Arc Fault Circuit Interrupters (AFCIs) are an important electrical fire prevention and safety requirement of the National Electrical Code. With the changes to the NEC in 2017 there still seems to be questions regarding the use of AFCIs. This primer will address these questions.
In order to understand what a feeder is, it is best to start with what a feeder is not. The conductors between the utility service point and the service disconnecting means are service conductors, not feeder conductors. Special service conductor rules apply because these conductors do not have short-circuit or […]
Feeders Part 3 Feeder Conductor Ampacity. The conditions of use must be considered when determining the minimum size of a feeder conductor. A continuous load, such as the lighting load in a store building, generates heat in the feeder conductor that must be compensated for. Ambient temperatures above 86oF or more than […]
The general rule in 215.3 is that a feeder overcurrent device shall have a rating not less than the noncontinuous load plus 125% of any continuous loads supplied by the feeder. Unless permitted for specific applications, such as motor circuits, the rating of the feeder overcurrent device is selected as […]
A multiple-outlet branch circuit is a branch circuit that supplies two or more outlets. With the exception of the required small appliance, laundry, and bathroom receptacle circuits in dwelling units, those outlets may be a combination of lighting outlets for luminaires, receptacle outlets for cord and plug connected utilization equipment […]
If you are preparing to take an electrical licensing exam, you will need to know how to calculate the feeder or service load for a single family dwelling. Refer to section 220.82(A)&(B) in the 2014 National Electrical Code (NEC). Here is a sample problem. Use the optional calculation to find […]
The requirements for securing and supporting are similar in intent, but there are differences. Securing is done by installing a mechanical means of attachment to the cable and attaching it to a stationary structural member so the cable does not move. This will prevent the cable or conduit from becoming loose and pulling away from a box or fitting. Support requires a mechanical means to prevent the cable from sagging or drooping which may cause damage to the cable and create a hazard. A cable may remain loose while its support is maintained.
The 2014 NEC is clear about how cables and raceways must be supported. The general rule in 300.11(A) is that raceways, cable assemblies, boxes, cabinets and fittings shall be securely fastened in place. Cables cannot be used as a means of support for other cables, raceways, or nonelectrical equipment, per […]
Supply-Side grounded and bonding conductors are sized from Table 250.102(C)(1) in the 2014 NEC. In earlier Codes, all these conductors, as well as the Grounding Electrode Conductor, were selected from Table 250.66. Table 250.102(C)(1) from the 2014 NEC. It is very helpful to have a separate Table for selecting the […]
Properly sizing an SE cable installed in thermal insulation requires a careful examination of the Code. Section 338.10(B)(4)(a) is all about interior installations of SE cables and states: Where installed in thermal insulation the ampacity shall be in accordance with the 60°C (140°F) conductor temperature rating. The maximum conductor temperature […]