wire: 10-2 or 10-3 ?

cartunes · Nov 11, 2009

Question about when to use 10-2 or 10-3.
For my 240v welder circuit I planned to use 10-2 wire with a 50amp breaker. The welder plug has 3 prongs, so I assume 10-2 is correct. Or is it?

Same question about the 240v lift circuit.

My 240v compressor was previously connected with 12-2.

Thanks, Ron

Mr_fixit · Nov 11, 2009

6-2 would be correct for a 50 amp breaker. 10-2 would be for 30 amps. A welder usually has a 50 amp plug. ( even though the actual cord on some machines might only be 12-2. ... which confuses the hell out of me.

12-2 would be right usually for a air compressor, since most of them are less than 20 amps.

cartunes · Nov 11, 2009

My understanding is that a 50a welder circuit can use 10ga wire because of the short duty cycle. Whereas a 50a circuit for say a large electric space heater would need the heavier wire. But I'm not an electrician

So when do you use 10-3 (or **-3) for anything? For multi-phases?

jkeyser14 · Nov 11, 2009

cartunes said:
My understanding is that a 50a welder circuit can use 10ga wire because of the short duty cycle. Whereas a 50a circuit for say a large electric space heater would need the heavier wire. But I'm not an ellectrician

So when do you use 10-3 (or **-3) for anything? For multi-phases?

You use 10-3 when you have something that needs both 120v and 240v. 240 has the return current through the legs of wire, 120 has it through a neutral. In both instances you have a ground for safety.

Red Green · Nov 11, 2009

cartunes said:
My understanding is that a 50a welder circuit can use 10ga wire because of the short duty cycle. Whereas a 50a circuit for say a large electric space heater would need the heavier wire. But I'm not an electrician

So when do you use 10-3 (or **-3) for anything? For multi-phases?

For your welder what you want is 10-2 with a ground.

The 10-3 is mainly used for household ranges that have 4 prongs on the plug it also has a ground wire.

EDIT: I am not an electrician this is what I used and it has never been a problem. I looked today and I have a 30 amp breaker.

Nostraquedeo · Nov 12, 2009

Doesn't matter what the load is of the welder. If you put in a 50amp breaker, you need to put in the proper size wire(Rated for 50amps). The breaker protects the wire. If the wire is rated below the breaker trip rating, we wouldn't need breakers. As far as 10-3, you could use it for a range, where you have two phase wires and a neutral. The two phase wires would be your 240v for the heating element in the range, and the neutral along with a phase wire would be for your range electronic controls, requiring 120 volts.

sberry · Nov 12, 2009

You can use a 10 with 50A breaker depending on the machine connected to it.

Falcon67 · Nov 12, 2009

From a practical standpoint for a compressor, etc, you'd just use 10-3 because that's common in the stores and just ignore the neutral lead - clip it on the load end and terminate it in the panel just because.

snorky18 · Nov 12, 2009

Nostraquedeo said:
Doesn't matter what the load is of the welder. If you put in a 50amp breaker, you need to put in the proper size wire(Rated for 50amps). The breaker protects the wire. If the wire is rated below the breaker trip rating, we wouldn't need breakers.

That was my impression until I read all of the code and posts in this thread:
http://www.garagejournal.com/forum/showthread.php?t=46813
Summary: Apparently under some very specific circumstances, it appears that it is acceptable by code to install a breaker bigger than the capacity of the wire (such as putting 12 ga Romex on 30 Amp breaker for a dedicated compressor circuit), but it's all kinda confusing to me, and INAE (I'm not an electrician), so don't take my word for it.

One thing I do know is there is nothing WRONG with doing it your way, and over-sizing the wire, just costs more $ and is harder to work with, but is more conservative (safer). And for the non-electricians who don't have a very, very intricate knowledge of NEC, its no doubt a much better policy to follow. :thumbup:

IanF · Nov 12, 2009

sberry said:
You can use a 10 with 50A breaker depending on the machine connected to it.

A homeowner can do this... an electrician would lose his license... and I would get fired...

50A C.B. get's #6 AWG, maybe #8. There is some leeway when sizing wire for voltage drop per the NEC, but for circuit breakers, it's rather clear cut. Appendix B, 310 tables.

FastEddieG · Nov 12, 2009

IanF said:
A homeowner can do this... an electrician would lose his license... and I would get fired...

50A C.B. get's #6 AWG, maybe #8. There is some leeway when sizing wire for voltage drop per the NEC, but for circuit breakers, it's rather clear cut. Appendix B, 310 tables.

You would be interested in this thread then

Nostraquedeo · Nov 12, 2009

FastEddieG said:
You would be interested in this thread then

Despite any exceptions in the code for oversizing cb's for motor starting, it's just not safe practice to oversize the breaker and not provide adequate wire size. It's a recipe for wires burning and starting fires. No way would I ever design a circuit in that manner. I would maybe use the exception as a feild fix for nuisance tripping, but never as a new design.

walrus · Nov 12, 2009

Nostraquedeo said:
Despite any exceptions in the code for oversizing cb's for motor starting, it's just not safe practice to oversize the breaker and not provide adequate wire size. It's a recipe for wires burning and starting fires. No way would I ever design a circuit in that manner. I would maybe use the exception as a feild fix for nuisance tripping, but never as a new design.

How are the wires going to burn when the overloads on the motor are tripped at a level below the ampacity of the wires?

Aceman · Nov 12, 2009

Where do all these people come from?

None of them seem to be electricians, they don't know code, but they still manage to try and convince everyone on this forum that they know what's best.

Stick to giving advice about what you know instead of talking out your a$$ about what you don't.

djjsr · Nov 12, 2009

Well said Aceman. Some of the electrical advice I've read on this forum would burn your house down.

FastEddieG · Nov 13, 2009

I don't claim to be an electrician or to know (and understand) the code, but I'm curious for my own knowledge what is dangerous about using a wire size that correlates with the breaker size?
-Ed

GeorgiaHybrid · Nov 13, 2009

FastEddieG,

I'm not an electrician but do trust Charles, Aceman and a few others on this board. I try to listen, ask questions and learn somethings while on here. I did borrow a copy of the NEC and researched what I could (reads like lawyerese at times) and from what I found, you CAN use the smaller wire on certain DEDICATED circuits (just like they real electricians stated). You can also run a wire sized to the breaker but it is not required under the requirements in the code for those circuits.

Nostraquedeo · Nov 13, 2009

GeorgiaHybrid said:
FastEddieG,

I'm not an electrician but do trust Charles, Aceman and a few others on this board. I try to listen, ask questions and learn somethings while on here. I did borrow a copy of the NEC and researched what I could (reads like lawyerese at times) and from what I found, you CAN use the smaller wire on certain DEDICATED circuits (just like they real electricians stated). You can also run a wire sized to the breaker but it is not required under the requirements in the code for those circuits.

Remember, the code is a minimum requirement.

FastEddieG · Nov 13, 2009

GeorgiaHybrid said:
FastEddieG,

I'm not an electrician but do trust Charles, Aceman and a few others on this board. I try to listen, ask questions and learn somethings while on here. I did borrow a copy of the NEC and researched what I could (reads like lawyerese at times) and from what I found, you CAN use the smaller wire on certain DEDICATED circuits (just like they real electricians stated). You can also run a wire sized to the breaker but it is not required under the requirements in the code for those circuits.

Thanks for the reply, but that's not what I asked. I'm trying to ask questions and learn here too. I've seen people from 2 threads now that both offered their opinion of using thicker wire and were slammed as giving dangerous advice. I'm curious because logically that doesn't make sense to me. I can understand if the argument is you're overspending on wire that you don't need to, or something on the "overkill" side, but I can't understand the dangerous side.

So my question is, what is dangerous about running wire properly sized to the breaker instead of thinner bare minimum wire as stated by code for that application?

-Ed

IanF · Nov 13, 2009

FastEddieG said:
You would be interested in this thread then

That thread is so full of B.S. I won't even post there.

Now I remember why I stopped coming to this forum...

If you are on the freakin' internet asking for electrical advice: HIRE AN ELECTRICIAN.

walrus · Nov 13, 2009

FastEddieG said:
So my question is, what is dangerous about running wire properly sized to the breaker instead of thinner bare minimum wire as stated by code for that application?

-Ed

I'm not sure where anyone said it was dangerous. Folks were saying the downsized wire was dangerous, when in certain applications meets current code. I think the problem arises when guys who have done things one way(the way they were taught) think any other way doesn't meet code.

GeorgiaHybrid · Nov 13, 2009

FastEddie,

Read what I posted. The smaller wire is the MINIMUM allowed by code. I also stated that you can run a wire sized for the breaker. You can run a wire that is 128" in dia if you could buy one that big and protect it with a 15 amp breaker. The problem was that statements were made that you could not run a wire sized smaller than the breaker and THAT would be dangerous NOT that running a larger wire was dangerous.

That statement was incorrect and it has been pointed out several times by guys on this board who DO know the NEC codebook. If in doubt, hire a good electrician to wire it up for you.

mikeyr · Nov 16, 2009

I am not a electrician but I nearly always one size up my wire, 50 amp requires 6AWG and that is that, period. You don't know what you will use that plug for in the future, you might have some loophole that may be safe to use smaller wire but next owner will burn it down or you will in 10+ years when you get some new cool toy and forgot you used a loophole.

Look at it this way...a few dollars wasted on correct sized wire vs. a few hundred thousand wasted rebuilding your hour, proper wiring is cheap.

Nealcrenshaw · Nov 20, 2009

50 amps go AWG #6
The duty cycle of a compressor has absolutely nothing to do with wire size.
#10 is good up to 30 amps no more.

srmofo · Nov 20, 2009

All this stuff confuses me at times but I am getting ready to wire my new garage(with the help of an electrician neighbor). Is there just a table somewhere that explains what size wire to run for a a certain breaker? Id like to draw a plan up and have a little beatter understanding so I dont waste his time.

Im not interested in a loop holes or ways around spending money on more expensive wire. As previously stated what happens when someone doesnt know the wire isnt rated for what the breaker is. IMO its just not worth the risk to save a few bucks.

Also I have a brand new roll (250') of 10-3. where could I put it to good use? If nothing else maybe just a couple of good high amp recepticles? I dont want it sitting around for another 5 years. I have this compressor

http://www.homedepot.com/h_d1/N-5yc1vZ1xml/R-100005910/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

and plan on getting this welder soon.

http://www.millerwelds.com/products/tig/diversion_165/

I have several books on the subject I just havent had the time to sit down read and digest the material yet.

sorry for the thread jack I just didnt see a need to start a new one on the same subject

wire: 10-2 or 10-3 ?

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