Why and How to Verify Circuit Breaker Settings

Why and How to Verify Circuit Breaker Settings

March 5

Checking breakers against a short circuit and coordination study is a crucial step to ensuring safe and efficient electrical systems.

Electrical problems are among the worst facility nightmares plaguing owners, managers, staff, and occupants. A professional electrical engineering team can help prevent these problems when a building is constructed or renovated. The short circuit and coordination study is a key tool for optimizing electrical system performance by verifying that circuit breakers are set to deliver the results specified in the project’s electrical design. Without the study in hand, it’s impossible to adequately verify breaker settings.
 
The staff responsible for checking the breakers—which could be members of the facility management team or an outside professional, such as a commissioning engineer—must compare the settings from the short circuit and coordination study with the breaker settings on-site. All breakers should match (or be adjusted to match) the study, unless a circuit breaker can’t meet the specified requirement.

If the breaker can’t be adjusted to match the study, the person in charge of breaker checks must document the problematic setting (it’s best to take a picture if possible). The information should be forwarded to the engineer of record to determine if a new breaker is required or if there’s an error in the study.
 
If circuit breaker settings aren’t verified against the study, and a breaker is set too low, nuisance trips are likely. More serious consequences may involve unplanned equipment shutdowns or unnecessary activations of emergency power systems. Conversely, if a breaker is set too high, equipment may not be adequately protected against surge or overload damage. This situation also increases the risk of a fire.
 
G/BA recently performed several projects highlighting the importance of a short circuit and coordination study, and the need to ensure that all breakers are set according to the study.
 
Project 1 involved an academic building being renovated at a major Northeastern university. G/BA’s staff and the electrical contractor were on site to verify 156 breakers against the short circuit and coordination study provided by the electrical system designer. Of these 156 breakers, 25 (17%) had to be corrected in the field. Forty-nine were flagged for further review and for possible corrections in the coordination study. Nine breakers were found in the field that weren’t even present in the study. Two breakers were missing arc flash labels. In all, about half the breakers evaluated needed some sort of adjustment or further review. This problematic situation would not have been uncovered without the procedure of checking the breaker settings against the study.
 
Project 2 was done in an academic lab being renovated to support cadaver studies and other medical education programs. G/BA met with the general and electrical contractors to review the 31 circuit breakers serving the space. In this case, only one breaker needed correction. But three were shown on the study as being fed from the wrong source, and two were found in the field that were not on the study. Clearly, even generally well-executed projects benefit from a check against the study.
 
Project 3 was done at a large new athletic facility for a major Midwestern university. G/BA, the electrical contractor, and an electrical testing firm all had staff present to verify breaker settings against the coordination study provided by the electrical design firm. Here, 91 breakers were checked and 15 were corrected in the field (16%) per the study. Three circuit breaker protection relays were found not to be working and had to be replaced to protect the equipment.
 
Project 4 concerned a new Midwestern hospital campus. This large facility includes 273 circuit breakers, which were checked by G/BA against the electrical engineer’s short circuit and coordination study. In this case, only 21 of the breakers had to be corrected per the study (8%). Two protection relays were malfunctioning and had to be replaced. Six breakers were shown on the study as being fed from the wrong source. Fixing these problems helped ensure that the hospital’s electrical systems would function properly, and that correct documentation would be available to the facility team going forward.
 
Though circuit breakers operate behind the scenes, and are often overlooked until something goes wrong, they remain a vital part of every building’s electrical infrastructure. By implementing an enhanced electrical commissioning process, G/BA's engineers have found that every project we review requires some level of correction. 
 
We recommend that facility owners and managers make sure electrical systems are protected by having all breakers checked against the short circuit and coordination study. G/BA can help with all aspects of preparing these studies, as well as field-verifying breakers and generating proper arc flash labeling.

Contact us with your questions and concerns.