#2011 National Electric Code Code Development Costs#
#2011 National Electric Code Full Size Breakers#

2011 National Electric Code Code Development Costs

Today I'll set the record straight as to when tandem circuit breakers can be used. A double asterisk () at the beginning of an article identifies an amendment carried over from the 2011 edition of.Confusion abounds over the use of tandem circuit breakers in panelboards, even among electricians and electrical inspectors. Unfortunately, the NFPA intentionally makes this free online version difficult to find and use.Lined through type is deleted text from NEC. However, they do make available a limited-use online copy of the 2011 NEC. The NFPA recovers part of its code development costs by selling code books. The National Electric Code (NEC) is published by the National Fire Protection Association (NFPA).

Because of this, they're often referred to as 'cheaters.'Is this really 'cheating'? No, it's not. While a two-pole circuit breaker gets connected to two different poles at a panelboard and has a common trip or a handle tie for simultaneous disconnecting of two poles, a tandem breaker does not.The photo below shows a 60 amp two-pole circuit breaker at the top, then a 15 amp tandem circuit breaker (highlighted), then a 20 amp tandem circuit breaker (highlighted), then a 20 amp single-pole circuit breaker at the bottom.The next photo shows an older style tandem breaker found in Square D panelboards.Because tandem circuit breakers allow for two circuits to be installed on a panelboard in a one circuit breaker space, they're typically used after a panelboard has been filled to capacity with standard circuit breakers. You'll also hear them called duplex, slimline, twin, half-height, half-inch, double and wafer breakers, depending on local customs. A tandem circuit breaker is a double circuit breaker that takes up the space of a single circuit breaker on a panelboard. With the proliferation of sensitive electronic equipment such as computers, answering machines, microwaves, etc., higher-grade protection products were needed.Understand the most important 2011 National Electrical Code changes Course Outline / Agenda Properly installed and maintained electrical systems are a crucial part of day-to-day operations for any building, plant or piece of equipment.First, a quick definition. From inception, lighting/surge arrestors have been addressed, now detailed in Article 280 of the Code.

G 3040BL1200 = 30 spaces, 40 total circuits allowed. The model of the panelboardThe model or part number of the electric panelboard usually will indicate whether or not the electric panelboard is designed to accept tandem breakers and how many can be used. The difficulty for home inspectors is that the marking is not usually visible after installation, and home inspectors aren't supposed to pull out circuit breakers to try to figure this stuff out.Now that I’ve talked about the general rules for tandem circuit breakers, I’ll discuss the ways that home inspectors or electrical inspectors can determine when tandem circuit breakers are allowed in various panelboards. As clearly indicated by the label on the side of the circuit breaker pictured below, these circuit breakers are not allowed in ClassCTLpanelboards. Non-Class CTL tandem circuit breakers do not have the ‘rejection’ feature that Class CTL breakers have. This is probably where the term 'cheater' comes from.For panelboards manufactured before adoption of the Class CTL standard, non-Class CTL tandem circuit breakers are allowed to be installed as replacement circuit breakers only.

BR 1220B100 = 12 spaces, 20 total circuits allowed. Tandem circuit breakers are not allowed. G 3030BL1150 = 30 spaces, 30 total circuits allowed.

HOMC 20U100C = 20 spaces, 20 total circuits allowed. Tandem circuit breakers are not allowed. BR 1212B100 = 12 spaces, 12 total circuits allowed.

2011 National Electric Code Full Size Breakers

This panelboard has 20 full-size spaces, so tandem circuit breakers aren’t allowed.What's the concern with tandem circuit breakers?When tandem circuit breakers are used in locations where they're not allowed, they could make an improper physical connection to the bus bar in the panelboard, which can create a fire hazard. In the photo below, you can see that only 20 circuits are allowed at the panelboard. A diagram inside the panelboardThe wiring diagram inside the panelboard is a great way to determine if tandem breakers are allowed and, if so, exactly where they're allowed. In the photo below, you can see that the top four spaces allow only full size breakers, while the bottom eight slots allow tandem breakers.Here’s another panelboard diagram – this panelboard allows the use of tandem breakers in four locations.And another – this panelboard doesn’t allow any tandem breakers.And another – this panelboard allows tandem breakers in the bottom ten spaces only (11-20 and 31-40).Another easy thing to look for is a label stating the maximum number of circuits allowed.