240v 20a 3-prong outlet wiring with a metal outlet box

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  #1  
Old 07-01-11, 06:02 PM
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240v 20a 3-prong outlet wiring with a metal outlet box

We recently had a residential house rewired with a new drop and panel. I just found out the dryer was not hooked up correctly and so went to check the other 240v 3-prong outlet powering a large window a/c unit. My concern is they have the ground bare wire running to the outlet AND grounded to the metal box. I tested from one hot lead to the metal box and its reading 120v. The white neutral wire is capped off (but connected to the neutral bar inside the panel). The other two hot leads (black and red) are hooked up correctly and are receiving voltage correctly. Is this wired safely? Or should the neutral be connected to the outlet and the ground connected to the metal box?
 
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Old 07-01-11, 06:13 PM
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A window AC uses 240v not 120/240v as some appliances like dryers do. No neutral is needed. Only the 240v line and ground for safety. Metal boxes should always be grounded.
 
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Old 07-02-11, 12:40 AM
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Do you have 3 wire or 4 wire dryer hook up both are diffrent in connection and with large window shaker { Window A/C unit } when wired in stragiht 240 volts it is normal as Ray describing and give you a clear details on it.

And with any metal box we have to run the ground wire to them and bond it together with a jumper pigtail or other means depending on conductor size and numbers in the box.

{ just give you a head up if you have old school BX cable never hook them up with plastique box unless you have bonding K.O. }

Merci,
Marc
 
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Old 07-02-11, 09:20 AM
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Our dryer has a 4 wire hook up. Our old one quit working so we bought a new (used) one that wasn't turning on either. After some looking at it, the dryer neutral was not hooked in the panel, and the ground was not hooked up at the outlet. So they had the old 4 wire dryer running just off the two hot leads! I don't even know how the old one was working lol! I connected the neutral in the panel and the grounded at the outlet, and all seems well with it now. So that's a little background on why I thought the a/c unit might have been incorrectly wired.

Also, the a/c outlet ground is pigtailed and connected to the metal box. That you guys for the helpful info! Just wanted to make sure it was as safe as possible.
 
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