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Old 12-05-2009, 06:11 PM   #1
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Dryer and A/C wired differently???


In the process of moving a few breakers around in my main panel I noticed that my dryer circuit and A/C circuit are wired slightly differently, wondering which way is correct? Each circuit is on it's own 30A 2 pole breaker, using 10-2 wire. The difference is that on the dryer circuit, the bare wire is tied to the neutral bus bar, but the bare wire on the A/C circuit is tied to the ground bus. Is one way correct or incorrect? I'm thinking it doesn't matter, because the ground and neutral are tied together in the panel, but just want to be sure. Thanks

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Old 12-05-2009, 06:29 PM   #2
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Dryer and A/C wired differently???


The fact that the grounds and neutrals tie to the same bars is irrelevant. Outside the main disconnect or panel, such as with these branch circuits, they must remain separate in all but the most specific installations. This is to prevent objectionable current flowing on exposed metallic parts.

Also, 10/2 NM cable is not, and was NEVER, legal for a 120/240v dryer circuit. You need an insulated NEUTRAL wire for this circuit when it is/was run with NM cable.
For quite a few years now a 3-wire circuit is not even allowed for a dryer circuit.

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Old 12-05-2009, 07:26 PM   #3
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Dryer and A/C wired differently???


Interesting. I built the house 5 years ago, and had a good friend of mine do wiring (he was an electrical inspector for the city of Detroit). It also passed a stringent inspection from the city.

What would be the correct way to wire this? 10-3 for both A/C and dryer?
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Old 12-05-2009, 07:31 PM   #4
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Dryer and A/C wired differently???


No, an A/C would typically be a straight 240v circuit which does not require a neutral.

Five years ago would also have required a four wire circuit and receptacle for a dryer. If yours is a three hole receptacle then it is not and was not complaint.
The code change disallowing three-wire dryer circuits and receptacles was removed well over five years ago.

It sounds VERY scary that your friend is who you say he is, yet he wired an electric dryer with 10/2NM cable 5 years ago.
If for some reason this comes up in conversation do not let him try to convince you it is OK. It is NOT.
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Old 12-05-2009, 07:54 PM   #5
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Dryer and A/C wired differently???


I was under the impression that 3 wire dryer connections were normal in the past ??

Found this from another site:

Quote:
I believe the change from three to four wires started with the 1996 NEC.
Quote:
Originally Posted by Speedy Petey View Post
Also, 10/2 NM cable is not, and was NEVER, legal for a 120/240v dryer circuit. You need an insulated NEUTRAL wire for this circuit when it is/was run with NM cable.
For quite a few years now a 3-wire circuit is not even allowed for a dryer circuit.
Ah, re-read what you posted - I see, bare ground does not work in the past for a 3 wire dryer connection
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Old 12-05-2009, 08:19 PM   #6
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Dryer and A/C wired differently???


Exactly.
The exception was when type SEU cable was used. In that case the braided bare conductor was a neutral, not a ground.
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Old 12-05-2009, 08:27 PM   #7
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Dryer and A/C wired differently???


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Originally Posted by Speedy Petey View Post
Five years ago would also have required a four wire circuit and receptacle for a dryer. If yours is a three hole receptacle then it is not and was not complaint.
The code change disallowing three-wire dryer circuits and receptacles was removed well over five years ago.
:
not trying to argue with ya petey but up here in MI, we run by our own timelines.


Michigan has not been consistent in adopting up each code cycle in a timely manner. We almost skipped one (can't remember which one) just a couple cycles ago because the next one was already out or very soon to be out. It would take a lot of searching to find the exact time the 4 wire requirement came in but it may have been ok at the time for 3 wire (I know, but still not legal with 10/2+g NM).



we just adopted the '08 THIS Dec 2 (like 3 days ago)

do you remember what code cycle the 4 wire came in? I'm curious to find out if it was legal then or not (obviously with the correct cable though)
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Old 12-05-2009, 08:32 PM   #8
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Dryer and A/C wired differently???


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....do you remember what code cycle the 4 wire came in? I'm curious to find out if it was legal then or not (obviously with the correct cable though)
3-wire dryer and range circuits for dual voltage appliances (120/240) were discontinued for all new installations in the 1996 edition of the Code.
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Old 12-05-2009, 08:43 PM   #9
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Dryer and A/C wired differently???


No problem Nap. I had considered that as even here in NY up until two years ago we were under the previous NYS Resi code which was based on the 1999 IRC/NEC.

The 1999 NEC did not have the exception allowing 3-wire range and dryer circuits. I believe this edition removed it. That or 1996.
I do believe the 1993 edition allowed it.

I am missing 1993 & 1996 in my library of NEC's.
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Old 12-05-2009, 08:44 PM   #10
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Dryer and A/C wired differently???


Thanks KB. I was reading .pdf's and looking for my books that whole time.
I didn't see your post.
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Old 12-05-2009, 09:07 PM   #11
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Dryer and A/C wired differently???


well, I cannot find a historical listing of when what code was adopted but since it left in the 96 code and the house was built 5 years ago, for it to be legal, MI would have to have observed 93 code until 2003 or 4. I know we are slow up he in MI but not that slow. I am pretty sure that was not the case.

so, your "electrician" friend in DEEEtroit is not an electrician and I would guess the reason it passed inspection is because he is an electrical inspector.

so, unless the AC needed 120 volt as well as 240 volt (so the neutral would be needed as well), you would use 10/2+ground for the AC and 10/3+ground for the dryer. IF you needed the neutral for the AC, you would use 10/3+ground.
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Old 12-05-2009, 09:17 PM   #12
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Dryer and A/C wired differently???


It's probably here some where but I didn't go looking for it yet. MY understanding is it was 1996. Probably in the changes for article 250

http://www.mikeholt.com/technical.ph...%20-%20Summary
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Old 12-05-2009, 09:18 PM   #13
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Dryer and A/C wired differently???


Even though the cable in question is a three wire cable, it sounds like NM cable, which it was never okay to use the bare EGC for a neutral in a 120/240 volt circuit. SEU cable was OK prior to '96 if originating from the service equipment.

Even if the cable was SEU, it perhaps could still be in violation because the way I interpet the OP's explantation is the panel these circuits originate from could be a subpanel, with the service disconnect elsewhere. (He mentions ground and neutral bars seperately) I am not aware it was EVER okay to start a three wire 120/240 volt circuit like this from a subpanel. At least not in the timeframe of 5 years.
Quote:
The difference is that on the dryer circuit, the bare wire is tied to the neutral bus bar, but the bare wire on the A/C circuit is tied to the ground bus. Is one way correct or incorrect? I'm thinking it doesn't matter, because the ground and neutral are tied together in the panel, but just want to be sure.
Snowman, can you tell us if your panel is main or a sub? Also, you have a 4 prong cord and receptacle, or a three prong. Just curious. Thanks.
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Old 12-05-2009, 11:09 PM   #14
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Dryer and A/C wired differently???


It's a 3 prong outlet/cord, and main panel, not a sub. The only thing I can think of, is that I had the dryer already, and maybe he tried to re-use what I already had.

As far as my friend goes, he was a licensed electrician, working as an electrical inspector for Detroit. Unfortunately there will be no arguments with him about what is the correct wiring, he passed away 2 years ago from cancer at the age of 39. Thankfully, the IBEW took good care of everything.

I'm baffled if this wasn't done correctly though, everything else is done 150%, I told him to wire it as if it was his own house.
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Old 12-06-2009, 07:19 AM   #15
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Dryer and A/C wired differently???


Ouch. Sorry to hear that.

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