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Old 09-21-2008, 03:26 PM   #1
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an easy way to deterimine if old plug is 20 or 30A?


Hello there!

i have a dorky question, i am sure. i have an old outlet in my spare bedroom that looks like a round 220V outlet - it's right below a window so i am assuming it's from an old window A/C unit (the house had central H/A when i bought it).

is there a way for me to determine how many amps this outlet allows? i have a 240V 28A plug i need to use.

my breaker box is a mess - nothing labeled, and i don't have anything to test whether or not the outlet is on or off if i go through and turn stuff off.

thanks for any advice

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Old 09-21-2008, 03:36 PM   #2
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an easy way to deterimine if old plug is 20 or 30A?


You need to turn off power and pull the recep out to check the wire size.

#14 is good for 15A, #12 for 20A, and #10 for 30.

It's probably 14 or 12 (15 or 20 amps)

The breaker will be a 2 pole breaker. Turn your 2 pole breakers off one at a time and test power.

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Old 09-21-2008, 05:01 PM   #3
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an easy way to deterimine if old plug is 20 or 30A?


perfect, thanks
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Old 09-21-2008, 07:56 PM   #4
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an easy way to deterimine if old plug is 20 or 30A?


Take the cover plate off and look at what's stamped on the yoke. It should state it's voltage and amperage rating.
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Old 09-21-2008, 09:01 PM   #5
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an easy way to deterimine if old plug is 20 or 30A?


Go here and identify the receptacle. Each shape has its own voltage and current rating.

http://www.powercabling.com/nema.htm
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Old 09-21-2008, 10:49 PM   #6
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an easy way to deterimine if old plug is 20 or 30A?


Quote:
Originally Posted by joed View Post
Go here and identify the receptacle. Each shape has its own voltage and current rating.

http://www.powercabling.com/nema.htm
The problem with that chart is both the NEMA 6-15 and 6-30 look the same.

While the configuration appears to be the same, the difference between them in reality is quite huge.

The 15 Amp one is 1.31" in diameter, while the 30 Amp one is 2.11" in diameter.

In simple terms, the 30 Amp one is the same physical size as your standard dryer receptacle.

So, is the receptacle a large one like a dryer, or a smaller one, similar to any standard receptacle?

The other thing to consider is some of the older A/C outlets used the non-grounding crow's foot configuration (NEMA10-20). Those should be replaced in any case.
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Old 09-22-2008, 08:51 AM   #7
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an easy way to deterimine if old plug is 20 or 30A?


here is a better diagram. The differences are easier to see. Also the votlage and current is probably written on the receptacle somewhere if get down close and look.

http://nooutage.com/nema_configurati...Configurations
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Old 09-22-2008, 08:58 AM   #8
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an easy way to deterimine if old plug is 20 or 30A?


whelp - after looking at it, it's small (not larger like a dryer outlet) with 2 horizontals and the grounding plug..

I do believe it's a 250V, 15A...i will check to see if there is anything written on it when i get home from work.

well, crumb! but it's what i suspected..

thanks everyone for posting!

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