Environmental conditions of residential electrical connections

2019

IEEE Access

The experimental results are presented for minimum trip current as a function of temperature for residential circuit breakers. These are often installed in enclosures that are exposed to seasonal temperature extremes. The trip current of these thermally actuated breakers is inversely related to temperature. The relationship is shown to be linear and it varies as much as 2:1 between brands. The trip current at extremely high and low temperatures can be estimated. At low outside ambient temperature the worst case 15 A breakers will not trip at 25 A, which would be the current load of two 1500 W portable heaters plugged into the same 15 A circuit. The diminished overcurrent protection at low temperature may be a factor that contributes to the elevated incidence of residential electrical fires during winter months.INDEX TERMS Breaker, circuit breaker, electrical fire safety, fire investigation, load center, outdoor, residential, temperature, test data, test method, testing.

“…Some are installed in unheated buildings. Many indoor breaker panels experience winter ambient temperature close to the outdoor ambient temperature [12].…”

Section: A Cold Temperature Operation and Fire Riskmentioning

confidence: 99%

Temperature Sensitivity of Residential Molded Case Circuit Breakers

2019

IEEE Access

“…H-M type breakers are expected to have relatively precise calibration that is independent of the wide ambient temperature range actually encountered in residential installations [11]. The first Brand 14 H-M failure was a 20 A breaker that tripped at 32.9 A (165% of rating) in its initial calibration test.…”

Section: B Brand 14 H-m Breakers: Repeated Calibration Testsmentioning

confidence: 99%

Faulty Residential Circuit Breakers—A Persistent Fire Safety Problem

IEEE Open J. Ind. Applicat.

2023

Circuit breakers for residential branch circuits must trip at or below 135% of rated current. A breaker that fails that requirement is defective. Samples of two brands, purchased from retail sources, are tested for that basic calibration. Both brands were tested 4 years ago. Previous samples of one brand were 50% defective, and new samples manufactured in 2021 are 28% defective. The second brand, previously defect-free, is again defect-free. The test results, past and present, imply that some manufacturers are calibrating breakers to trip too close to the allowable upper current limit, and are checking calibration by testing at higher current. The standard calibration test at 200% of rated current is shown to be incapable of indicating whether or not a breaker will trip properly, as required by the applicable standard, at 135% of rated current. A third brand tested came on the market recently. Its thermal-magnetic breakers trip correctly, but the brand's hydraulic-magnetic breakers are erratic, with 38% of the samples malfunctioning. The malfunctions are attributed to thermal distortion that causes mechanical binding of the triggering mechanism. Some breaker brands with a high defect rate have been in the distribution chain for many years and are permanently installed in homes. The increased risk of fire and injury for the occupants of these dwellings is significant. The long-standing history of this problem and the fire safety consequences are discussed.INDEX TERMS Circuit breaker, electrical fires, electrical safety, failure, fire, quality control, residential, risk, test data, test method, test results, testing.

“…Applied environmental conditions for most types of residential connections should include high humidity and elevated ambient temperature, related to unconditioned air, as occurs at connectors and wiring devices in perimeter walls of a home, unheated attic spaces, and some other residential locations [40]. This can be reasonably accomplished by testing in an unheated room with some ventilation to the outside, as was done in the previously mentioned CPSC tests, by sheltered outdoor exposure, or by a published standard method [41].…”

Section: E Testingmentioning

confidence: 99%

“…The conductor is one that passed the UL screening tests established in 1972, at the low-performance end of the relative ranking. The receptacles were then exposed for four months (September through December in Poughkeepsie, NY) to conditions representing installation in the perimeter wall of a building in an unheated room, in which the temperature and relative humidity are about the same as the outside ambient [40]. No current was applied other than for the time required for taking potential drop measurements at 15A current, and there was no insertion and withdrawal of attachment plugs.…”

Section: A Practical Examplementioning

confidence: 99%

Selection Criteria for Residential Aluminum Connections

2012 IEEE 58th Holm Conference on Electrical Contacts (Holm)

Lee

2012

Suitable permanent connectors are required for use with branch circuit aluminum wire in homes. Some connection devices that have been marketed as suitable for use with aluminum wire are prone to deteriorate with time under conditions of normal use, leading to instances of hazardous overheating. The literature and experimental evidence discussed in this paper soundly support the position that, from a safety standpoint, the only acceptable aluminum connection devices for permanent residential installation are those that show no resistance increase under both normal and accelerated test conditions.