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What kind of Wire should I use to wire a dryer from an outside breaker box?

OK I have already done this project but I'm having doubts about its safety.

I bought NM 10/2 cable after talking with a sales person at lowes and a so called electrician who was shopping there at the time. I told both guys that my breaker box is outside and I would be drilling a hole for the cable to run into the house and I wanted a conduit to cover the wire once its was cut to length and ready to be installed (how many houses do you see with wires just running from the breaker box without covering on  the outside of houses). Both told me I didn't need to cover the wire that the 10-2 wire had enough insulation on it to be fine. Well i'm a perfectionist and I want my project up to code. So doing further online searching I found out I maybe should be using UF wiring since its it is better protected from heat and wet conditions ( I didn't know there was indoor and outdoor wiring at the time of purchase). 

I haven't changed out the wire since I already cut it before finding out it might not be OK for this project but I did go back and encase it in liquid-tight non metal flexible conduit and I used water tight seals both ends.. I have grounded the metal box I used to install the dryer outlet and 30 amp breakers that used two spaces in my breaker box and a 30 amp three prong dryer plug since the dryer I bought was a 3 wire dryer. My concern is should I redo this project with outdoor rated 10/2 wiring just to be safe or have my made the wiring safe by using the liquid tight conduit? I still want it to have the same setup, total wire that was used was a little less than 6 inches from breaker box to outlet. I also clamped down the conduit every 12 inches to secure it to the wall. I'll be pissed if I have to do it again and stuck with indoor wire I don't need because I got bad advice but better safe than sorry.  Thanks in advance for any assistance you can give, 

Gigi in NC
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Posted 2016-10-04T03:41:02+0000  by Gabbieboo Gabbieboo

I don't want to be the bearer of bad news but you're going back to the store because there is another issue with your wiring job.  Current code requires a three wires (plus ground) for a new circuit for a dryer.  In years past it was acceptable for the equipment ground and neutral wire to be shared but that has changed.  Unfortunately it doesn't matter what kind of plug is on the dryer, the determining factor is that circuit supplying the dryer is new.  So you will need 10/3 (plus ground) cable.  You'll also need a new, 4-prong plug for your dryer.  Follow the dryer manufacturer's instructions for installing it.

Outside the house is almost always considered a damp or wet location, even if conduit is used and therefore NM-B cable can't be used.  One should never consider conduit to be "waterproof."  So you should use UF-B cable or individual wires rated for wet locations (typically type THWN or THWN-2). Your are correct in that your cable needs protection from physical damage, although I'm not sure that a flexible conduit is an approved choice in this situation.  Rigid conduit (either steel or schedule 80 PVC) would be.

When in doubt, don't assume that store employees, customers, or strangers in online forums know what they're talking about.  While they may, it's always better to consult a licensed electrician.

Just like Home Depot, Lowe's has a pretty liberal return policy, even if it's not advertised.  If there's an issue returning the cable, just talk to a manager.
Posted 2016-10-04T07:16:42+0000  by Adam444

Thanks for the reply. I had heard that I should use a four wire setup since it was updated for better protection, of course this was after I had done the project.  The house was build in the 1950 so I thought I could get away with using the 3 wire setup since most of the plugs in the home aren't grounded and only have two prong outlets.

Ok so if I redo the dryer/outlet with the right stuff inside my breaker box I don't see a neutral bar only the ground bar. So my last question is where would I attach the neutral wire? Thanks in advance.

Gigi in NC 
Posted 2016-10-05T15:00:25+0000  by Gabbieboo

Sorry, I missed your reply.

In your case, both the neutral wire (white) and ground wire would be attached to the same bus bar.  If you had a sub-panel, then there would be two bars, one for the neutral and the other for the ground.

As for the code, it's always the code in force at the time the work is done.  Old work is "grandfathered" and generally you don't have to make changes unless it's part of a larger project.  In the case of your dryer, had an existing 3-wire plug been there, then it would have been acceptable to leave the circuit alone and just install 3-wire plug on your new dryer.

The reason for the additional wire is that a 240 volt circuit doesn't require a neutral wire.  With dryers (and other large appliances) that use a 240 volt circuit, they often have control circuits or even light bulbs that require a neutral wire to function.  In the past, the equipment ground and neutral were shared.  The new, 4-wire requirement is somewhat safer as electricity has a clear path to ground should the metal frame of the appliance become energized.
Posted 2016-10-07T18:57:26+0000  by Adam444
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