Dead circuits with breakers across from each other


A couple of tests would prove useful...

Test for voltage with a multimeter at the breaker. With the breaker reset to "on", there should be 110 volts between the hot lead of the circuit breaker and the neutral bus bar. If there is less than 110 volts, swap out the breaker with a "known-good" breaker, then test again.

Once you know the breaker itself is good, check the voltage at each of the devices. If you have 110 volts between hot and ground, but no volts between hot and neutral, then you know you are looking for an open neutral condition. If you have an open neutral, you can narrow things down a bit with another test: TURN THE BREAKER OFF, then test for continuity between neutral and ground at each device. Because neutral and ground are bonded together at the main panel, there should be continuity between neutral and ground at each device.

If you have no volts between hot and neutral, then you have an open hot condition.

By-the-way, we have...

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Two months ago, the kitchen lights were flickering. I realized the kitchen lights and outlets were connected to a single breaker. I measured the voltage and it spiked from 5v - 120v intermittently. I replaced the breaker (Murray 15A single-pole #MP115) and all was well.

Three days ago, the same kitchen lights started flickering again. The breaker read at 102v - 105v which is well below the expected 120v. I flipped the breaker multiple times and measured voltage and different times of the day, but it was always consistently 102-105v. I replaced the breaker today and all is well once again.

Both breakers that were replaced did not look or smell burnt. Any idea why this happened? Could it just be the breaker I replaced two months ago was also a bad breaker? A friend suggested a current surge through the wires, but my assumption is if there was a current surge, the breaker would have tripped or burnt out instead of having a low voltage reading of 102v-105v.


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Various routine tests are performed for ensuring the quality, performance of a

circuit breaker

and these are

Power frequency over voltage withstand test Dielectric test on auxiliary circuit and control circuit Measurement of resistance of main circuit or contact resistance test Tightness test or SF6 gas leakage test Design and visual checks Mechanical operation tests.

Let us discuss them one by one.

Power Frequency Over Voltage Withstand Test

The power system may experience different temporary power over


conditions may be due to sudden cut of load from the system, wrong operation of online tap changer, insufficient shunt compensation in the system, etc. Power frequency over voltage withstand test of circuit breaker is performed to verify sufficiency of insulation strength of the main circuit to withstand this kind of abnormal over voltage conditions of the system. The circuit breaker should also be designed to be capable of...

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AC switchboards

If voltages exceed 250 volts d.c. or 55 volts A.C. then the switchboard must be dead front (no exposed live parts at the front) of the metal clad type.

Bus bars

High conductivity copper rated to withstand the thermal and electromagnetic forces which would arise in the event of a short circuit at the bus bars with all the generators in parallel. The bus bars will withstand these conditions for the length of time it takes for the alternator circuit breakers to trip or back up fuse to blow.

Certain instruments and controls require a feed direct from the bus bars. Any connection between the bus bars and protecting fuses must be capable of withstanding maximum fault level. Standard practice is to provide a three phase set of fuses, known as 'Back Up' fuses, as near to the bus bars as possible. Connections are then led to the racks of the many instruments fuses fitted.

Circuit breakers

Must be capable of making...

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There is a circuit in my house which has become unpowered, but I can't find a breaker for it. None of the breakers in the service panel are tripped (yes, I know what that looks like), and the two labelled "not in use" don't affect this unpowered line (I've cycled them both a couple of times).

The circuit has two GFCI outlets on it; both are unpowered and the TEST buttons have no effect (I've tried RESET, of course). The circuit also has an overhead fluorescent panel, and an outside security light, neither of which are working.

I thought I could use a circuit tracer (a.k.a. breaker finder) for this, but what I've read so far indicates that they only work on active lines (i.e., so you know which breaker to turn off).

Does anyone have a non-obvious suggestion for how I can find where this circuit is turned off? Or could I use a circuit tracer for this, even though it's unpowered?

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Circuit Breakers & Tripping

A circuit breaker can appear to be on, but really be tripped.

A breaker trips much more often for a real short than from some defect in itself.

GFIs and breakers are not usually the bad guy - they trip for a reason. And if your problem would make sense from their tripping but they DIDN'T, something other than them is probably at fault.

In some cases a circuit breaker will trip off only after the circuit has been running things for several minutes. This may not be from an overload but from a poor connection point at, or in, the breaker itself, which develops heat that fools the breaker.


A normal receptacle is sometimes ground-fault protected from elsewhere.

A GFCI receptacle will not trip for an overload.

A GFCI rarely trips from a defect in it. Usually a GFI trips from being miswired or from a fault in something that is plugged into it or into a regular outlet...

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Cold Weather Operating Problems with SF6 Circuit Breakers

Cold Weather Operating Problems with SF6 Circuit Breakers

IEEE Standards

ANSI/IEEE C37.04-19791 and ANSI/IEEE C37.010-19792 are the standards relating to the rating structure and application of circuit breakers. There is no specific advice concerning low temperature. The standard service conditions are covered in C37.041, which includes altitude less than 1000m, and a temperature range of -30°C to +40°C. Other features are covered as well, from seismic to frequency. There is reference in C37. to low temperature as an unusual operating condition. And -60°C certainly is unusual.

SF6 Circuit Breakers and SF6 Basics

SF6 has unique properties which render SF6 a nearly ideal media for arc interruption and dielectric strength. The dielectric strength is greater than any other known media at the same density. The reason lies in the relatively large physical size and mass. The...

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This article describes field failure reports of Zinsco or Sylvania-Zinsco or Kearney electrical panels: overheating, failure to trip, fires, other defects.

We [J Simmons] see damage in about 25% of the Zinsco/Sylvania panels that are checked. The problem occurs mostly on circuit breakers feeding circuits that have a steady heavy load on them (like heaters, hot water tank, dryer), and on circuits that are often overloaded such as circuits that supply the kitchen or bathroom.

In houses with Zinsco/Sylvania electrical panels and circuit breakers, I [Simmons] have tested these circuits with up to 30 amps on a 20 amp circuit breaker.

Green links show where you are. © Copyright 2017, All Rights Reserved.

The Zinsco circuit breaker will carry the overload for a long time without tripping. This...

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Engineering Guides

Becoming the good electrical engineer requires a lot of passion, training and commitment. This comprehensive section is prepared as a resource for individuals and professionals interested in the electrical engineering career path.

In this section you will find very usefull books and guides related to electrical science in general, AC/DC electrical circuits, network protection, electrical installations, lighting etc.

Power Substation

Substation engineers nowdays are involved in projects from design and conceptualization to maintenance. Because of the wide range of industries using electrical engineers, many engineers specialize in some of the sub-discipline of electrical engineering.

Depending on background and expertise, projects can include systems such as energy transmission and distribution, protection and control etc.

MS Excel Spreadsheets (XLS, XLSX)

This section is dedicated to tools every electrical...

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General information

Electrical motors operate on the principle that two magnetic fields within certain prescribed areas react upon each other. All electric motors use electromagnetic fields to create torque. For many motion engineers, motor selection plays a central part in getting good device performance. Knowing which motor to use in a given application improves the cost, performance, and simplicity of your machine-design process.There are many different electrical motor types, all with their good and bad sidex. Motion control is the art and science of precisely controlling the position, velocity, and torque of a mechanical drive. Motion-control systems comprise a numerical controller that performs path generation, such as a DSP; an amplifier; and a motor. Positioning-control systems most often employ step motors, dc-brush motors, and brushless-dc (permanent-magnet) motors. - an automation and control site with a large discussion area, and...
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