While preparing a presentation, I noticed a photo taken at a facility where temporary power was needed periodically. The facility rented a generator when necessary. It showed a disconnecting means with four individual conductors stubbed out of the bottom of the enclosure.
A veteren electrician asked what the National Electrical Code (NEC) requirements are for installing cord-and-plug-connected room air conditioners. I thought the answer might be interesting to others.
Determining ampacity and rating
Article 110 Requirements for Electrical Installations; Article 210 Branch Circuits; Article 250 Grounding and Bonding; Article 314 Outlet, Device, and Pull and Junction Boxes, Fittings, and Handholes; Article 350 Liquidtight Flexible Metal Conduit: Type LFMC; Article 517 Health Care Facilities; Art
For the past few National Electrical Code (NEC) cycles, there has been a concentrated movement by parts of the construction industry to permit fire alarm cables, burglar alarm cables, communications cables and signaling system cables to be installed in a fabricated duct or plenum used for environme
An estimator asked what method to use to calculate the volt-amperes (VA) of a residence. He hoped to use the results as a guide to estimate the elements of the electrical system and wanted the standard method applied.
Article 210 Branch Circuits; Article 230 Services; Article 250 Grounding and Bonding; Article 366 Auxiliary Gutters; Article 422 Appliances; Article 517 Health Care Facilities; Various articles in Chapters 6, 7 and 8 are mentioned.
Many are aware that electrical equipment arcing and sparking -can cause chemical atmospheres (gases, vapors and dusts) to ignite. However, we often forget that thermal ignition of these chemical atmospheres also can occur if the chemicals are exposed to high temperatures.
There are two terms that seem to confuse designers. These terms are “diversity factor” and “demand factor.” To better understand the application of these terms when calculating the load for a service or a feeder supplying a facility, one must understand their meaning.
This article is a continuation of designing and installing electrical systems rated over 600 volts. Note that specific equipment as well as wiring methods and other items that form a complete high-voltage system are discussed.
Selecting switchgear—490.30 through 490.47
Article 110 Requirements for Electrical Installations; Article 250 Grounding and Bonding; Article 300 Wiring Methods; Article 517 Health Care Facilities; Article 547 Agricultural Buildings; Article 695 Fire Pumps; Some parts of the Guide Information for Electrical Equipment Directory (White Book) 20
A requirement for short-circuit current rating was added in the 2005 National Electrical Code (NEC) to Section 430.8 covering motor controller marking, to Section 440.4(B) covering controller marking for air conditioning and refrigerating equipment, and to 409.110 covering controller marking for ind