how to wire a dryer

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  #1  
Old 01-22-05, 05:29 PM
benjos
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how to wire a dryer

does a 240V 30A 2 pole 3 wire receptacle need a fourth wire for ground/neutral? what is the difference between ground and neutral? what is the risk of not having that fourth wire? the plug on the dryer only has three wires. does this sound safe? thanks
 
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  #2  
Old 01-22-05, 06:03 PM
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The neutral is the return path for the 120 volt portion of the dryer circuit. In a dryer the light, the timer, and the the motor are typically 120 volts, while the heater is 240 volts.

The ground is the safety and connects to the metal shell of the dryer.

If you are installing a new circuit then the new circuit must be a four wire circuit. Existing circuits that are three wire are allowed to remain as three wire.

The dryer will have separate directions for wiring as a three wire device and as a four wire device. These directions must be followed.

If properly connected, a three wire dryer is almost as safe as a four wire dryer. The only difference with a three wire circuit is that, the metal shell of the dryer and the return neutral in the dryer are connected to the ground wire.
 
  #3  
Old 01-22-05, 06:11 PM
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240 volt circuits need no neutral at all, just two hots and a grounding wire. Circuits which provide both 240 and 120 need four wires, two hots, a neutral and a grounding wire.

Code grants special exceptions for dryer and range installations prior to 1996 that meet a certain set of conditions. This exception allows one wire to serve as both grounding and neutral, but it applies to these two appliances only, and nothing else. It also does not apply to any circuit installed or modified after 1996.

You asked the difference between ground and neutral. That's a heavy question which would take a book to fully explain. But the short answer is that the neutral carries current during normal operation, but the grounding wire carries current only in the event of a fault. Also, the grounding wire is connected to the chassis of the appliance but the neutral is not.

Dryers with 4-wire circuits are safer than dryers with 3-wire circuits, but there are a hundred million dryers with 3-wire circuits still running in this country. The principal danger is that if the dryer experiences an open ground/neutral fault, the chassis of the dryer can be energized to 120 volts. I don't think you need me to tell you that this is very bad. The special set of conditions I mentioned earlier are designed to minimize the chances of an open neutral fault on the dryer circuit (which are quite common on other circuits in your house).

If practical, change out your 3-wire dryer circuit for a 4-wire circuit. In many homes however, that's not very practical due to cost. Code only requires you to do this upgrade if you make any changes to the circuit (such as relocating your dryer).
 
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Old 01-22-05, 06:54 PM
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Originally Posted by John Nelson

If practical, change out your 3-wire dryer circuit for a 4-wire circuit. In many homes however, that's not very practical due to cost. Code only requires you to do this upgrade if you make any changes to the circuit (such as relocating your dryer).

John,

I've wondered about this for a while. If a dryer fed by a 3-wire circuit is relocated, and the old three wire 10-3 (without ground) is long enough to reach and in good shape, would code allow reusing that wire, and robbing a ground from a nearby grounded receptical? Say the nearby receplicle is 12-2 wg romex fed from a 20amp breaker, is that OK or does the ground have to also be #10 wire?
 
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Old 01-22-05, 07:11 PM
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It's a gray area. You'd have to ask your inspector.

But no, the #12 isn't big enough.
 
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Old 01-22-05, 07:34 PM
benjos
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where's the ground go?

if the dryer has a 3 wire plug and a 4 wire circuit runs to the outlet, is it legit/safe to ground to a metal receptacle box?
also, it is feasible to run a 4 wire circuit. thanks everybody.
 
  #7  
Old 01-22-05, 08:02 PM
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By 4 wire I assume you mean a black,a red,a white,the ground wire is not counted.Yes you should ground the box if 3 wire is used.Its against code to use the ground as a neutral.Even if you still only use a 3 wire receptacle I would run the 3 wire from the panel.This way you'll be ready when it comes time to upgrade the dryer.
 
  #8  
Old 01-23-05, 04:00 PM
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If your asking about the cord

from the dryer itself to the wall, then you need a new cord. You should be able to easily find both 3 and 4 wire cords in the hardware store. This is a link that shows how to connect the new cord to the dryer: http://www.american-appliance.com/se...dryer_cord.htm


Hope this helps!
 
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Old 02-01-05, 10:59 PM
catpu
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I have a similar question

Originally Posted by chirkware
John,

I've wondered about this for a while. If a dryer fed by a 3-wire circuit is relocated, and the old three wire 10-3 (without ground) is long enough to reach and in good shape, would code allow reusing that wire, and robbing a ground from a nearby grounded receptical? Say the nearby receplicle is 12-2 wg romex fed from a 20amp breaker, is that OK or does the ground have to also be #10 wire?

I have a similar question. I have a 3-prong dryer outlet that is fed by wires that go thru metal conduit (EMT) all the way to the service panel. If I were moving the outlet would it be it okay to ground a new 4-prong receptacle to the box/conduit? Any arguments / new codes against doing so? There are a number of 110 receptacles in my house that are grounded this way. Thanks.
 
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Old 02-02-05, 02:11 AM
catpu
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Originally Posted by catpu
I have a similar question. I have a 3-prong dryer outlet that is fed by wires that go thru metal conduit (EMT) all the way to the service panel. If I were moving the outlet would it be it okay to ground a new 4-prong receptacle to the box/conduit? Any arguments / new codes against doing so? There are a number of 110 receptacles in my house that are grounded this way. Thanks.
I should add that i would like to re-use the existing wire as well.
 
  #11  
Old 02-02-05, 06:06 AM
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Your ok because you already have an equipment grounding conductor, the conduit itself. I assume you have a metal receptacle box. Make up a pigtail (short piece of #10 wire, either bare or green insulated) and screw it securely to the box, connect this to the ground lug on the receptacle.
 
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