30amp plug to 20amp device

[Michael Wilson]

I want to run a 20amp treadmill on a 30amp outlet. Can I just use an adapter like this and get on with it?

Thanks, friends.

[Michael Wilson]

Thanks, Ralph!

The treadmill tag states:

INPUT 120Voc/60Hz CURRENT 17 A

Sounds like I'm in business.

[Peter]

You didn't say if your 30 amp outlet is providing 120v or 220/240v but most likely, it's 220/240v. I find the description on the web site in your link ambiguous. It's described as an "adapter", not a splitter. I use adapters when I travel abroad so I can use my dual voltage chargers and shaver (with North American 120v plugs) in another country's

220/240v socket. Those adapters don't change the voltage, just match a bunch of round holes to the flat blades on my plugs. Are you sure that the adapter you cite doesn't connect the two hot sides of the 220 outlet to the two flat blade sockets on the female side of the adapter and the neutral from the 220 outlet to the round hole on the female side of the adapter?

Chances are that your assumption is correct. But I would plug the adapter into the 30 amp socket and check the voltage across the adapter's two female slots before connecting or turning on something as expensive as a treadmill just to make sure your assumption (that only one side of the 220 source is going to the adapter's female side) is correct.

[Ralph Mowery]

Yes, if nothing else, just plug in a standard lamp with a 120 volt bulb in it. One of the older filament ones. If the bulb burns very bright and does pops out in less than a minute it is probably a 240 volt output, but I doubt it.

[Michael Wilson]

Thanks for all your help with this! The outlet states: 125/250 V. NEMA 10/30.

[Peter]

I'm not questioning the safety rating of the outlet. I'm questioning whether that outlet is supplying 120 or 220/240 volts. And you can't tell just by examining what it is rated for.

The reason that type of outlet is rated for 250v is that it is commonly used to supply power for electric dryers, ovens, ranges, and other high wattage appliances that are engineered to use the 220/240 supply voltage (yes, including use in countries that use 120v for almost all other electrical equipment).

[trader_4]

There is nothing ambiguous about the description. It clearly describes it as a 120 volt 15/20A adapter, that's what the receptacle shown is. There is no 240V anything that looks like that, for obvious reasons. And nothing mysterious there, it's a 4 wire plug on the other side, so using 3 of those connections it can supply 120V. It's specifically for what the OP wants, using a 240V 4 wire receptacle to be able to plug in a 120V load.

[Dean Hoffman]

One of the pictures shows the male end marked as 125/250 volt with four prongs. The female end is marked as 125 volt with three openings. The connector loses one hot leg in the transition.

[gfretwell]

That is why NEMA standardizes these plugs.

[Ralph Mowery]

Yes, there are NEMA standards.

With all the stuff coming into the US from China and sometimes other countries you never know what they may send into the US.

Where I worked we had some big temperature controlled heaters. They ran on 480 volts 3 phase and anywhere from 10 to 200 amps. There was a big building project and another bank of heates were installed. While setting they up we could not get the high end to reach anywhere the 480 volts. Come to find out the equipment was sent in as 380 volt devices. I don't know what country uses that.

On another note everything that had the 480 volt disconnects green ment that the breaker was supplying power and red ment it was not. Then the European stuff came in and their idea was red ment the breaker was on and it was dangerous to go in the box and green ment the breaker was off and it was safe. Exectally backwards.

I don't remember the colors now,but even the 120 volt replacement cords had blue and brown wires instead of the more normal black and white we use in the US.

[gfretwell]

Ordering low bid stuff from offshore is always a crap shoot but you should verify the voltage ratings are right. I agree Europe uses different marking standards and it is not even standard across the EU. They are trying but old habits are hard to break and it takes a long time to replace all of the installed equipment. The NEC does recognize the European cord color standards tho.

400.21 (C) <Neutral identification> ... For jacketed cords furnished with appliances, one conductor having its insulation colored light blue, with the other conductors having their insulation of a readily distinguishable color other than white or gray.

[trader_4]

It's $20 for a simple adapter and Home Depot is selling it.

I agree Europe uses

[gfretwell]

You are not buying a "simple adapter" from Home Depot to get from 380v to 480 rating.

380v is the European standard 3p wye that gives them the single phase L/N 220v. (also in the other Brit dominated places like NZ and Oz). It will also be rated at 50hz but I doubt a toaster wire heater cares about that.

[Scott Lurndal]

I suspect the 'simple adapter' refers to the OP pulling 120 from a four-wire 240 recep.

[gfretwell]

The OP already has that

[trader_4]

Silly me, I thought the thread was about the 240V to 120V adapter that the OP posted a link to at HD.

[gfretwell]

I was referring to the note you quoted and I assumed you were responding to.

[TimR]

Not being argumentative, asking because I don't know. Even though I should.

That circuit can supply 30 A at 240V on both hot legs.

The adapter will use one leg and get 120V. No problem, the treadmill is 120V. But the treadmill uses 17A. Is there still 30A available off just one leg? Or is there half of that, only 15A available?

[trader_4]

It can supply 30A at 120 too. With 240 the 30A goes from one hot to the other. With 120 it goes from one hot to neutral.

[Ralph Mowery]

I am not sure of the adaptor you showed a few days ago. However if the breaker is for 240 volts and 30 A then that is 30 A on each of the 120 V connections. So with the proper adaptor or rewiring the receptical you could use 2 devices that draw 30 amps at 120 volts. If one really gets technical, you probably should not draw but about 80% of that which is still plenty for your 17 amp treadmill.

Even the simplest of questions need to be asked when you are not sure. Even as I and another said, measure the adaptor to make sure you get near 120 V instead of near 240 V or just plug in a lamp and see if the bulb blows out or just burns normally before hooking up any expensive equipment.