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I have a new -80 deep freezer that calls for NEMA 6-15R receptacle, but the old one it is replacing called for a NEMA 6-20. I note that the plug actually seems to fit in the 6-20, but is there a reason that this would cause a problem? The machine should only draw the lower amperage, so the fact that the outlet is overrated wouldn't be a problem?

Maybe I'm missing something.

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5 Answers 5

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Ideally, a fuse or breaker should not be rated higher than the weakest link in a system.

If a piece of equipment is rated below the fuse or breaker rating, it becomes a sacrificial device in the event where it draws more than its current rating but less than the fuse or breaker rating.

A device rated for a NEMA 6-15R receptacle that is connected to a NEMA 6-20R receptacle will be allowed to operate within its design parameters, but will also be allowed to draw current above its design parameters.

Edit: Many devices have built in protection allowing them to be connected to a variety of sources. The notes above pertain primarily to pieces of equipment that do not have built in protection and rely on the source protection.

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So I shouldn't plug my 0.5A lamp into a circuit protected by a 15A breaker? I should instead plug my five 0.5A lamps, into a single circuit protected by a 0.5A breaker? –  Tester101 Jun 25 '13 at 17:58

tl;dr

15 Ampere cord-and-plug appliances can indeed, safely be connected to 20 Ampere receptacles.

A deeper understanding

NEMA 6 is a design standard for three wire grounded cord-and-plug devices and receptacles. The number after the dash (-), is the current rating of the device. For example. A NEMA 6-20 device, would be a three wire grounded cord-and-plug device capable of withstanding 20 amperes of current. The "R" simply tells you that the device in question is a receptacle. A NEMA 6-20 cord-and-plug device, would plug into a NEMA 6-20R device.

The NEMA design standard is a safe and convenient way to determine what can connect to what. Basically, if it fits, it works.

If a 15 Ampere device is connected to a 20 Ampere rated receptacle, the device will still only draw a maximum of 15 Amperes. Plugging the device into a higher rated receptacle, will not cause it to draw more current.

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Good to know. I'm talking to the manufacturer rep now, and they are implying that it should only be plugged into 6-15, not a 6-20 (I specifically asked). I'm trying to be escalated up the support to see if they can give me a reason, but it seems like it should be fine. (Can't accept your answer yet due to time). –  Atl LED Jun 24 '13 at 17:40
    
Thanks for the deeper understanding. That was my impression, and I feel like I'm being fed something from the manufacturer where there is an answer in a customer service book, not someone who understands the electronics. –  Atl LED Jun 24 '13 at 17:52

The fact that your NEMA 6-15 plug physically fits in a NEMA 6-20R receptacle tells me it is a supported configuration.

Note how a NEMA 6-20 plug will not physically fit in a NEMA 6-15R receptacle.

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The outlet is not the fuse or the breaker, so as long as everything is rated it'll be fine. Going larger on wiring or outlets is only insurance, it cannot hurt a thing. The breaker or fuse is what is limiting the circuit's capacity as is desired. You would never want the wiring to be the weakest link. It is the same with doing a job to code, code is the minimum standard.

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From my understanding, then it would be wise to use a 15A breaker on this circuit. I'm assuming this is a dedicated circuit too.

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There's no problem plugging in a device that draws less current than the circuit is rated for, in fact you do it all the time. –  Tester101 Jul 23 at 11:00

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