Questions tagged [circuit-breaker]

For questions generally relating to safety devices used to automatically stop the flow of electric current in the event of a fault condition. Use this tag for questions about fuses, too.

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39
votes
2answers
11k views

How did a circuit that was shut off at the breaker almost kill me?

I just had a near-disaster while trying to install new smoke detectors. My house has AC hardwire connections for the smoke detectors. I wasn't sure which circuit the smoke detector AC connection was ...
27
votes
4answers
145k views

Should all Federal Pacific panels be replaced?

I understand that Federal Panel Stab Lok breakers have the potential for becoming stuck, overheating, and starting fires. My home has a Federal Pacific panel but no outward markings of being a Stab ...
26
votes
7answers
5k views

How can I add an ammeter and/or voltmeter to my home breaker panel?

In my professional life, I work in datacenters and all of our PDUs have ammeter displays on them. Of course they do: we always want to know how many amps a PDU is using. But in my house, nobody has ...
23
votes
13answers
33k views

What items in a house can potentially be damaged by shutting them off at the circuit breaker?

Are there certain items in a house (anything from a computer to a furnace) that can be damaged by shutting off its circuit at the electrical panel? If so, must one avoid turning off that circuit at ...
23
votes
4answers
9k views

Why would two circuit breakers be connected inside the service panel?

I was trying to locate the circuit breaker for an outlet in my garage and found a truly baffling setup. Two breakers control the same outlet (both plugs). After some head scratching, I opened the ...
22
votes
2answers
5k views

Is this correct? Welder suggests 15A outlet on 20A breaker, or 20A outlet on 30A breaker

I just bought a lower-mid priced 120V/20A welder (Forney Easy Weld 140MP), and the manual details that the welder be plugged into a 20A outlet (with a 30A circuit breaker), or you can use a provided ...
22
votes
13answers
125k views

What is simplest strategy to map circuits to breakers in the panel?

My breaker box is very poorly labeled and I want to figure out which circuits may have overloaded (or close to it) and which could reasonably handle a little more. In the past I have just tried ...
22
votes
1answer
6k views

240v Outlet with 120v and 215v - How?

Ok this is a weird one and maybe I just don't understand how mains work (though I feel I have a good enough knowledge to stay safe and do basic breaker work & wiring). Buddy moved into a new shop ...
21
votes
5answers
2k views

subpanel breaker tripped as well as main breaker - should I be concerned?

All... My garage had only one outlet so I extended it using surface raceways. Like a dummy, I did not turn off the breaker when I started the installation of the raceway. "I know what I'm doing ...
20
votes
2answers
13k views

What danger/code violation is oversized breakers?

I just got the results of a home inspection where they claim there is mismatched breakers and wires in my electrical panel. Specifically, the range (40A breaker) and heat pump (50A). He claims the ...
20
votes
4answers
4k views

What should I do with a powered switch that seemingly does nothing?

In my house, I fortunately have a well-labeled circuit breaker. There are a few rooms that could be better named, but it's fine. As such, it's very easy to identify almost every switch and what it ...
20
votes
8answers
28k views

Is there a lifetime failure count for a breaker?

I have an external cutoff for my air conditioner that has two physical fuses (TR-50's, time delay 50 amps) outside. This is between the condenser unit and the main power panel, where it is protected ...
20
votes
5answers
214k views

What are the differences between SDS, SDS Plus, and SDS Max drills?

Basically I had to use a breaker last weekend, it was clear I did not need the “heavy duty” as I did not have 6” of solid concrete, but the descriptions of the other options confused me.
19
votes
6answers
3k views

How can I calculate my anticipated peak current load?

Preamble This question takes place in Japan. In Japan, domestic electrical service is metered, but there is also a monthly fee that increases with larger service capacity. Units are wired for (...
16
votes
4answers
8k views

Can I run a 15A table saw on a 15A circuit if there are also shop lights on the same circuit?

I apologize if this is a tired question, but none of the other similar questions I found are close enough to what I really need to know. I am hoping to buy a DeWalt table saw for use in my garage. The ...
16
votes
3answers
6k views

What is the difference between a "handle tie" and "common trip" in circuit breakers?

This image shows a quad-breaker with handle ties. Image borrowed from this DIY question One of the comments noted that despite the "handle ties", this is not a "common trip" ...
16
votes
3answers
91k views

What is electrical code for number of wires in a breaker?

US, Georgia I am adding some new ciruits to add some additional outlets. The closest place is to run a wire to the main panel box. My question is, can I connect more than one wire to a breaker and ...
15
votes
4answers
10k views

GFI outlets tripped after power outage

I live in a rural area that has frequent power outages (Several per month. Less than a minute in duration). When the power is restored, several GFI outlets always trip. I am trying to track down ...
15
votes
3answers
6k views

Condensor went, HVAC guy is blaming electrician, is this possible?

My brand new HVAC unit, the condensor died. The unit has a sticker that says the following: Minimum Circuit Ampacity 32 amps Max Fuse / Breaker 50 The electrician ran a 8 gauge wire with a 40 ...
15
votes
2answers
37k views

Splitting a 240V line into two 120V lines

In my garage I have wiring for a 240V outlet. It is a four-wire setup (two hots, one neutral and one ground). It is set up on a 20 ampere double breaker in the circuit breaker box. I want to remove ...
14
votes
6answers
27k views

Breakers loose in main panel, does whole panel need to be replaced?

I went on a breaker flipping binge the other day because the panel at my house wasn't labeled and I had a doorbell transformer to replace. After I got the doorbell finished I realized the fridge wasn'...
14
votes
3answers
4k views

Why did my leaking pool light trip the circuit breaker, but not the GFCI?

This is, I am sure, an extremely naive question. I hope that's okay (and I hope it can be answered at a level I'll understand). The background: My swimming pool has underwater light fixtures, on ...
14
votes
1answer
2k views

Safety hook on double pole circuit breakers

My home was built two years ago, so I would expect everything to have been done up to code. The problem is that I don't know what the metal ring in this photo is. It loops over the double pole circuit ...
14
votes
5answers
4k views

I tripped a 20amp breaker but didn't feel a shock - why?

I was stripping a hot ungrounded conductor while a 20A breaker was on by accident. When my wire strippers pierced the sheathing, a large spark blew out and tripped a breaker, but yet I felt nothing. ...
13
votes
1answer
2k views

Why does a USA/Canada surge-protected extension lead (110V) trip my circuit breakers in the UK (220V)?

I moved from Canada to the UK and for convenience I would like to use some of my Canadian aquired extension leads (for light power items such as ethernet switches). Problem is that the surge-...
13
votes
1answer
4k views

Why are adjacent breakers for unrelated circuits ganged?

I'm looking at electric panels in some newer residences and seeing something confusing: Circuit breakers that are adjacent to each other, but that cover unrelated circuits, are ganged, as shown below. ...
13
votes
4answers
2k views

GFCI Breaker - Good or Bad?

I have a GFCI circuit (GFCI breaker in the breaker box). If I attempt to test this circuit by plugging in my GFI Tester into a standard outlet that is on this GFCI circuit, the GFI Tester lights ...
12
votes
5answers
30k views

Does turning circuit breakers off cause wear?

A comment over on another SE got me thinking. With screw-in fuses, unscrewing it and then later screwing it back in causes negligible wear on either part of the installation. But what about modern "...
12
votes
6answers
199k views

How do I add more circuit breakers once the breaker box is full?

My house was completely rewired by the previous owner. They tore out all the old knob-and-tube and replaced it with modern wiring. I definitely appreciate this, but unfortunately they left ...
12
votes
2answers
2k views

What are these fuses?

Just come across a fuse box that I've never seen before. The box looks like this: They are like light-bulb-type things that host a fuse inside of them. The fuse looks like this: They work ...
12
votes
6answers
27k views

Why would there be a 50 amp plug on a 30 amp appliance?

I have an old conveyor dryer, which my office purchased used some time ago, just sitting in storage. The dryer is for silk screen t-shirts and has a large heating element and a variable speed conveyor ...
11
votes
3answers
3k views

Why would an air conditioning unit specify a maximum breaker size?

A ductless mini split unit I am interested in specifies a maximum breaker size of 15 amps. Why would this be the case? The unit is going to be installed on the opposite side of the house from where ...
11
votes
3answers
2k views

Can someone explain how this makes sense electrically?

The wiring in my house is... odd. Nearly every pair of outlets has one of the outlets connected to a light switch. Sometimes that switch is quite far from the outlet even when there are other closer ...
11
votes
1answer
2k views

What is this metal thing on my circuit breaker

Just bought a condo and one of the breakers in it has this metal thingy on it. What is it? What is it for?
11
votes
3answers
60k views

How can I determine which outlets belong to which circuit?

I'm putting in a powerline Internet adapter for my house (something like this). My mom said it has two circuit breakers, but she has no idea how the house is divided between them. Going across ...
11
votes
1answer
117k views

Why is my air conditioner tripping the circuit breaker?

Our air conditioner recently stopped blowing out cold air. When I went to check on it, I noticed that the outside unit wasn't coming on. We had had problems with ants in the contacter in the past, ...
10
votes
4answers
7k views

20 Amp single receptacle on two 15 amp breakers?

I bought a new Master Blaster that draws 18 amps when using both of its motors that I intend to use to when washing/detailing my car. In my garage, I currently don’t have a 20 amp outlet. I have two ...
10
votes
1answer
2k views

Can I swap out this 20A breaker for a 15A breaker?

I'm wiring my shed. There is a sub panel out back with a 20A breaker that supplies power to my pool light. I tapped that line to run the power to my shed because it's already ran about 3/4 of the ...
10
votes
2answers
2k views

New house generator AC breaker tripping

I have been in our new house less than 1 year. Yesterday we had a a prolong power outage so I decided to test the generator I got for hurricane season to the house existing generator inlet. I turned ...
10
votes
4answers
23k views

Is it safe to use two single-pole breakers for a 240 V circuit?

I recently had an electrician come out and replace my electric panel. He seemed very knowledgeable and overall appears to have done a good job, even went through and labelled most of the panel... ...
10
votes
2answers
4k views

Tandem breaker needs both thrown to break circuit. Incorrectly wired?

I have a tandem circuit breaker in my main breaker box with two 20 amp breakers. To turn off power my wife's office, I need to throw both breakers. I can throw either one and as long as the other is ...
10
votes
1answer
76k views

How can I determine circuit breaker requirements for an electric range?

I recently had a new range installed and when an electrician was visiting, he pointed out that the circuit was over capacity because the range was rated at 12.2KW at 240V. He said 12,200 W / 240 V = ...
10
votes
6answers
22k views

Why does my microwave keep throwing the circuit breaker?

I have a circuit that powers several things in my house: Kitchen microwave Basement lights Basement sockets Sump pump Recently, this circuit has been thrown with alarming frequency when I use the ...
9
votes
4answers
5k views

Kitchen rewire gone wrong

We're renovating a hundred-year-old house that's been through several owners and has hodge-podge wiring. I've redone all the wiring from scratch in the rooms we've re-walled. Everything has gone well ...
9
votes
6answers
6k views

Using a heater and toaster oven trips the breaker. Can an electrician fix this?

Using a heater and a toaster oven together, both about 1500w each, trips the breaker. It seems both are on the same circuit. Moving either appliance to a different location is not really an option. ...
9
votes
4answers
2k views

How can I automatically disconnect a coffee maker and space heater without tripping the building's 20A circuit breaker?

My small office has a 20A breaker and we have to run a space heater in the winter or else we freeze to death. Whenever someone turns on the coffee maker, the office circuit breaker trips and everyone'...
9
votes
3answers
1k views

Can you use a 2 pole 2-slot wide breaker to provide 240V?

Forgive my ignorance in terminology, I am a computer engineer but not an electrician. The concepts make sense to me, but I don't know all the industry standards and jargon. I recently had a 240V ...
9
votes
4answers
3k views

Can I run 275ft underground cable to pole barn?

I have a new 1500 sqft pole barn that needs electric. I expect to need 100Amp service at the barn which will have a 220V 15A compressor and 220V 25A welder. The rest of the barn will be 110V ...
9
votes
3answers
2k views

Running electrical to a shed

I have a shed in my backyard about 200ft from the house. I would like to run electrical to the shed to install 2 or 3 power outlets, and two LED lights for the inside. Currently from the house to ...
9
votes
1answer
125k views

Why did my electric range wiring burn out at the terminal block?

Turned on our 2 year old stove (Whirlpool Gold) and heard fizzing noises, then smelled electrical burning. Went downstairs and shut off the breaker (40 amp). That was the only way to get it to stop "...

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