Calling Electricians - adding a 20-amp circuit in garage

[MichaelD]

Thanks for the answer. What about something say under that amount, i.e. 12-13A. Will it occasionally draw more, and blow the fuse/trip the breaker as well? Or will that be ok in the socket?

It can happen but shouldn't if the breaker is in good condition. Breakers do go bad. A breaker that keeps tripping every time you turn something on (and you're not exceeding the amp-load for that entire circuit) is a bad breaker and should be replaced.

Remember that typically, every outlet in room is on the same breaker. So if you have a coffee maker in one outlet, a hair dryer in another outlet and then you try to plug in a vacuum cleaner to a third outlet, you'll probably exceed the lmits of that one breaker that controlls all three outlets.

This is where the term "dedicated circuit" comes from. A single breaker with a single outlet designed for one thing (typically one) that draws a lot of current, to be plugged in.

 

[skyking]

Thumbsup for random will it blend reference

 

[MichaelD]

Lots of smoke!

http://www.youtube.com/watch?v=T8GiuM-gABY&

Romexsmoke! Don't breathe this! :biggrin:

I will definitely try not to do that tonight or whenver I get around to this project! 😱

 

[edro]

Thanks for the answer. What about something say under that amount, i.e. 12-13A. Will it occasionally draw more, and blow the fuse/trip the breaker as well? Or will that be ok in the socket?

Heater elements (heaters, toasters, dryers, etc) and motors are usually the highest loads in a house.
Motors (drills, sweepers, etc) usually have a large inrush spike, so while the normal current draw is 10A, at start up it could be 50-100A for a very short time.

A resistive load of 15A will not trip a 15A breaker, no matter how long it is present.
The breaker's trip time is based on the amount of overcurrent and ambient temperature.
The breaker itself trips due to heat of the bimetallic elements inside.
Lets say you are running an electric drill for 5min. The breaker elements are warmed up, but haven't quite tripped yet. If you stop and start the drill again, it can trip the breaker more easily because of the insrush and the breaker elements are already warm.

Google images of "circuit breaker trip curve" to understand the relationship of overcurrent and trip time. It will probably amaze you. (they handle much higher than the rated current)

 

[imagoon]

Not to hijack your thread MichaelD, but I have a stupid question, as I know nothing about electricity. If you have a tool or appliance that draws 15A, and you plug it in a standard 15A socket, are you asking to blow a fuse or trip a circuit breaker?

Typically you don't want to run @ 100% load, so technically a 14.95amp load on a 15amp breaker is considered 'overloaded.' You do not want to be above 80% continuous or your breaker may start popping due to heat issues / spikes from other devices turning on and off etc.

 

[Rubycon]

Heater elements (heaters, toasters, dryers, etc) and motors are usually the highest loads in a house.
Motors (drills, sweepers, etc) usually have a large inrush spike, so while the normal current draw is 10A, at start up it could be 50-100A for a very short time.

A resistive load of 15A will not trip a 15A breaker, no matter how long it is present.
The breaker's trip time is based on the amount of overcurrent and ambient temperature.
The breaker itself trips due to heat of the bimetallic elements inside.
Lets say you are running an electric drill for 5min. The breaker elements are warmed up, but haven't quite tripped yet. If you stop and start the drill again, it can trip the breaker more easily because of the insrush and the breaker elements are already warm.

Google images of "circuit breaker trip curve" to understand the relationship of overcurrent and trip time. It will probably amaze you. (they handle much higher than the rated current)

This is why time delay fuses were invented. (that and an apparent shortage of pennies!) If you're too young search for Edison penny trick. 😉

 

[geecee]

Thanks for the replies everyone. I had quite a few big tree branches down here from the freak snow storm that hit the northeast this past weekend, and was going to borrow a neighbor's electric chainsaw to do some cleanup. I have some outdoor outlets but I have no idea what they are rated for, so I'm assuming that they are standard 15amp outlets, and from what I've seen online at Amazon, some of these chainsaws have up to 15amp motors on them. It's not a big saw, so I'm guessing that its probably less than that, so I'll give it a shot and see what happens.

 

[GuitarDaddy]

Sounds like you have it figured out, just make the connections at the panel last, the hot leg goes into the breaker and the neutral and ground go to bars in the panel on most panels (ck specific instructions for your panel type).

I recommend that you turn off the main breaker and use a battery powered light to make the connections in the panel, but remember to still be careful while working in the panel and always treat every hot wire as if its live just for safety precautions. Connect the three wires, snap the breaker in, then turn main breaker on.

And you should put the outlet box where you need it, no need to locate it near the panel. It's too easy to drop romex in a wall where ever you need it. Just start out with your roll of romex in the attic and locate the top plate of the wall above the spot in the wall where you want the outlet, drill a hole through the top plate into the wall and drop the wire down the wall.

Unless the wall is stuffed with insulation you won't even need the fish tape, if it is full on insulation then run the fish tape down the wall to the outlet hole and pull the wire up from the outlet hole. At the panel there will already be a hole through the top plate so you just need to drop it down and fish it out of the top of the panel.

 

[tm37]

Yes. The breaker or fuse is there to protect the wire in the wall. You have used a toaster, right? The metal strips that glow red inside are heating elements. Similarly, the wires in the wall of your house will also glow red if you pass too much current through them. The breaker is there to prevent that from happening.

Normal outlets in your house are 110v/15-amp. The wire that attaches the outlets to the main fuse box are sized appropriately (typically 14-gauge). The outlet for your stove or electric dryer is different b/c it handles a higher voltage and much more current. The wires that connect those outlets to the breaker panel are much thicker (12 or 10 gauge) and the breaker is sized accordingly .

stoves typically run on 115v. Current and voltage are different. 🙂

Electric dryers will run on 220V ~ 240V

Also Voltage never killed anyone. However Current is a killer 🙂

 

[skyking]

stoves typically run on 115v. Current and voltage are different. 🙂

Electric dryers will run on 220V ~ 240V

Also Voltage never killed anyone. However Current is a killer 🙂

No, every electric stove I have had contact with was 220 as well. You are right about the rest.

 

[Red Squirrel]

Lots of smoke!

http://www.youtube.com/watch?v=T8GiuM-gABY&

Romexsmoke! Don't breathe this! :biggrin:

Wow!

I've always wanted to try this as a curiosity, but wow, did not figure the results would be that drastric. I'm still curious to see what would happen with 20 amps on #14 though. My guess is it would take longer, but still eventually fail. In a way that's more dangerous as one will wire it wrong, turn it on for a bit and see that "it works fine" then go do the groceries with a 20 amp heater still plugged in and turned on.

 

[JEDI]

What about the wiring in the wall? If it's not the appropriate gauge it could cause a fire.

14ga can handle 20amps.
it's just code that says 14ga is 15amp max

 

[futuristicmonkey]

A resistive load of 15A will not trip a 15A breaker, no matter how long it is present.

This is incorrect. Residential type breakers will trip at 100% rated current typically within 1 or 2 hours. There is wording in the code (both of NEC/CEC) which requires different protection/cabling for "continuous" loads. See imagoon's post, above.

 

[futuristicmonkey]

14ga can handle 20amps.
it's just code that says 14ga is 15amp max

That depends on its insulation. Some wires are rated for 75*C, others 90*C, some 150, some 200,.....it all depends on your application.

 

[MichaelD]

Well, I pulled the cover on the breaker box. Much to my surprise all the breakers are 20 amps, including the one for the existing GFCI outlet in the garage.

I am not sure if the wiring is 12ga though. I don't think it is.

I don't want to assume, but: If this house is only 5 years old AND all the breakers are 20 amps, is it probable that the wiring is 12ga in order to handle 20 amps? BUT the outlets are NOT 20-amp receptacles. They do not have one slot horizontal like a 20 amp outlet does. What is the deal with this? :\

 

[Red Squirrel]

That *looks* like 12 awg, but I'd try to get a reading on a wire to make sure or compare it with a known size. I would hope that whoever wired it did it to code.

Only thing, is there any lighting circuits on there? I thought it was not legal to put lighting on a 20 amp circuit, as most light fixtures are only rated for 15 amps.

 

[MichaelD]

Every light and outlet in the house are on that panel except for the AC, Dryer and Water heater. They are on a separate panel outside the house, right above the meter. How do I see if the wire is 12ga? I have a digital micrometer...but that wouldn't really work...wire thickness (with the jacket) doesn't mean anything.

 

[Red Squirrel]

I would find a piece of 14 (the actual wire (without jacket) and just compare the copper ends. Though there are actual tools to check, but not something everyone has lying around.

 

[Modelworks]

CLIFFS

I want to add a 20-amp circuit/outlets in my garage b/c there's only one existing 15-amp GFCI outlet in the garage (which is gang-wired with a few other outlets inside the house), and the associated breaker trips when I try to run the table saw and dust collector.

That is normal for GFCI outlets and usually not because of the load but because of the noise induced from the motors causing the GFCI to trip.

Not looking for fancy. I want a simple, surface mount outlet box with the standard shiny metal conduit running from it to the breaker box. Said breaker box is also located in the garage, about 20 feet from where I want the outlet.

Code states outlets must not be more than 6 feet from one outlet to the next , in a non living space like a garage the code doesn't apply UNLESS you make it a living space which using it for a home workshop does. The idea is that whatever your intended usage for the space you shouldn't be more than 6ft from an outlet for whatever you have to power.

I contacted a local licensed/bonded electric contractor and they quoted me $500 for the job. This is a new house (6 years old), BTW. This job requires about $60 in supplies; everyone knows this.

True it will cost more to hire someone, but you are paying for the peace of mind that it is done right and your home will not burn down.

I have changed outlets, installed dimmers, ceiling fans etc before, safely (appropriate gauge wire, grounding etc) but never done something like this before.

Would someone please tell me how to wire a 20-amp breaker into the box and run the wire?

The very first thing you want to do when you start to work is turn off the main service disconnect. This will be the largest breaker in the box and will usually be rated 200 amps. Do not ever open a breaker box without turning off the service disconnect first. That will turn off both phases of the power on both sides of the breaker box. Be careful though because the rails near the very top where the disconnect breaker is located can still be HOT and if you contact them there is NO DISCONNECT OR SAFETY DEVICE between you and about 4000 amps of current. Most boxes will have those covered by a guard of some sort but not all. Depending on the install you can have one where the power goes from street to meter to breaker box with disconnect or you could have one where it goes street to meter to disconnect in its own box then breaker box. Whichever you have make sure to turn off the disconnect closest to the meter .

After you remove the cover use a meter to verify that the power is off, don't trust the breaker.

The best way to wire something like a garage is with metal clad and metal boxes. I would do a couple outlets and string the metal clad between each of the boxes making sure to secure the metallic casing of the cable to each box so the ground is on the cable shield and the metal boxes. Using plain romex cable in a garage is against code because it can be snagged or cut by normal day to day task in the garage. I would go with AWG 12 wire due to the load that things like saws have when they first start.

Height requirements for code have changed, outlets are to be 4ft. 6 inches from the floor for a standard outlet and anything below that height has to be child proof. Breakers are recommended to be AFCI type for all new breakers installed, they detect when two wires touch and kill the power. Garages can also be wet locations so that adds the GFCI requirement as well so you would need a ARC Fault + GFCI combination breaker.

 

[Modelworks]

I don't want to assume, but: If this house is only 5 years old AND all the breakers are 20 amps, is it probable that the wiring is 12ga in order to handle 20 amps? BUT the outlets are NOT 20-amp receptacles. They do not have one slot horizontal like a 20 amp outlet does. What is the deal with this? :\

You will not find 20A outlets in most homes. The breakers are sized for the total outlet load not for each outlet as a single load. 12AWG is used for 20A but some will also use 10AWG depending on the length of the run. Some newer homes have moved to the new code allowing 30A breakers even though the outlets never exceed 15A.

 

[edro]

That looks like 12g to me and the box looks professionally done and since all breakers are 20A, it is 99% likely it is 12g.
The installer didn't have to use 20A receptacles just because he used 20A breakers.
15A receptacles are cheaper than 20A. It is common to find 15A receptacles on 20A circuits.

 

[Rubycon]

That depends on its insulation. Some wires are rated for 75*C, others 90*C, some 150, some 200,.....it all depends on your application.

Yes pulling 20A on 14AWG increases voltage drop and conductor temperature. Aluminum conductors (no longer used on small branch circuits - typically used on larger 240V loads and main feeds) will also have lower ampacity and higher voltage drop per same distance.

A 14AWG wire 100 feet from the panel will definitely have excessive voltage drop if a 20A load is presented.

 

[imagoon]

You will not find 20A outlets in most homes. The breakers are sized for the total outlet load not for each outlet as a single load. 12AWG is used for 20A but some will also use 10AWG depending on the length of the run. Some newer homes have moved to the new code allowing 30A breakers even though the outlets never exceed 15A.

Sounds a bit strange to me here, running 30A through a 15A outlet. I need to check my NECA book on that. Typically the rule is that all devices in the circuit have to support the full load of the breaker. IE a 30A breaker = 30amp switch, 30amp outlets etc because there is the potential that a 15amp switch loading at say 24amps could well... catch on fire and not pop the breaker.

 

[Shawn]

don't do anything in this vid: http://www.youtube.com/watch?NR=1&v=GGeOjASps7w

 

[skyking]

20 amp breaker and multiple 15 amp outlets is common.