Dryer plug incompatible w/outlet

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  #1  
Old 06-26-04, 10:19 PM
coryengel
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Question Need help: Dryer plug incompatible w/ outlet

I recently moved from a 7 year old house to a 30 year old house. The previous house had a new 4-prong dryer outlet, like this (I haven't figured out how to post images so if the images don't appear please use the links to illustrate the plug types):

http://cdvkiln.com/NEMA14_30Rx100.jpg


My "new" house has a 3-prong outlet, like this:

http://cdvkiln.com/NEMA10_50Rx100.jpg


I wasn't very observant when I looked at it, so when I went to buy a new cord for the dryer, I got a 3-prong dryer cord, like this:

http://cdvkiln.com/NEMA10_30Rx100.jpg


According to http://www.cdvkiln.com/menuelec.htm, the outlet in my new house isn't a dryer outlet at all, but rather a range outlet with a different amperage rating. It looks like a previous owner has jerry-rigged the darn thing with whatever 220v outlet they had laying around.

I think my options are:

1. Jerry rig my new dryer to work with the funky outlet. My concerns with this are (a) it just ain't right, and (b) if the amperage is whacked out I could have a problem.

2. Replace the outlet with a old 3-hole outlet, but I suspect you can't buy them any more.

3. Replace the outlet with a new 4-hole outlet (since I now have both 3-prong and 4-prong plugs handy). I've never worked with AC wiring before (other than shocking myself on a dryer element once) and I'm not really interested in doing that or paying someone else to do it.

Meanwhile, the dirty clothes continue to pile up.

What should I do?

I have a meter I can use to test the amperage (I think), since the type of outlet that's on it now makes me question whether the thing is even wired right for a dryer. I'm not sure how to test it however.
 
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  #2  
Old 06-27-04, 07:47 AM
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Hello: coryengel. Welcome to the Do-It-Yourself Web Site.

Since the question has to do with the electrical connection of the appliance and not a problem with the operation of the appliance, I moved it here, into the electrical forum topic. The electrical professionals will be best able to help you.

Use the reply button to add additional information or questions. Using this method moves the topic back up to the top of the list of current questions automatically.

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  #3  
Old 06-27-04, 08:02 AM
Doc Electric
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The wrong plug end

You're right, the outlet you have now is a range outlet, rated for 50 amps. It should be a dryer outlet rated for 30 amps. The breaker or fuse determines the amperage to the outlet, also the wire size. A normal dryer has a two 30 amp breakers or fuses and should have at least no. 10 gauge wire to the dryer outlet. If you have breakers they have to be mechanically linked for safety (if one trips they both shut off). Depending on your local city codes for wiring you may be able to put in a standard 3 prong dryer outlet and cord, but some cities require that you put in the four prong for extra safety. It is up to you what you do. Just remember that the center leg is the neutral and the outside two are the hot legs with 120 volts each. On the four prong plugs you have an extra wire that is a ground wire as well as the neutral ( even though they both end up back at the box on the buss bar where they are grounded. You might want to get an electrician just to be on the safe side and up to code. Doc E
 
  #4  
Old 06-27-04, 08:31 AM
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The very first thing to do is to go to your panel and determine whether the fuse or breaker that controls power to this receptacle is 30-amp or 40-amp or 50-amp. Let us know and we'll go from there.
 
  #5  
Old 06-27-04, 11:25 AM
coryengel
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40 amp, I think

I *think* it's a 40-amp breaker, but they breakers aren't labeled very well.

There's only two 30-amp breakers in the box, and they appear to go to the water heater and the air conditioner.

I have a multitester I can use to test whether the 40 amp breaker goes to the dryer outlet, but I'm not sure where to stick the probe(s). Assistance on that would help me confirm it's 40 amp.

Once I identify the correct breaker and confirm that it's not 30-amp, should I replace it with a 30-amp breaker, and then replace the outlet with a 3-prong outlet?

I'm not sure what kind of wire is in there, but I suspect it's not the kind that the 4-prong outlet requires.
 
  #6  
Old 06-27-04, 11:46 AM
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There's little room for guessing in electrical work, so we do need to make sure which breaker this is. You can actually stick the two probes of your voltmeter in any two of the three holes in the receptacle. If you probe the two slanted slots, you should get 240 volts. If you probe either slanted slot and the vertical slot, you should get 120 volts. Then turn off the breaker and verify that all is dead.
 
  #7  
Old 06-27-04, 12:13 PM
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Please know that the rating of the Branch-Circuit breaker, not the conductor size, determines the rating of the Branch-Circuit. If you re=place either a 40 amp or 50 amp breaker with one rated at 30 amps, you have "converted" the B-C to one rated at 30 amps, which is the "standard" rating for an electric-dryer B-C.

For testing, it's best to expose the receptacle connections so you can set the test-probes of a multi-tester directly across the receptacle terminals.You will "read" 220-volts Red-to-Black or 120-volts Red/Black to White.

It's best, if possible, to connect a 4-slot receptacle that is compatible with the existing 4-prong cord-plug.The Green terminal on the 4-slot receptacle is the Equiptment Grounding Conductor connection.

If the the cable that terminates in the outlet-box includes a bare Grounding conductor, that bare Grounding conductor is the EGC.If the Grounded (Neutral) conductor is either a White conductor or a un-insulated conductor, the Grounded conductor can be used to Ground the metal frame of the dryer.

I suggest you determine the type of cable that connects to the outlet-box, and the type of outlet-box, either metallic or non-metallic.

After we have recieved this info., we can proceed further.

Good Luck & Enjoy the Experience!!!!!!!!!!
 
  #8  
Old 06-27-04, 12:21 PM
coryengel
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Confirmed.

I confirmed that the dryer uses the 40-amp breaker I suspected, using the method John described.

So, it sounds like I need to buy a new circuit breaker and outlet.

The outlet is pretty hokey. What they did is use a flush-mount outlet, even though the wire is outside the wall in a metal conduit. They pounded a hole in the wall to flush-mount the outlet, and then jammed the conduit into the wall on the side. Looks like crap. When I replace it (assuming that's what you tell me to do!) I'm going to patch the hole and then use a surface-mount outlet like they should have in the first place.

I wonder why they had a 40-amp breaker in there? Could it be that the 30-amp breaker was getting tripped for some reason? Or more likely, maybe they just replaced an old 40-amp breaker with whatever they had lying around (which seems to be the method they used with the outlet).

Thanks for your help.

If replacing the breaker and outlet with a proper 3-prong 30 amp dryer outlet is the solution, then here's what it seems to me the next steps should be:

1. remove the 40 amp breaker
2. go to the store and buy a matching 30 amp breaker and 3 prong dryer outlet
3. replace the range outlet with the dryer outlet and patch the mess left by the previous owner
4. insert the 30 amp breaker and close the circuit
5. dry some clothes and become my wife's hero

If I'm missing something or if you have any tips on replacing the outlet/breaker, I'm all ears.
 

Last edited by coryengel; 06-27-04 at 12:42 PM.
  #9  
Old 06-27-04, 01:17 PM
coryengel
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Originally Posted by PATTBAA
It's best, if possible, to connect a 4-slot receptacle that is compatible with the existing 4-prong cord-plug.The Green terminal on the 4-slot receptacle is the Equiptment Grounding Conductor connection.

If the the cable that terminates in the outlet-box includes a bare Grounding conductor, that bare Grounding conductor is the EGC.If the Grounded (Neutral) conductor is either a White conductor or a un-insulated conductor, the Grounded conductor can be used to Ground the metal frame of the dryer.

I suggest you determine the type of cable that connects to the outlet-box, and the type of outlet-box, either metallic or non-metallic.
OK, I've got the outlet out (not easy since they foamed the thing into the wall instead of attaching it to a stud properly). The cable leading to the outlet has three conductors: white, black, and bare.

My understanding is that the new 4-prong outlet uses a different kind of cable. I assume I can attach a 4-prong outlet to the 3-conductor cable, and then use a 4-prong plug-in on my dryer. However, wouldn't that be kind of like attaching a 3-hole 110v outlet to an old 2-wire ungrounded house wire and calling it good? Is there any benefit to the 4-prong system without rewiring the circuit? Maybe I'm missing something.

I'm not sure what you mean about the metallic- or non-metallic outlet box. The box containing the outlet is plastic. Is there any other kind? Seems like a metal one would be kind of dangerous. In any case, what difference does it make?

So, should I install a 3-prong outlet or a 4-prong outlet? I'm all ready to go to Lowe's!
 
  #10  
Old 06-27-04, 01:56 PM
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Your mention of a 40-amp C-B, and your description of the cable, suggests that the existing Wiring Method is 8/2 Non-metallic cable. This type of cable would have been used , IF the installation was Code-compliant,for connecting a 2-wire ,220-volt load, a load that did not have a Neutral connection.

The problem with the cable you describe is the absence of an insulated Grounded ( Neutral, White-wire) conductor for a 3-wire ( Black, Red, White) connection. The Code allows using an un-insulated Grounded conductor for a dryer/range connection if the cable is pre-existing, and the cable is Type SE service-entrance cable. (Art 250.140 (3) ).

A metallic O-B is often prefferable because it it can be used either flush/surface, and with 1 or 2-gang "rough" covers (flush) and for different-sized "Austin" covers (surface).
 
  #11  
Old 06-27-04, 02:18 PM
coryengel
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Originally Posted by PATTBAA
The Code allows using an un-insulated Grounded conductor for a dryer/range connection if the cable is pre-existing, and the cable is Type SE service-entrance cable. (Art 250.140 (3) ).
OK, I *think* I'm able to follow all that, but what I need to know is:

1. How can I tell if if the cable is "Type SE service-entrance cable"?

2. Do I use a 3-prong outlet or a 4-prong outlet? I have both kinds of plugs that I can connect to the dryer, so my convenience isn't a factor.
 
  #12  
Old 06-27-04, 02:47 PM
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Type SE cable would not have an insulated White conductor. The 2 insulted conductors would be 2 Blacks, or 1 Black & 1 Red.

The conductors would be stranded, not solid.

The Neutral conductor would have the appearce of individual "fine" wires that had been twisted together to form a single conductor.
 
  #13  
Old 06-27-04, 02:56 PM
coryengel
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Originally Posted by PATTBAA
Type SE cable would not have an insulated White conductor. The 2 insulted conductors would be 2 Blacks, or 1 Black & 1 Red.
OK, so I don't have Type SE cable, and the circuit isn't up to code. Here's what I'm going to do:

1. replace the 40 amp breaker with a 30-amp

2. replace the range outlet with a 3-prong dryer outlet

3. put the 3-prong dryer outlet on the dryer

4. hope my house doesn't burn down

5. have an electrician do it right the next time I have one at the house on another project
 
  #14  
Old 06-27-04, 10:48 PM
coryengel
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Done.

Well, for better or worse, I done it, and I've got a load of whitie tighties drying right now.

I put in a new 30 amp breaker, 30 amp 3 prong outlet, and used the wiring already there. The next time I have an electrician in the house I'll have him redo the whole thing and bring it up to optimum specs. It worked at 40 ams with the range outlet for years, so I figure that at worst, it's no worse off now than it was before.
 
  #15  
Old 06-28-04, 07:47 AM
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If you are connecting a 3-wire cord to the dryer, please be certain that the metal frame of the dryer is "Bonded" to the Neutral conductor at the point where the Neutral conductor terminates inside the dryer.

If this Bonding Jumper is absent, you'll be operating the dryer in an un-safe condition.
 
  #16  
Old 06-28-04, 06:23 PM
coryengel
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Originally Posted by PATTBAA
If you are connecting a 3-wire cord to the dryer, please be certain that the metal frame of the dryer is "Bonded" to the Neutral conductor at the point where the Neutral conductor terminates inside the dryer.
Thanks for the tip. Currently, the center/neutral lead on the power cable is connected to the center terminal in the dryer. The back of the lead is connected to a white wire that leads into the dryer I-don't-know-where. (It goes into a bundle and becomes untrackable without disassembling the whole thing.) I don't have a schematic of the dryer handy (and I'm not sure I could read it if it did), so I don't know where this goes.

There are numerous green screws on the dryer's chassis with green wires connected to them; one of these is accessible from the outside adjacent to the 6-inch access panel that lets me access the power cable connections.

Are you suggesting I run a jumper from the neutral to the green screw? I'm not sure I understand. None of the internal wiring of the dryer has been modified from the factory; shouldn't that be grounded already?

Thanks for your patience.
 
  #17  
Old 06-28-04, 09:21 PM
doingitmyself
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Originally Posted by coryengel
Are you suggesting I run a jumper from the neutral to the green screw?
Yes!

With the 3-wire system, the neutral (white) and the ground (green) should be bonded inside the dryer.

This is because there's no grounding wire running from the panel to the receptacle in the 3-wire system.

If you had a 4-wire from the panel to the receptacle (along with both the 4-slotted receptacle and the 4-prong cord plug), then you would not bond the neutral and ground inside the dryer, since then, there would be a 4th (probably bare) grounding wire running to the receptacle from the circuit breaker panel.
 
  #18  
Old 06-28-04, 11:57 PM
coryengel
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Thanks!

Thanks. I really appreciate all the help I've gotten here.
 
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