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Old 02-17-2010, 06:40 PM   #1
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Checking a Breaker


Having bought a hybrid table saw wired for 110 but easily convertible to 220, I first decided to take a look at the extension cord I am using as well as the existing circuit. Now I am wondering if the breaker controlling the circuit is faulty.

Perhaps I should say that I am located in Southern California and the house is 20 years old.

The circuit is controlled by a 15 Amp breaker. It is not a duplex. The lights in the garage run off a separate circuit.

I can't tell gauge of the extension cord without destroying the cord, which is thicker than the cheapies and about 25" long. The plugs are stamped 5-15. I assume that means the wiring is not 12 gauge (why use a 15 amp plug with 20 amp wire)and guess it must be 14. I can't imagine it being as light as 16, given what it will power.

This is the deal. I can run my rigid 4511 ts (13 amp rating) and the 4.5 hp shop vac, but when I turn on the 12" DeWalt Miter Saw (15 amp) the breaker on the cheap "Prime" brand (Lowes) power strip opens. The same is true if I leave the table saw off and run the old 2-1/2 HP Craftsman Bench Type Table Saw (13 amp). I realize that nothing is at full load as no work is being done and I suspect it is the start up surge of the miter saw that is popping the power strip breaker. This is probably a good thing as the load I am putting well exceeds its 15 amp rating.

I then attempted to see if the panel breaker would trip if some of those amps were routed around the power strip. So I disconnected the miter saw from the strip and plugged it into the same wall outlet via a 75' unknown gauge cord. The table saws and shop vac were left running. Though I turned the miter saw on and off several times, nothing opened and I detected nothing.

Then I did the same, but with the lights and fans for the service porch and powder room running, all of which are on the same circuit. Nothing, even when I cut a 4X4 fence post on the miter saw at a 45 degree miter.

My concern is why isn't the panel breaker opening and how to I check it out.

Also, it now seems that the power strip breaker opens with less of a draw upon it, which doesn't bother may as it cost a few bucks and I would rather it was more sensitive than not. I should probably invest in a decent power strip, if anyone can suggest one.

Thanks for your suggestions.

A sticker on the outlet cover says GFCI. I believe the brand of the breaker is I-T-E and it may be a replacement for the original that was probably a Challenger. (I think I got it at HD).

Thanks.


Last edited by Klawman; 02-17-2010 at 07:31 PM.
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Old 02-17-2010, 08:42 PM   #2
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Checking a Breaker


You can only run one of those devices at a time on a 15 amp circuit. There is nothing wrong with your breaker you are overloading it.
And the shop vac can't be 4.5 HP it would need a 40 amp circuit. It's one of those fake peak HP ratings.

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Old 02-17-2010, 10:26 PM   #3
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You can only run one of those devices at a time on a 15 amp circuit. There is nothing wrong with your breaker you are overloading it.
And the shop vac can't be 4.5 HP it would need a 40 amp circuit. It's one of those fake peak HP ratings.
The point of intentionally overloading the circuit was to test the breaker, but it never opened even when I routed the miter saw around the power strip's own breaker.

I would add that a young guy at the local HD, who is in his fourth year as an "electrician's apprentice", told me to replace the 15 amp breaker with a 30. He also said that the circuit was fine as long as it wasn't starting a fire. Sad.
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Old 02-17-2010, 10:47 PM   #4
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The breakers used in power strips are incredibly cheap, and will trip with any kind of overload.

A panel type circuit breaker has two trip units in it. Short-term and long term.

The short term will trip instantly when the current exceeds about 12-15 times the rating of the breaker. This is to allow for motor starting surges, which are usually about 6-10 times the amp rating of the motor.

The long term will hold the rating of the breaker forever, trip at about 10 seconds at twice the rating, and about 3 seconds at 3 times the rating. This is to protect the wire connected to the breaker.

A power strip breaker usually has only one trip unit, the short-term. They usually won't start much of a motor, where a panel breaker will.

Rob
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Old 02-18-2010, 12:28 AM   #5
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Checking a Breaker


Thanks, Micromind. Now I see why Joed may have said there was nothing wrong with my breaker, as the circuit wasn't subjected to overloads for that long, due to the power strip popping so quickly.
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Old 02-18-2010, 08:55 AM   #6
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The point of intentionally overloading the circuit was to test the breaker, but it never opened even when I routed the miter saw around the power strip's own breaker.
I misinterpretted your post. I thought you were having issues with the breaker tripping. It could be that the devices are not drawing the current if they are not loaded or the breaker could be defective. If you are in doubt replace it. Plugg in some heaters if you really want to test it. You know the watts being used for sure.
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Old 02-18-2010, 01:31 PM   #7
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Checking a Breaker


Joed. Your idea space heater idea is a good one, but as I am in So Cal I have none, but I will try a coffee maker, an iron, and electric toaster/oven. I will remove the power strip to take it out of the mix. Based on their wattage, they should have respective draws of about 8 1/2, 8, and 12 amps when set so that they are using maximum power (as when the appliance is first turned on.) Thank you. Your confusion was no doubt my fault. How did you like the suggestion by the "electrician apprentice" at the Home Depot; replace the 15 amp breaker protecting a 15 amp line with a 30 amp breaker?
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Old 02-18-2010, 02:18 PM   #8
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That guy at HD should be fired for giving that type of advice.
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Old 02-18-2010, 02:29 PM   #9
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The guy at hd should give up his apprenticeship , if he hasnt figured that much out in 4 years.
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Old 02-18-2010, 05:42 PM   #10
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Journeymanj and Joed: I always think at least thrice before doing anything that might cost someone their job, but that guy at HD was an idiot. As politely as I could, I told him that was the worse advice I had ever heard and it was like replacing a fuse that keeps blowing with a penny. The idiot even said there was no problem as long as there was no fire and I told him that burning down my house was not what I called a good way to discover faulty wiring. When I told him this I think he realized that he had screwed the pooch real bad and he offered to call a licensed electrician friend. He called him and the guy said to replace the breaker with another 15 if I suspected it was bad or test it with a coffee pot. Someone here, I think Joed suggested a portable electric heater.

I just ran a test and am no longer concerned that the breaker may not be working (which is not the same as my concern over the fact that 14 gauge and 12 were both used on the same circuit, which I suspect is why it has a 15 and not a 20 breaker. That is covered by another thread to which I have received good responses, though they mean more work.)

Anyway, I took the power strip off of the end of what I believe is a 14 gauge extension cord and hooked it up to a coffee pot, a toaster oven, and a 10 inch saw. I estimate even without the saw being under a load, the three were drawing around 20 amps. After about 7 seconds I turned on the miter saw and the breaker still didn't pop, but a few seconds after I began cutting into a 4x it opened. I then reset the breaker and restarted all but the miter saw. The breaker opened after about 30 seconds.

Thank you all for your help
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Old 02-18-2010, 07:22 PM   #11
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That sounds about right for that breaker. You've proved that the long term trip unit works, and given that, the short term almost certainly works as well.

Rob
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Old 02-18-2010, 07:48 PM   #12
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That sounds about right for that breaker. You've proved that the long term trip unit works, and given that, the short term almost certainly works as well.

Rob
Thanks for the tips. I am satisfied that it's a good breaker. My concern was never with replacing a $5 breaker, but if it was bad I would have to consider the cause.

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