in this article we need will be referring to a space heater in the bathroom or an unheated space that needs it. At any rate, space heaters use induction to heat coils which inter heats the space through forced air or through convection. They draw 100% of the name plate amps, even if there is a fan motor. This motor usually draws a minimal amount of amps, usually milliamps. I would run a 20 amp circuit for this application even if the device calls for a 15 amp circuit. The demand might not need 15 amps to operate and the 14 gauge is rated at 15 amps failure happens at he weakest link in the circuit. Ok enough of my dialogue. See you on the next one.

“Fixed electric space heating loads shall be calculated at 100 percent of the total connected load. However, in no case shall a feeder or service load current rating be less than the rating of the largest branch circuit supplied.

Exception: Where reduced loading of the conductors results from units operating on duty cycle, intermittently, or from all units not operating at the same time, the authority having jurisdiction may grant permission for feeder and service conductors to have an ampacity less than 100 percent, provided the conductors have an ampacity for the load so determined.”