am I overloading my 15 amp breaker

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redm18

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I have a 15 amp breaker that powers the outlets electical in my garage which has a freezer for food 5 amps a mini fridge 1.2 amps the .5 HP garage door opener and 3 40 watt bulbs would adding a second 5 amp freezer (keezer) to this breaker overload it to much? I could and probably will get rid of the mini fridge and I could go to led light bulbs if I need to but I'm just wondering if I would be risking burning my house down in the short term
 
You won't burn your house down, you will trip the breaker. Plug it in and see. The worst that will happen is all your food in the freezer thaws out and you pour a warm beer.

Unless the freezers start at the exact same moment, you should be fine though.
 
Doing some quick math in my head and it looks like adding the second freezer will throw you over the top. You only want to go to a max of 80% which would be 12 amps on a 15 amp circuit. The breaker is supposed to trip on an overload, but do you really want to rely on that? If it doesn't trip and continues to overheat, suddenly you have yourself a house fire. Not worth the risk in my book.
 
one thing you have to be aware of is that the running amperage of a device is nothing compared to the starter current required. fwiw it is 600% of the running current.

its the same thing when you turn your vacuum on and the lights dim for a second...
 
I wish people would stop spreading the lie about the 80% rule on this forum, or at least use it appropriately. If you have a 15 amp breaker on a branch, you can use 15 AMPS CONTINUOUS, 24/7/365.25. 14 ga wire is rated for 20 amps minimum in residential settings per the NEC. But, the NEC also requires overload protection of 15 amps for 14 ga wiring. If you do the math, 15/20 = 75%. YOU WILL NOT EXCEED 80% CAPACITY IN YOUR HOME! I hate to yell like that, but internet electricians have been pushing this false fact for as long as I have been coming to this forum.

Source:
http://ecatalog.squared.com/pubs/Ci...eakers/QO-QOB Circuit Breakers/0600DB0103.pdf

Now, I am a mechanical engineer, not an electrical one, but I know enough to know how to read and I have taken my share of EE courses. I do encourage someone to disprove me though if I am off base here.

As for wire ratings, I run 25 amps continuous through 14 ga conductors in my control panel. That 15/20 amp rating is only for bundled conductors. The rating is higher for single conductors in open air like in chassis applications. It all comes down to temperature rise and the NEC rules for residential applications are VERY conservative just because you never know.

Source - pg 184
http://std-wire.com/downloads/SWC_Catalog.pdf
 
You can if you have 12 ga wire. You MUST use a 15 amp breaker on a 14 ga branch to keep the NEC and electrical inspector happy.
 
Fwiw, I have 3 freezers(running happily) on the same 20 amp circuit in my garage.
 
I wish people would stop spreading the lie about the 80% rule on this forum, or at least use it appropriately. If you have a 15 amp breaker on a branch, you can use 15 AMPS CONTINUOUS, 24/7/365.25. 14 ga wire is rated for 20 amps minimum in residential settings per the NEC. But, the NEC also requires overload protection of 15 amps for 14 ga wiring. If you do the math, 15/20 = 75%. YOU WILL NOT EXCEED 80% CAPACITY IN YOUR HOME! I hate to yell like that, but internet electricians have been pushing this false fact for as long as I have been coming to this forum.

Now, I am a mechanical engineer, not an electrical one, but I know enough to know how to read and I have taken my share of EE courses. I do encourage someone to disprove me though if I am off base here.
The 80% rule, IS NOT a ratio of breaker sizing to wire sizing.

Actually the codebook says the breaker 'shall not be less than the noncontinuous load plus 125 percent of the continuous load.' Sec NEC 215.3

When you size a breaker for 125% of the continuous load, then you are at 80% capacity. What this means is you can run a noncontinuous load at the full rating of the breaker, but a continuous load will generate heat and eventually cause the breaker to trip. There are 100% rated breakers available, although you probably have to special order them.

Now, the freezer may not be considered a continuous load with it cycling on and off. But I'm no internet electrician. :cross: I'm also a mechanical engineer, but I work for a switchgear manufacturer.
 
So it comes down to breaker sizing and not conductor sizing. I hate to admit that I am ever wrong, but I stand at least partially corrected. I still do not hesitate to run breakers at capacity, but then again my applications rarely require more than 10-30 minutes of continuous load.

And, I'm sure that our public school system educates people on the "80%" rule of thumb so they never plug a 1,500 Watt heater into an outlet that is on the same branch as their 50" TV and floor lamps because that would surely burn down a house. :rolleyes: Sorry, I had to.

ETA: I'm highly skeptacle that in 90% of applications of multi conductor Romex installation that you are ever going to generate enough heat at NEC ampacity guidlines to impact the integrity of the wire. If breakers trip from internal heating, that is another issue.
 
Sorry to keep beating this horse, but I think that I've satisfied my curiosity and can put this to rest. I'm assuming that residential breakers are not rated at 100% but I can brew an entire batch of beer in under 3 hours so I'll pull 30 amps all I want and not worry about it.

NEC 210.19, 210.20, 215.2, 215.3 and 230.42 permit conductors and overcurrent protection to be rated for 100 percent rather than 125 percent of continuous current “where the assembly, including the overcurrent devices protecting the [circuit] is listed for operation at 100 percent of its rating.” An important factor is that the assembly, meaning the switchboard, panelboard or similar equipment, is listed for operation at 100 percent of its rating as well as the OCPD. The additional current flowing will cause additional heat. If the assembly has not been listed for this application, temperatures may easily become excessive for the conductors and insulation.

http://www.iaei.org/magazine/2002/03/overcurrent-protection-and-the-nec/
 
I wish people would stop spreading the lie about the 80% rule on this forum, or at least use it appropriately. If you have a 15 amp breaker on a branch, you can use 15 AMPS CONTINUOUS, 24/7/365.25. 14 ga wire is rated for 20 amps minimum in residential settings per the NEC. But, the NEC also requires overload protection of 15 amps for 14 ga wiring. If you do the math, 15/20 = 75%. YOU WILL NOT EXCEED 80% CAPACITY IN YOUR HOME! I hate to yell like that, but internet electricians have been pushing this false fact for as long as I have been coming to this forum.

Source:
http://ecatalog.squared.com/pubs/Ci...eakers/QO-QOB Circuit Breakers/0600DB0103.pdf


Now, I am a mechanical engineer, not an electrical one, but I know enough to know how to read and I have taken my share of EE courses. I do encourage someone to disprove me though if I am off base here.

As for wire ratings, I run 25 amps continuous through 14 ga conductors in my control panel. That 15/20 amp rating is only for bundled conductors. The rating is higher for single conductors in open air like in chassis applications. It all comes down to temperature rise and the NEC rules for residential applications are VERY conservative just because you never know.

Source - pg 184
http://std-wire.com/downloads/SWC_Catalog.pdf


I am an Electrical Engineer and I have to say the NEC differs with you greatly here. For circuits under a continuous load you should not size the circuit for more than 80% of the breaker size. I have designed equipment for the charging of electric cars that run at 32 amps and guess what they require a 40A breaker per the NEC. It is always better to be safe than sorry and follow building codes
 
Sorry to keep beating this horse, but I think that I've satisfied my curiosity and can put this to rest. I'm assuming that residential breakers are not rated at 100% but I can brew an entire batch of beer in under 3 hours so I'll pull 30 amps all I want and not worry about it.
Scientifically, theoretically and by code, you can pull 30 amps for 2 hours and 59 minutes on a 30A breaker, but I've seen enough burned up switchboards that I wouldn't intentionally run it at it's maximum. The breakers do have thermal trips in order to drop the load when it starts to overheat, but what would happen if the breaker failed to trip?
 
So based on the spirited debate here I could probably run everything on the circuit but as I am sitting somewhere around 15 amps if every single load is running at the same time its not the best idea in the world but likely won't burn my house down. I think I will probably just hook everything accept the mini fridge. My neighbor is an electrician and he has offered to help me install an additonal circut out to the garage so I will have him do that when he gets the time. Does this plan seem reasonable?
 
The thing that will get you in trouble redm18 is the inrush or start-up current of the devices. Most appliances will have two current draw ratings, the starting current and the operating current; with the start-up being considerably higher than the operating for motors and other induction loads. Having extra capacity in the garage is never a bad investment; I wish that I had more than 20 amps available in mine.
 
The thing that will get you in trouble redm18 is the inrush or start-up current of the devices. Most appliances will have two current draw ratings, the starting current and the operating current; with the start-up being considerably higher than the operating for motors and other induction loads. Having extra capacity in the garage is never a bad investment; I wish that I had more than 20 amps available in mine.

Yes, but everything would have to start at the exacxt same time to overload it. That's a slim chance. Like I said, 3 freezers on one circuit, no problems.
 
The breaker is sized to protect the wire in the wall. I would recommend getting a second circuit from the elec nbr. ask him about up sizing the breaker. Or you could get a kill-a-watt and measure the actual amps used by each device.
 
My keezer has a "start-up" rating of 12A and a "operating" rating of 1.69A.

Does that means it draws 12 A during initial startup? How long does it draw this current for?

Assuming these number are accurate, do I need to assume that 2 of these freezers will trip my 20A circuit breaker if they trigger simultaneously?

Also, is my only worry that I will trip the breaker? (i.e. how high of a current draw do you need to get to before you need to worry about causing a problem that the breaker cannot prevent).

Very ignorant on electricity and would appreciate any insight that can help clear this up for me.
 
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