Electric dryer plug melted w/o blowing fuses

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  #1  
Old 05-12-05, 11:34 AM
mvigor
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Electric dryer plug melted w/o blowing fuses

Hello all! My Electric Dryer's big 220 plug has given me trouble twice before and this is the third time I've ruined one. It got so hot a couple nights ago that I could smell the burning plastic from the next room and when I checked on it, it was smoking. It took an hour to cool down before I could even unplug it.

Obviously I have a problem. I plan on taking no more chances and I'll be replacing the dryer and the wiring all the way from the main fuse box.

My question is simply...

How in the world could the cord get that HOT without blowing the fuses? I thought that surely my fuse box would protect me from a fire. Why didn't it?
 
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  #2  
Old 05-12-05, 11:46 AM
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In some older homes with fuse boxes the electric range and dryer are connected directly to the main fuse and do not have their own fuses. Sometimes they will also be connected directly to the incoming service with just a pullout disconnect (unfused). Do either of these situations apply to you?

Another thing to check: if the dryer does have a fuse, did someone bypass it by putting a piece of metal (like a penny) in behind the fuse?

Finally, is the fuse too big for the wire? A dryer should only have a 30A fuse and be connected with at least 10 gauge copper or 8 gauge aluminum.

Good idea to replace everything lest you start a house fire!
 
  #3  
Old 05-12-05, 12:04 PM
mvigor
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Originally Posted by ibpooks
In some older homes with fuse boxes the electric range and dryer are connected directly to the main fuse and do not have their own fuses. Sometimes they will also be connected directly to the incoming service with just a pullout disconnect (unfused). Do either of these situations apply to you?

Another thing to check: if the dryer does have a fuse, did someone bypass it by putting a piece of metal (like a penny) in behind the fuse?

Finally, is the fuse too big for the wire? A dryer should only have a 30A fuse and be connected with at least 10 gauge copper or 8 gauge aluminum.

Good idea to replace everything lest you start a house fire!
The house was built in 1965 with a 4-fuse service, which at some point had two more fuses added into knockouts on the left and right side, and then in 1975 a smaller 4-fuse baby box was added too.

When I moved in, I never was able to determine by removing fuses which two ran the dryer...I'll have to take the face plates off the fuse boxes tonight and have a look at where the wires run. Luckily all the wires are exposed in the basement so I should be able to follow everything easily.

I do know that none of the 10 fuses in the house are bypassed and the two fuses that I have suspected of running the dryer circuit had one 25A and one 30A fuse respectively. I removed them while waiting for the plug to cool off and that was almost 2 days ago. I haven't noticed anything else that _doesn't_ run with the fuses removed, but I also haven't had furnace or AC on.
 
  #4  
Old 05-12-05, 12:05 PM
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A poor connection between the plug and the receptacle will generate heat. This will not increase the current so the breaker/fuse will not blow.
Unless you see damage to the cable, replacing the receptacle and the dryer cord should resolve this problem.
What was done in the past to solve the problem?
What size is the cable? It should be #10
What size is the fuse/breaker? It should be 30 amp double pole.
 
  #5  
Old 05-12-05, 12:21 PM
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It seems like it has to be more than a loose connection if the OP has melted three receptacles. I suppose each one could have been loose, but that doesn't seem probable.
 
  #6  
Old 05-12-05, 12:41 PM
mvigor
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I'm still using the same female wall receptacle that was already installed when I bought the house. Judging from the look of the wire running from the receptacle to the fuse box it's probably 30 years old. It didn't get damaged the first two times, or at least I didn't think it was.

I've melted 3 plug ends now, and this time was by far the worst so I will *have* to replace the receptacle along with the plug. I still have enough dryer cord wire to cut off a foot and try again, but at this point I have the nagging attitude of "don't kill your family to save $500"
 
  #7  
Old 05-12-05, 01:13 PM
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Well in that case, I agree with joed that the cause was a loose terminal in the receptacle. Replace the receptacle and dryer cord, and look inside the dryer wiring box to make sure everything looks okay. Trace the cable back to the panel box and closely inspect it with a flashlight. If you don't see any burn marks or melting, then the cable is okay and doesn't need to be replaced.
 
  #8  
Old 05-12-05, 09:46 PM
mvigor
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Well I had a better look at everything. With the cover off the fuse box I verified that the dryer receptacle was fused with the two fuses in question and that they hadn't been bypassed. Everything in the box looked pretty good.

Further inspection of the wire providing service from the fuse box to the receptacle showed that the old insulation was worn and crumbling. This wire was run over ductwork and left to rub, then nailed across the floor joists overhead with all-metal nail straps.

By far the worst looking part was inside the receptacle! The pin that had done most of the melting and burning was spread open like you wonderful folks suggested. But the entire box was rusting and corroding, including the exposed parts of the copper wire.

Some thought reminded me that when I moved into the house there was a preexisting leak in the rain gutter right outside directly over where this receptacle sat. It is screwed into metal wall anchors which themselves are sunk into holes drilled in the concrete blocks and when that gutter leaked during a strong rain, water came into the basement right through those holes.

I wish my digital camera was working because the box was just a mess. You all did save me from throwing out a suspicious dryer and I saved $300 there.

I guess I'll mount the replacement on a board. Thank you!!
 
  #9  
Old 05-13-05, 03:38 AM
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I'm not sure if you are planning to run a new cable from the fuse box to the dryer, but if you do, you need to run 10-3wg (black, red, white, bare)...The old circuit no doubt was three wire (no ground). Todays dryer circuit must be four wire...It's no harder to run anyway. Just one extra connection at the fuse box, a 4 prong receptical, and a 4 prong dryer cord. You'll need to remove the bonding strip that connects the dryers chassis to the neutral on its current cord (they used to "ground" the dryer chassis to neutral since there was no ground). Be sure to use 30A fuses to protect the circuit after you run this cable.

Good luck!
 
  #10  
Old 05-13-05, 06:26 AM
mvigor
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Ok, thank you for letting me know that. Is grounding the bare wire to a water pipe acceptible or would following proper code have me do it another way?
 
  #11  
Old 05-13-05, 07:11 AM
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NO NO NO. Do not ground to a water pipe. This invites trouble.
 
  #12  
Old 05-13-05, 07:29 AM
mvigor
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Ok so I assume I'll be drilling a hole in my wall and installing a grounding rod outside the house, then running a wire from the rod to the little fuse box. This trip to Home Depot is going to be a learning experience because I don't even know what this stuff looks like.

If the fuse box is old enough it won't have a grounding screw/rail/whatever so I'll have to replace the box as well I suppose.

I definitely want to do it right, and I know that doing it myself will automatically be over $100 cheaper than hiring it done, so no matter what I have to buy I'll be way ahead in the long run. LOL. My wife was ready for the expense of a new dryer so she'll be happy with anything under a couple hundred bucks. I guess this way I'll be grounded and ready when my 1975 A/C unit quits on me. *knock on wood*

So does electrical code dictate grounding the original main box AND the little offshoot I'll be working in, or can I just ground the baby box?
 

Last edited by mvigor; 05-13-05 at 07:45 AM.
  #13  
Old 05-13-05, 07:45 AM
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You need to run the ground wire back to the main panel box and no where else. The white neutral wire and green (or bare) ground wire will both attach to the neutral bus in the main panel.
 
  #14  
Old 05-13-05, 07:49 AM
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Your fuse box should already be grounded to the water incoming pipe, and possibly to a ground rod. Your dryer will connect to the bar in the main panel where this ground connects. This is usually the same place where neutral wires connect, but not always.

If your fuse box is not grounded, then I would suggest calling in an electrician to ground it. Better yet, replace the fuse panel with a circuit breaker panel. Grounding is something that must be done properly.
 
  #15  
Old 05-13-05, 07:50 AM
mvigor
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Awesome! I just connect the new green ground wire to the white bus in the main fuse box and then replace the runner wire from the main box to the little one with a short piece of the same 220 wire I'll use to run the new dryer receptacle. Then they'll both be grounded. Excellent.

As for it already being grounded, perhaps it is, but none of the house was wired up with grounded circuits. I'll have a good look for the ground on the main water pipe that you mentioned.

Why would they have gone to the trouble of grounding the service panel in 1965 and then used ungrounded wires to run the circuits?
 
  #16  
Old 05-13-05, 08:09 AM
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"I just connect the new green ground wire to the white bus in the main fuse box and then replace the runner wire from the main box to the little one with a short piece of the same 220 wire I'll use to run the new dryer receptacle. Then they'll both be grounded. Excellent."

I'm not sure that I follow this. You should probably replace everything from the receptacle back to the panel. This means using 10-3 wire (which will be three insulated wires and a bare ground wire). I would not add a ground wire to a new receptacle and use the old wire. The old wire may not have a neutral, it may already have a ground.


Take a look at most of your electrical devices in your house. How many of them have a grounded plug and a need a three prong receptacle? I'll bet very few. It's generally only major appliances (washer, refrigerator, freezer, microwave) and computers. There are a few others, but not too many.

In 1965 there was generally no need for grounded circuits except for the few places they would be needed.

Today, there are computers, surge protectors, UPSs, as well as a plethora of other devices that need a good ground to function properly or to be safe.

As an aside, you can make an ungrounded receptacle safe for a three prong device by using a GFCI receptacle, but you cannot make it a properly functioning grounded receptacle in this manner.
 
  #17  
Old 05-13-05, 08:27 AM
mvigor
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To be more clear.... If I see that the fuse boxes are NOT grounded at all, I'll run a green grounding wire to a grounding rod outside, and connect it to the main box. If they were not grounded, then the short runner wire that connects the extension box to the main box will surely be without a bare wire inside so I'll have to replace that connection wire too.

Then, when I have a good ground in both of the fuse boxes, I'll replace the wire from the fuse box to the receptacle, the receptacle itself, dryer plug and cord and on down to the dryer. I'll also remove any bonding strip connecting the dryer's chassis to neutral.
 
  #18  
Old 05-13-05, 08:56 AM
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Do not try to ground this yourself. What you propose is not up to code, and may be worse than no ground at all. Please bring in a professional to do this.
 
  #19  
Old 05-13-05, 09:02 AM
mvigor
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Ok thanks for your suggestions. I guess I'll head off to the library and peruse the wiring books.
 
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