4 wire 220v outlet to 3wire

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  #1  
Old 12-04-05, 07:35 AM
gyyr
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4 wire 220v outlet to 3wire

I just moved into a new house with a 4 hole outlet for the dryer, but our dryer has a 3 prong pigtale. Is it ok to either wirenut the ground and netural together or just leave the ground wire disconnected? The grounds and neutrals are bonded together in the breaker boxl. Thanks
Robert
 
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  #2  
Old 12-04-05, 08:01 AM
Speedy Petey's Avatar
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ABSOLUTELY NOT!

You must replace the pigtail with a 4-wire. The receptacle in the house MUST remain a 4-wire.
This is by far the easier way to go anyway.
 
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Old 12-04-05, 08:27 AM
gyyr
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If the ground and neutral are bonded together in the breaker box, I dont understand why connecting them in the box would not work. Would another alternative be to connect the 3 hole outlet and then connect the the ground from the plug to the grounding screw on the back of the dryer? Thanks for your help.
 
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Old 12-04-05, 08:50 AM
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No. The ONLY alternative is to replace the cord set. The receptacle MUST remain a 4-wire.

If the ground and neutral are bonded together in the breaker box, I dont understand why connecting them in the box would not work.

This logic is a very common misconception to a DIYer. The main panel/disconnect is the ONLY place the two are bonded. Everywhere else, with one exception, the grounds and neutral must remain isolated.
The reason is in depth and can be found on the web if you do the right search, but believe me about the facts.

Like I said, it's so much easier to just replace the cord anyway.
 
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Old 12-04-05, 08:51 AM
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Long story short

In older 220 volt clothes dryers that utilized a three-wire plug, two of the prongs were "hot"... each carrying 120 volts (nominal ), and the third was the "neutral", which also doubled as a grounding wire for the metallic body of the dryer. The neutral wire completes the electrical circuit back to the main electrical panel and then to the ground.

The latest electrical code requires a fourth prong on all 240 volt plugs. This additional plug is a separate ground for the appliance frame. The separate ground is a backup in the event the neutral wire becomes disconnected... for safety reasons, of course. Should one of the hot wires accidentally touch the body of the clothes dryer, the rush of electricity to the "ground" will cause the circuit breaker to trip and turn off the power. By having this additional wire leading to ground, there is less chance of the metal frame of the dryer becoming electrically charged... a possibly deadly situation!

Look at the power "block" where the prongs on the plug are attached. There is usually some sort of removable metal linkage that connects the neutral terminal to the body of the dryer. This "bridge" must be disconnected. Then, attach the new ground wire to the body of the dryer. Sometimes there is a screw at the end of the grounding linkage that allows this connection to be made. Or, you may have to drill a hole into the frame and attach the ground wire using a sheet metal screw and a washer.

Test the ground with a multimeter set to check resistance... touch one terminal to the body of the dryer (bare metal) and another to the ground prong on the plug... if you show positive resistance you have correctly grounded the appliance. If your meter doesn't show resistance, check to be sure your ground connection is onto bare metal. You may have to even scrape off a little paint to make a good connection.

But other than that a few more reasons I can go into the most important one is that the NFPA and NEC decided it was a safety hazzard to not have the direct path to ground in case of eneregized metal on the appliance...trust me it is for your safety...and the 4 wire extentions only cost about 8-15 bucks...
 
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Old 12-04-05, 09:20 AM
gyyr
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Thank you for the information. I am going to take your advice and buy a 4 prong pigtale. I do have one more question though. Hopefully I can explain this so you can understand. When I remove the access panel I see a terminal block with a place for only 3 wires. There is a screw on the outside of the dryer with a green wire connected to it labeled "external ground connector". When I follow that green wire back from the screw it is sodered to the neutral, before the neutral reaches the terminal block. The green wire is only about 3" long. Since these wires are sodered together, when I get the 4 wire pigtale, can I connect the ground and neutral to the same terminal or do I need to do something different. Thanks again for all your help.
 
  #7  
Old 12-04-05, 09:29 AM
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No. That ground wire must be removed and cut off or taped securely.

On the new cord set, B, W, and R go to thier corresponding colors on the terminals. The green goes to the green screw in the frame of the dryer.
 
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Old 12-04-05, 09:40 AM
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gyyr,

My man Speedy hooked you up on the correct answer. Just so you know doing what you stated would be no different than the question you had in your first post which is why you have to remove the connect of that green jumper wire to the neutral wire.

I will post again the procedure in detail:
Look at the power "block" where the prongs on the plug are attached. There is usually some sort of removable metal linkage that connects the neutral terminal to the body of the dryer. This "bridge" must be disconnected. Then, attach the new ground wire to the body of the dryer. Sometimes there is a screw at the end of the grounding linkage that allows this connection to be made. Or, you may have to drill a hole into the frame and attach the ground wire using a sheet metal screw and a washer.
Ok in the statement above the "bridge" is that green 3' wire you are refering to. You would then take the ground wire from the new 4 wire cord and take it to the green screw on the metal case...and as Speedy perfectly stated you need to unscrew the green wire from the metal case, cut off the end fitting ( if their is one ) and place a wirenut on it and wrap well with electrical tape.....and just to be safe wrap it good...lol
 
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Old 12-04-05, 09:49 AM
gyyr
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Thank you both for your helpful and quick responses. I am off to the store to get a new pigtale and some electrical tape.
 
  #10  
Old 12-04-05, 12:04 PM
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Originally Posted by ElectricalMan
The latest electrical code requires a fourth prong on all 240 volt plugs.
You do mean all new 240V dryer plugs, right? A non-electrician reading that would have thought you meant that dryers were involved because all 240V plugs were involved, which certainly isn't the case. I know you know, but I'm clarifying for the DIYers.
 
  #11  
Old 12-04-05, 04:31 PM
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All 120/240V recepticles.
 
  #12  
Old 12-27-05, 08:41 PM
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It is probably too late for the original poster... However, having moved from a house with a 4-prong dryer outlet to a house with a 3-prong dryer outlet, I would recommend trying to make these modifications "undoable" and avoid "cutting off the green ground wire".

My dryer's manufacturer directions say that when the dryer is used with a 4-prong plug, the green ground wire (that connects the neutral to the metal case) is to be unscrewed from the green grounding screw in the metal case and attached to the same screw as the neutral wire from the plug. This effectively makes the short grounding wire a "loop to nowhere".

If you ever move to another house that doesn't have a 4-prong outlet, you'll need to put back on your old 3-prong plug (or a new one). If you cut off the wire, you'll either need to replace it or you will have to replace the 3-prong outlet with a 4-prong one.
 
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