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15 vs. 20 amp circuit upgrade

#1
03-19-19, 08:00 AM
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15 vs. 20 amp circuit upgrade

I'm wondering if I can swap out a 15 amp breaker and replace it with a 20 amp breaker. I know this has to be a serious no, no, but I have a gadget that draws 19 amps.

In my 25 y/o house electrical panel I have a variety of 15 and 20 amp breakers (plus some other, higher amp/volt circuits). In my garage I have a specific need for 20 amps, but the outlet there is on a 15 amp circuit.

I'm just wondering, did the electrician who wired the house use the same cabling for the 15 & 20 amp circuits and just put in a 15 amp breaker b/c that's what he had on hand that day? Or, did he use a smaller gauge wire?

I'm looking for thoughts about switching the breaker, and what I can do to safely test the upgraded circuit. Also, how can I determine the gauge of the existing wire?

F

Last edited by garberfc; 03-19-19 at 08:21 AM.
#2
03-19-19, 08:12 AM
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The wire has to be at least #12 to support a 20A breaker. If 15A the wire is most likely #14.
What is the device that draws 19A? Technically that's too much draw from a single device on a 20A circuit.

#3
03-19-19, 08:20 AM
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It's the Air Force Master Blaster dryer.

How can I tell what gauge the wire is? I can measure the diameter with a micrometer, but I don't know what to look for....

#4
03-19-19, 08:29 AM
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I found a site the lists the gauges of wires. I also measured the diameter of the wire and it's .0065 inches making it 14 gauge, also, it's a single copper wire. If I'm reading the charts right makes the max amperage 15. That also means that I'm SOL

#5
03-19-19, 08:38 AM
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If you can see the jacket somewhere it should be stamped with the size. Assuming it's Romex. If in conduit the individual wire should be stamped.

#6
03-19-19, 08:57 AM
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So, it looks like I need to run an additional circuit to the garage. Knowing that I'll be pulling 19amps, should I run 10 gauge wire? Does GE make 30amp single pole breakers? Do I need a special outlet, or are they all capable of handling the higher amperage?

Thanks for the help!

#7
03-19-19, 09:37 AM
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That unit should be on a 30 amp circuit with #10 cable.

#8
03-19-19, 12:58 PM
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You have not said what it is that draws 19A. Is it a plugin appliance or should it be hardwired?

#9
03-19-19, 01:09 PM
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There was a link down in posting #3, but here it is again: https://www.metrovacworld.com/produc...aster/overview

I'm going to run a new circuit and place a double box in the garage. The outlets will be standard duplex 20 amp as I don't see any rated for 30 amp...

#10
03-19-19, 01:18 PM
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Sorry, I missed the link. Even though it shows 19A the US pictured plug is a standard 15A. 20A circuit should be okay if that's the plug that comes on the air blaster.

#11
03-19-19, 01:24 PM
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It seems that the actual problem here is that the device is made a small manufacturer and it does not appear to be listed by any NRTL such as Underwriters Labs for electrical safety or compliance.

There is also conflicting information. One of the specs state 19A; one states 18A, however the picture shows a 5-15 (15A) plug and cord on the device. They also state 8 HP peak (HA!) and states 2,100 watts power consumption. None of these are consistent.

All of this leads me to believe the manufacturer is "winging it" on the electrical design, and we don't really know what is true.

#12
03-19-19, 02:45 PM
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Hi, here is an explanation I found about Peak HP.
I will try to keep this as basic as possible. Horsepower is defined as 746 watts of power. Assuming a motor is 75% efficient (which is actually on the high side!), the motor will consume 1000 watts for every horsepower that goes out the motor shaft. The difference between 1000 and 746 (254 watts) is lost in the form of heat. That is why all electric motors get hot. To get 1000 watts with 120 volt AC power, takes 8.3 amps (1000 divided by 120). So for every one horsepower, it takes about 8.3 amps of power at 120 volts. Therefore a 4hp dryer would use 4 x 8.3 = 33.3 amps and an 8 hp dryer would use 8 x 8.3 = 66.4 amps.

Yet they list their 4 Peak HP dryer at 9.5 amps and their 8 Peak HP dryer at 19 amps. How can this be?
Geo

#13
03-19-19, 03:01 PM
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peak HP has always been a lie; esp. with home vacuum cleaners and boat trolling motors.

As Ben noted, the specs are flaky. The cord is "heavy duty".

#14
03-19-19, 03:32 PM
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Thanks folks for all the awesome information. I'm going to err on the save side and run a dedicated 30A circuit using 10/2 romex . The week point of the setup is the 20A outlet. That'll be in a metal box.

Thanks again,
F

#15
03-19-19, 03:34 PM
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Have you measured the amperes drawn using a Kill A Watt unit or a clamp on ammeter?

A device with a "standard" 120 volt plug that is used for a few minutes or maybe an hour at a time such as a vacuum cleaner or cake (or concrete) mixer should not draw more than 15 amps after it starts up and gets going.

A "standard" 120 volt duplex household receptacle or even a 20 amp receptacle may be installed on a branch ci rcuit of at most 20 amps regardless of how many receptacles there are.

#16
03-19-19, 03:40 PM
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I haven't purchased the gadget yet. I was just planning ahead. I'll check the wattage / amperage once I get it.

Why is it that extension cords that are 10/3 rated at only 15 amps??

Can anyone recommend a good quality extension cord maker? Preferably made in the USA?

Last edited by garberfc; 03-19-19 at 04:11 PM.
#17
03-19-19, 04:39 PM
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According to the instruction sheet https://www.metrovacworld.com/download/file/fid/1051 that unit comes with a 15 amp plug. Since it is not a continuous load I would install a dedicated 20 amp circuit and a 15 or 20 amp receptacle. If the receptacle will be in a garage it will need GFCI protection.

If you need a cord I would recommend a 12/3 cord.

#18
03-19-19, 05:07 PM
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Why is it that extension cords that are 10/3 rated at only 15 amps??
Probably because it has a 15A plug on it. Still useful for long runs in the back yard, however. The heavy gauge reduces voltage drop.

#19
03-19-19, 05:53 PM
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You can't put a 20 amp receptacle on a 30 amp circuit. You must use a 30 amp receptacle. By code the receptacle has to match the circuit.

#20
03-19-19, 06:27 PM
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By code the receptacle has to match the circuit.
Then why can you have a 15 amp receptacle (duplex) on 20 amp circuit? (He asks knowingly )

#21
03-19-19, 07:12 PM
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You can't in Canada. But that is the one exception in the USA IF you have more than one outlet. A single outlet must match. A duplex receptacle counts as two outlets.

#22
03-20-19, 03:47 PM
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The OP is not in Canada, they are in CT USA. I do recall that code being different between NEC and CEC.