How to tell NEMA 10-50 from 10-20?

[RDoc]

We're in a rental house we go to every year that has an electric dryer on a circuit with a 240 30A breaker. The plug is a 3 bladed one, all straight, but I don't know if it's a 10-50 (scary) or a 10-20 (weird).

It's there a simple way to tell them apart?

 

[qwk]

No such thing as a 10-20. If it has 3 flat prongs, and is 240V, it sounds like a 10-50.

 

[scottf200]

We're in a rental house we go to every year that has an electric dryer on a circuit with a 240 30A breaker. The plug is a 3 bladed one, all straight, but I don't know if it's a 10-50 (scary) or a 10-20 (weird). It's there a simple way to tell them apart?

If it is on a 30A breaker then why don't you think it is a 10-20? You could also check the wire gauge out of the box or by opening the receptacle.

Some references:
http://www.powerstream.com/NEMA-plug-reference.htm
http://www.nooutage.com/nema_configurations.htm
https://www.google.com/search?q=30+*+80%

 

[RDoc]

If it is on a 30A breaker then why don't you think it is a 10-20? You could also check the wire gauge out of the box or by opening the receptacle.

Some references:
http://www.powerstream.com/NEMA-plug-reference.htm
http://www.nooutage.com/nema_configurations.htm
https://www.google.com/search?q=30+*+85%
View attachment 33506

The diagrams of the two look the same to me.It's there a way to distinguish the plugs from each other?

 

[RDoc]

It's a10-50. The difference between the two is size, the 10-20 is much smaller, about 1 1/2 inch diameter. Apparently using a10-50 plug on a 30 amp breaker was legal and common for dryers.

 

[scottf200]

It's a10-50. The difference between the two is size, the 10-20 is much smaller, about 1 1/2 inch diameter. Apparently using a10-50 plug on a 30 amp breaker was legal and common for dryers.

I would check the wire gauge to determine what amperage you should draw. They may have put in just large enough wire to run the dryer on that 30 amp circuit.

 

[FlasherZ]

Pay no attention to those amperages listed there. They're close in some regards, but they aren't quite right when you're looking at the larger numbers (it makes the assumption you're using the 60 deg C column, almost everything nowadays is 75 deg C rated, except Romex/NM-B cable).

 

[qwk]

It's a10-50. The difference between the two is size, the 10-20 is much smaller, about 1 1/2 inch diameter. Apparently using a10-50 plug on a 30 amp breaker was legal and common for dryers.

Wow. These must be super rare. I have never heard of one. It looks like it's an older version of the 5-20/6-20 outlet.

 

[RDoc]

Even at 24A, an overnight charge will produce a full battery to get home.

I'm thinking about getting the 10-30 adapter and building a 10-50 male to 10-30 female connector to plug into. I believe that will take care of the ground/neutral issue and limit the current to 24A which I don't want to exceed.

Now all I need is my X!

 

[Cosmacelf]

Can you take a picture of the outlet and post it? But yes, making a 10-50 to 10-30 adapter and the using Tesla's 10-30 adapter would make sense.