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Old 12-23-2010, 07:26 AM   #1
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3 wire to 4 wire


I am upgrading to be current with code. My dryer has a three wire (prong) recepticle. I have been told current code is 4 prong. Advised to run fourth wire to the "neutral bus" on my panel. Maybe I'm missing something but I only see a bus for ground wire. Any idea about this??

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Old 12-23-2010, 07:38 AM   #2
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3 wire to 4 wire


In your main panel. your neutral bus and ground bus are on the same bar. Do you see ground (bare copper) and neutral (white) wires on that bar?

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Old 12-23-2010, 07:55 AM   #3
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3 wire to 4 wire


You can't run a single wire to the neutral bus unless you have a conduit system. You must run a new cable with four wires.
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Old 12-23-2010, 07:56 AM   #4
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3 wire to 4 wire


Unless you are moving the dryer, the setup is code compliant.
You only need to worry about rewiring if the dryer is being relocated.

On a side note, you cannot just run a wire unless you have conduit.
You would need to replace the cable that is there.
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Old 12-23-2010, 07:57 AM   #5
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3 wire to 4 wire


I didn't even notice that he'd be running a 4th wire after the fact. I was assuming (incorrectly) that he would be running a new 4-wire cable (well, 3 + egc).
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Old 12-23-2010, 11:05 AM   #6
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3 wire to 4 wire


Here's his other thread about the dryer circuit, for reference: Re routing the dryer supply

drjay, all the advice you've gotten so far it right on; since you made changes to the dryer circuit, it needs to be brought up to current code. This means replacing the old 10-2 w/ground cable with 10/3 w/ground.

It really is a lot safer with a separate ground and neutral wire, because with the old 3-wire connection, a fault in the dryer could electrify the dryer without tripping a breaker. I don't know why the older code ever allowed 3-wire connections.
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Old 12-24-2010, 12:55 AM   #7
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3 wire to 4 wire


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It really is a lot safer with a separate ground and neutral wire, because with the old 3-wire connection, a fault in the dryer could electrify the dryer without tripping a breaker. I don't know why the older code ever allowed 3-wire connections.
Just an informational query. Why is this type of wiring grandfathered into new code? Is is more safe today than it was when first installed?

It makes no sense to me that folks are discouraged to change over to a 4-wire whether or not the appliance has been moved. If the 3-wire system is considered unsafe, it should be replaced, imo.
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Old 12-24-2010, 08:16 AM   #8
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3 wire to 4 wire


With only one dedicated device on the circuit the three wire setup is not unsafe.
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Old 12-24-2010, 08:37 AM   #9
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3 wire to 4 wire


Quote:
Originally Posted by sirsparksalot View Post
Just an informational query. Why is this type of wiring grandfathered into new code? Is is more safe today than it was when first installed?

It makes no sense to me that folks are discouraged to change over to a 4-wire whether or not the appliance has been moved. If the 3-wire system is considered unsafe, it should be replaced, imo.
It's not that it is unsafe, but codes have changed that disallow this type of circuit from being added too.
Just like a kitchen or bath remodel needs to be brought to modern codes when done.
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Old 12-24-2010, 11:36 AM   #10
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3 wire to 4 wire


[ drjay, all the advice you've gotten so far it right on; since you made changes to the dryer circuit, it needs to be brought up to current code. This means replacing the old 10-2 w/ground cable with 10/3 w/ground.

It really is a lot safer with a separate ground and neutral wire, because with the old 3-wire connection, a fault in the dryer could electrify the dryer without tripping a breaker. I don't know why the older code ever allowed 3-wire connections.[/quote]

Seems to be a difference of opinion in this thread regarding safety.

Does anybody know for sure about safety of three wire?? It would be a lot easier to just reroute the 3 wireto the new location as opposed to running new 4 wire from box to new location. However if it is really unsafe Ill go the extra step. I did not plan on just adding fourth wire If I go this route I will get 10/3 with ground. Again, safe or not??
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Old 12-24-2010, 11:53 AM   #11
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3 wire to 4 wire


Quote:
Originally Posted by sirsparksalot View Post
Just an informational query. Why is this type of wiring grandfathered into new code? Is is more safe today than it was when first installed?

It makes no sense to me that folks are discouraged to change over to a 4-wire whether or not the appliance has been moved. If the 3-wire system is considered unsafe, it should be replaced, imo.
That #10 ground wire only has to handle about 2 amps of current. What would happen if someone needed a new dryer and found out that they had to upgrade the wiring to four wire and that it would cost half again as much as the new dryer? As long as it's installed properly there isn't a safety or operational issue.
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Old 12-24-2010, 12:02 PM   #12
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3 wire to 4 wire


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That #10 ground wire only has to handle about 2 amps of current. What would happen if someone needed a new dryer and found out that they had to upgrade the wiring to four wire and that it would cost half again as much as the new dryer? As long as it's installed properly there isn't a safety or operational issue.
Thats my issue, Corsair. If I can reroute and be safe and as I understand it NOT be in violation I'd like to keep the $200 dollars.

BTW: In your opinion better aircraft: Corsair or Intruder?
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Old 12-24-2010, 12:11 PM   #13
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3 wire to 4 wire


The only safety issue with 3-wire dryer circuits is this: Since the neutral and ground are bonded, that means the shell of the dryer is connected to neutral. Ordinarily not much of a problem. But if something were to happen to the neutral/ground connection, such as a broken wire or loose connection, that's where things get interesting. 120v parts of the dryer, such as the timer and motor, need to return current on the neutral to function. If there isn't a solid neutral connection available, the current will be trying to return on any other available path. Since the shell of the machine is connected to the neutral, that means 120v potential on the shell of the dryer. If you then touched that shell while (for instance) standing on a bare concrete floor, you would be the return path for that current.

Being in series with a 120v circuit is not a pleasant experience, and potentially fatal.

So basically, if the circuit is wired properly, if the the receptacle, plug, and cord are in good condition, and if there's nothing wrong with the dryer, then yes, a 3-wire circuit is as safe as a 4-wire. The NEC simply started requiring 4-wire circuits to remove most of those "ifs"

That said, safety is only half the equation; legality is the other. The NEC is the law when it comes to electrical wiring. Extending or modifying an existing 3-wire circuit is generally illegal, and we always tell people how to do things legally. It's easy to run into trouble down the road when things aren't done up to code. Making insurance claims and selling your house are two things that come to mind that can get much more difficult when electrical work hasn't been done to code.

I got a little long-winded here. I'm not trying to bust chops or tell anyone what to do, I'm just trying to provide some facts so an informed decision can be made.
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Old 12-24-2010, 12:21 PM   #14
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3 wire to 4 wire


I'm not trying to bust chops either, just interested in knowledge.

You and others keep repeating the situation where a neutral comes loose, and getting a return path via ground to the chassis of the appliance. And that this can be fatal. I agree. But then, you say it's alright to leave it as is because it's grandfathered to the code, and that if wired properly (what's proper?) it is as safe as 4-wire. Pardon my ignorance, but this sounds contridictory.

My argument isn't with you guys, it's with the NEC, but obviously you understand it better thatn I do, so I only ask for opinions
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Old 12-24-2010, 12:33 PM   #15
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3 wire to 4 wire


I see what you're saying sirsparksalot, but it would be impossible to make everyone who has a three wire circuit replace that circuit with a four wire not to mention all the other changes made in the code. The code makers know this so they grandfather it. The four wire dryer circuit is just a better overall setup.

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