Warm Lighting Circuit Breakers
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Warm Lighting Circuit Breakers
Tip written by: Infraspection Institute
When performing infrared inspections of branch circuit panels, lighting circuits will often appear warmer than adjacent circuits. If adjacent circuits are lightly loaded, the warmer circuits may be indicative of a normal condition or they may represent a more serious condition.
For electrical panels with single-phase branch circuits, is often quite normal for lighting circuit circuits to appear warmer as they frequently have some of the highest loads within the panel. To confirm this, load readings should be obtained with a true RMS ammeter to determine that the subject breakers are operating within specifications. For long term use, it is recommended that circuits operate at less than 80% of their rated capacity.
If lighting circuit breakers are used as switching devices, they must be rated as Switch Duty. Using non-switch-rated breakers can cause excess wear on the breaker contacts. To determine the integrity of breaker contacts, one should remove the breaker from service and perform a contact resistance test through the breaker with the breaker in the closed position. Such testing should be performed with a digital low resistance ohmmeter.
If lighting circuits have fluorescent fixtures or other solid state devices connected to them, the circuits are likely to contain significant harmonic content. To determine if significant harmonics are present, the subject circuit should be tested with a harmonics analyzer.
In lieu of testing a suspect breaker, you may wish to replace it with a new one and re-image the subject circuit to ascertain if the situation has improved.
Infrared inspections of power distribution systems is one of the many topics covered in the Level I Infraspection Institute Certified Infrared Thermographer® training course. For information on thermographer training including course locations and dates, visit us online at www.infraspection.com or call us at 609-239-4788.
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