How to Prevent Breaker from Tripping

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duttonbrown

Lighting Designer
Location
Minneapolis, MN, USA
Occupation
Product Engineer, Lighting Designer
Hello,

I have a lighting design shop in an older space with one 20A supply for the space. We test fixtures to repair them, and on occasion, we trip a breaker when there is an unforeseen loose wire.

Is there any sort of device that can be used between a wall outlet and the plug for the product we are testing that will trip at a lower amperage so that I can avoid needing to contact maintenance to flip the breakers?

We were told previously to install GFCI's, which we did, and those have tripped a couple of times but not every time. What is the appropriate device to use? Or do we need to have a new line run down to our testing area with its own breaker?

Thank you so much for any help.
 
a good tool for any electrical testing is a variac. other than that, have maintenance install a over current device in your unit.
 
A gfci is not the answer. Is you install a fuse in line with the circuit then it is more certain the fuse will trip before the breaker. Best answer is to get a larger wire to your space and add a small panel
 
Power strips often have a 15 amp or less overcurrent device built in. If that would be enought for your test purposes. They reset just like a breaker.
 
ActionDave said:
Circuit on the test bench at our shop is on a 50A breaker.
Click to expand...

With a dead short from a loose wire the idea is for the breaker to trip as soon as possible so as to not damage the equipment. I wouldn't want a 50 amp breaker for testing anything that didn't need that much power.
 
Test fixtures with an ohmmeter or megger before plugging them in.
Make a test box with a 5-amp fuse and a 5-ohm resistor, and plug fixtures into that.
Best of all, if it's worth a couple hundred dollars: A test box containing a Variac (variable autotransformer), an ammeter & voltmeter, and a 5-amp fuse & 5-ohm resistor.
 
What type breakers are in your existing panel?

For instance, if it is a GE panel with GE breakers, you could put a box with a 15A sqD QO breaker on the bench, it will trip before a GE breaker does.

Pull up the IsquaredT trip curves for your existing breaker, find a mag trip breaker with faster trip time curves and put one of those on your bench.
 
Or you could just duct tape the breaker handle in the "on" position...

Yes, it's after 4PM on a Friday afternoon, and the beer is calling to me. :D
 
ggunn said:
Or you could just duct tape the breaker handle in the "on" position...

Yes, it's after 4PM on a Friday afternoon, and the beer is calling to me. :D
Click to expand...
Otherwise you would know that you have to use electrical tape instead of duct tape and you have to open up the case of the breaker to disable the trip-free feature. :lol:
 
I would suggest a fuse also. You CV would GH o with an Edison base type or those tubular AGC fuses. Fuses would work well for overloads because of the choice a ratings available. But I would assume that your trips are as result of faults though. Fuses would work well with low level faults and arcing faults but bolted faults would be pot luck as.there is no assurance that the peak would not also be seen by that breaker causing it to trip. But a bolted fauld is fairly unlikely to happen..
 
junkhound said:
What type breakers are in your existing panel?

For instance, if it is a GE panel with GE breakers, you could put a box with a 15A sqD QO breaker on the bench, it will trip before a GE breaker does.

Pull up the IsquaredT trip curves for your existing breaker, find a mag trip breaker with faster trip time curves and put one of those on your bench.
Click to expand...

If you are just working with low amperage 120 volts, you could wire in series an Edison base utility light fixture with a 100 watt incandescent light bulb. (three prong male on one end receptacle or terminals on the other) to test the fixture for shorts.
If it's a dead short the light bulb will shine at full brilliance if no shorts the light bulb will not light providing that the lamp you are testing has no load on it.
 
junkhound said:
What type breakers are in your existing panel?

For instance, if it is a GE panel with GE breakers, you could put a box with a 15A sqD QO breaker on the bench, it will trip before a GE breaker does.

Pull up the IsquaredT trip curves for your existing breaker, find a mag trip breaker with faster trip time curves and put one of those on your bench.
Click to expand...

ptonsparky said:
Run a feeder to your area with a larger capacity and install smaller CBs at your test area as suggested. Hard to imagine you're allowed to test and repair fixtures but you need someone else to reset the CB.
Click to expand...
One needs to look at trip curves of the local device as well as the upstream device. Seen short circuit/ground faults on 15/20 amp QO breakers that still trip a 60-100 amp QO feeder breaker upstream. Knowing the available fault current also helps determine how much current levels can reach when looking at those trip curves.
 
Trip curves are your best bet as others have said. When 100s or thousands of amps are flowing its a competition between the upstream and down stream breakers on who will trip first if not both.
 
templdl said:
... Fuses would work well with low level faults and arcing faults but bolted faults would be pot luck as.there is no assurance that the peak would not also be seen by that breaker causing it to trip. ...
Click to expand...
That's why I suggested a 5-ohm resistor. It's a low-enough impedance that a fixture will light up if all's well, but it'll limit the peak current in a bolted fault to 24 amps--more than enough to blow a 5-amp fuse, and low enough that the 20-amp breaker will remain closed long enough for the fuse to blow.
 
drcampbell said:
That's why I suggested a 5-ohm resistor. It's a low-enough impedance that a fixture will light up if all's well, but it'll limit the peak current in a bolted fault to 24 amps--more than enough to blow a 5-amp fuse, and low enough that the 20-amp breaker will remain closed long enough for the fuse to blow.
Click to expand...

There is such a device ?
It's known in the trade as a "short lamp"
In essence you wire a 150w incandesant light bulb in series
with what ever your testing.
If all is well and there are no shorts
then the lamp may glow a little bit depending on the load.
But if something goes wrong such as a short circuit
then the lamp will glow brightly limiting the current thru it.
And no blown breakers.

A very similaur approach.
I use these short lamps regularly
when testing unknown condition equipment.
saves a lot of money in fuses alone.
 
dmxtothemax said:
There is such a device ?
It's known in the trade as a "short lamp"
In essence you wire a 150w incandesant light bulb in series
with what ever your testing.
If all is well and there are no shorts
then the lamp may glow a little bit depending on the load.
But if something goes wrong such as a short circuit
then the lamp will glow brightly limiting the current thru it.
And no blown breakers.

A very similaur approach.
I use these short lamps regularly
when testing unknown condition equipment.
saves a lot of money in fuses alone.
Click to expand...

I use this technique in an industrial setting when troubleshooting intermittent control fuse "shorts". On many older PLC systems there will be a single 5 amp control fuse controlling field sensors, there will be a short that is intermittent in nature or hard to find. In these situations I use a 500 watt quartz lamp in series with the 5 amp control fuse. This will keep the 5 amp fuse from failing when there is a short. Then I use an amp clamp to find which of the 20 or so conduits leaving the control cabinet that has the short in its run (the short will be somewhere around 4 amps). It's a simple matter to clamp groups of wire until you find the "magic" 4 amp load leaving the cabinet.
 
dmxtothemax said:
There is such a device ?
It's known in the trade as a "short lamp"
In essence you wire a 150w incandesant light bulb in series
with what ever your testing.
If all is well and there are no shorts
then the lamp may glow a little bit depending on the load.
But if something goes wrong such as a short circuit
then the lamp will glow brightly limiting the current thru it.
And no blown breakers.

A very similaur approach.
I use these short lamps regularly
when testing unknown condition equipment.
saves a lot of money in fuses alone.
Click to expand...

Great idea!
I use this technique when chasing out short circuits in a residence.
 
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