electric clothes dryer

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joem1

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As a homeowner who does most of the maintenance in our building, I am now trying to hook up an electric dryer. The manufacturer installation manual shows two hookups at the machine: a 3-wire power cord connected to 3 terminals Red, White, and Black (with a green round wire connected to the frame of machine). The other hookup is for a 4-wire power cord, connected to same 3 terminal, but the 4th green ground on mahine frame is now connected to white-neutral terminal, and green wire from power cord is connected to frame of machine. Manual states that 4-wire connection is for mobile homes.
I ran a No.10, 3-wire armored cable from circuit panel to a 4-wire receptacle at machine, and hooked up a 4-wire power cord, as stated in install manual. I spoke to a few electricians who gave me different information:
1. You must have 4-wire all copper, 3 insulated, and one bare copper, to meet Code requirement. ( But I do not want to run Romex in an older house through walls).
2. Do a 3-wire power cord, as per install manual, and and 3-wire armored cable, with 3-wire receptacle.
3. Leave the 4-wire power cord and 4-wire receptacle, and 3-wire armored cable (I have already installed). But add a grounding strap from 4th green terminal on the rececptacle to the receptacle metal/outer armored cable.

I'm not sure what is best to do, and how to connect at circuit panel.
Any information is appreciated. :confused:
 
Re: electric clothes dryer

From the NEC
250.140 Frames of Ranges and Clothes Dryers. This section shall apply to existing branch-circuit installations only. New branch-circuit installations shall comply with 250.134 and 250.138. Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be grounded in the manner specified by 250.134 or 250.138; or, except for mobile homes and recreational vehicles, shall be permitted to be grounded to the grounded circuit conductor if all the following conditions are met.
(1) The supply circuit is 120/240-volt, single-phase, 3-wire; or 208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system.
(2) The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum.
(3) The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE service-entrance cable and the branch circuit originates at the service equipment.
(4) Grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment.
From the NEC Handbook
Section 250.140(4) applies only to existing branch circuits supplying the appliances specified in this section. The grounded conductor (neutral) is no longer allowed to be used for grounding the metal non?current-carrying parts of the appliances listed in 250.140. Branch circuits installed for new appliance installations are required to provide an equipment grounding conductor for grounding the non-current-carrying parts.
Caution should be exercised to ensure that new appliances connected to an existing branch circuit are properly grounded. An older appliance connected to a new branch circuit must have its 3-wire cord and plug replaced with a 4-conductor cord, with one of those conductors being an equipment grounding conductor. The bonding jumper between the neutral and the frame of the appliance must be removed. If a new appliance is connected to an existing branch circuit without an equipment grounding conductor, where the neutral conductor was previously used for grounding the appliance, a bonding jumper must be installed at the appliance terminal to connect the frame to the neutral.
The grounded circuit conductor of an existing branch circuit is still permitted to be used to ground the frame of an electric range, wall-mounted oven, or counter-mounted cooking unit, provided all four conditions of 250.140 are met. The grounded circuit conductor is also permitted to be used to ground any junction boxes in the circuit supplying the appliance, and a 3-wire pigtail and range receptacle is permitted to be used, even though the circuit to the receptacle contains a separate equipment grounding conductor.
Where service-entrance cable was previously installed, an uninsulated covered neutral conductor was allowed. However, the circuit was required to originate at the service equipment to avoid neutral current from downstream panelboards flowing on metal objects, such as pipes or ducts. Exhibit 250.51 shows an existing installation in which Type SE service-entrance cable was used for ranges, dryers, wall-mounted ovens, and counter-mounted cooking units. Junction boxes in the supply circuit were also permitted to be grounded from the grounded neutral conductor.
*****************************
The grounded conductor is the white or neutral wire. The ungrounded conductors are the phase conductors or the hot wires which are normally red and black. The grounding conductor is the green or bare wire.
 
Re: electric clothes dryer

Joe, you make this sound as though it is a multi family building. If this is the case, you should let a professional do the wiring.

If this was your own home exclusively you would have every right to do this.

Roger

[ June 25, 2003, 01:03 PM: Message edited by: roger ]
 
Re: electric clothes dryer

I am a homeowner as well, and like to do my own maintenance and work around the house. It is a good for my finances and self-pride to be able to complete tasks on my own.

The key element is to know when you are getting in over your head. Im sure at first thought this was going to be any easy job without much issues to contend with. However, you have hit a snag and are getting several different answers from several different persons, and now probably going to spend more time, effort, and money to have simply hired this work out.

Save your money, save your property, save your life and hire a licensed professional electrician. Whether this is your own home or not, you owe to to your family and neighbors to not put them at risk of any hazards or fires that could be results of your incompliant work.

I commend you on your efforts to educate yourself and for not just wiring it up the most convienent way for you. I mean no offense with this post and in no way calling into question your abilities or qualifications. Please take my advice with great consideration. :)
 
Re: electric clothes dryer

WOW! Good catch Roger, I read right through that fact. I suspect he doesn't have enough money or insurance to cover anything done wrong in this situation, especially since he is not considered a qualified person. Since I let my license, bond, and insurance go, you couldn't pay me enough to do any electrical work for someone else. :eek:
 
Re: electric clothes dryer

Dryers usually come with the neutral bonded to the dryer case so that if the wiring is 3-wire from an older installation, you are allowed to use the grounded conductor (neutral) as the grounding conductor as allowed in older Codes.

But if you are running the wiring, it must be 4-wire, and you must detach the bonding conductor in the dryer which goes to the case and connect it back to a neutral screw, nullifying the bond.

Instructions with the dryer tell you to do this.

I have seen multiple dryer installations where the N/G bond was not removed, even though they were 4-wired.

This resulted in neutral current from the dryer traveling through the case to the steel mounting rails, through the rails to the washer cases, and then back to the panel in their grounding conductors and water pipes (copper).

This splitting of the neutral return path set up a large magnetic field which the housing authority wanted to get rid of. Solution:
remove the N/G bond in the dryers as per installation instructions.
Karl
 
Re: electric clothes dryer

The other hookup is for a 4-wire power cord, connected to same 3 terminal, but the 4th green ground on mahine frame is now connected to white-neutral terminal, and green wire from power cord is connected to frame of machine.
Click to expand...
These instructions are not correct. With a 4 wire cord there should be no connection between the machine frame and the white wire.
Don
 
Re: electric clothes dryer

ok, after reading through all the above, it still doesn't quite answer my situation.

1) single family dwelling (approx 15 yrs old), newly purchased.
2) existing circuit is a 3-wire 10 AWG
3) wall receptacle is a 4-wire (GND is not wired)
4) Dryer is internally bonded (GND -> Neutral)

My options (I think)
1) don't worry, be happy.... (I don't like this one - just 'cause it's not right).

2) route a new GND wire and break the internal bond. If I do this, are there any issues with routing the GND wire (proximity to the existing circuit cable)? Does it have to go back to the breaker panel or can I bond it to nearby plumbing?

3) change out the 4-wire receptacle for a 3-wire receptacle and call it an older existing circuit (As I'm sure it was originally).


I think it's "mostly" safe. I just want to know the best way to get rid of the "mostly" in that statement.
 
Re: electric clothes dryer

Your option #3 is the only way this is going to be code compliant. Note I said code compliant, not necessarily safe. If it were me I would run a new cable, there's always a way.

-Hal
 
Re: electric clothes dryer

"I ran a No.10, 3-wire armored cable from circuit panel to a 4-wire receptacle at machine, and hooked up a 4-wire power cord"

I see a problem in using number 3
What year code was in effect when you ran this cable ? If 4 wire was required and you ran 3 wire then only correct thing is to re run with correct wire.Who all uses this dryer ?
 
Re: electric clothes dryer

thanks for all the replies. As far as "legal code" and timing, I'm ok with the three pole solution using the existing wire.

However, if there is real safety issues that make a 4-wire solution better, I'd like to hear your comments.

tia
Keith
 
Re: electric clothes dryer

I ran a No.10, 3-wire armored cable...

What year code was in effect when you ran this cable ? If 4 wire was required and you ran 3 wire then only correct thing is to re run with correct wire.

Nothing wrong with using 10/3 AC.

-Hal
 
Re: electric clothes dryer

Isn't 10-3 AC two conductors plus ground(black, white, green), as opposed to 10-3 NM-B that has three conductors (black, red, white, bare) plus ground? I think that's the part of this debate.

You just had to mess with it, ey? :D

The nuts and bolts of it is, since your existing installation had a three prong receptacle, code would have allowed you to install a three prong cord on your new dryer to utilize it. That's why ranges and dryers are sold with the jumper from ground to neutral installed, and we have to take that jumper out when we install a new, 4 prong cord.

If you install a new branch circuit, you have to abide by the current code in your neck of the woods, probably 2002, which would require two hots, a neutral, and a separate ground.

The spirit is, is you install a four-prong receptacle where your three prong was and make no other changes, the wall is lying to you and future residents based on external appearances that "it is grounded." An installer of a third "new" dryer, unaware that the wall is lying to him, will remove the bonding white-to-green jumper from the appliance, removing even the lesser grounding protection of neutral provides.

I just said the same thing these guys are saying, in a 14th different way. That's why we're professionals and people pay us a lot of money to just shut up, put in new and do it right! :D

Kudos for searching and finding this year-old post! Charlie's reprinting of the code was sure easier than looking it up! :D
I didn't even realize that until I wrote all that out...
 
Re: electric clothes dryer

Originally posted by georgestolz:
Isn't 10-3 AC two conductors plus ground(black, white, green), as opposed to 10-3 NM-B that has three conductors (black, red, white, bare) plus ground? I think that's the part of this debate.
Click to expand...
10-3 AC is armored cable with white, black, red. no grounding conductor, the armor is the grounding conductor.

10-3 NM-B (romex) white, black, red, bare.

Either of these cables will be fine for a 4 wire outlet.
 
Re: electric clothes dryer

Are you sure about that Bob? I don't use AC much but I have 12-3 MC here that has a jolly green wire in it.
 
Re: electric clothes dryer

Yes I am sure. :)

AC Cable is a different product than MC Cable.

There is also Hospital grade AC with an insulated ground.

The majority of my work is with MC cable.

[ December 05, 2004, 02:29 PM: Message edited by: iwire ]
 
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