23amps and 14gauge wire, only used in panel?

[augiedoggy]

Yep! This is just a friendly conversation about wire types and some sharing and learning of the NEC. I did look at NFPA 79 last night and it agreed with Jerz - 14awg = 15a, 12awg = 20a, 10awg = 30a, etc, without specifying any difference between THHN, MTW, or others that I dont recall off hand.

But - NFPA 79 is more about wiring practices within machine tool electrical panels. It assumes initial ampacities from NFPA 70 - NEC.

And I was just offering my experiences with machinery I service and the long term effects of the current on the wiring in some cases...

BTW I took a look at some of the wiring harnesses in my garage and most of the wiring for the heating elements is 12 gauge not 10 as I originally thought (which makes more sense). and the heat damage on those was mainly at the spade connectors so I believe poor connections cause things to heat up and it had nothing to do with the choice of wiring as I originally thought it could have.

 

[atoughram]

Wires carrying element power I would use #10.

It is completely legal and safe to use #12 SO cord for hooking up 25amp elements per NEC table 400.5(A) (Allowable Ampacities of flexible cords) as long as there are only two conductors are current carrying.

 

[Jerz]

References:
2011 NEC (NFPA70)
110.14 Electrical Connections
TABLE 310.15(B) (formerly Tale 310.16)
240.4(D) Protection of Conductors (Small Conductors)

 

[Jerz]

That's funny... my table shows 20A for #12...

Edit: OK... I see what you're saying on column "B"...)

 

[atoughram]

See the note below the table.

 

[ingchr1]

It is completely legal and safe to use #12 SO cord for hooking up 25amp elements per NEC table 400.5(A) (Allowable Ampacities of flexible cords) as long as there are only two conductors are current carrying.

Even if using type SO, I personally would still upsize to #10 to allow some additional margin.

 

[Jerz]

Even if using type SO, I personally would still upsize to #10 to allow some additional margin.

I agree... but it is a good point that #12/3 SO cord could be used for the 5500W heating elements at 240V I guess. I've got #10/3 STOW cord with 30amp cord and plugs... It would save a little money plus the #12 is easier to work with than the #10... so very interesting point in this particular application. My concern might be the fuse prematurely blowing with about 23 amps worth of load on it but...

 

[atoughram]

the 12/3 cord I have on a 5500W element doesn't get warmer than ambient on my system.

BUT

Each to their own - if 12/3 works well, 10/3 wont hurt anything more than your wallet.

 

[ingchr1]

BUT

Each to their own - if 12/3 works well, 10/3 wont hurt anything more than your wallet.

For peace of mind for added margin to the cables rating, I'd gladly spend a few extra bucks. Really, what are we talking here maybe 50 cents more per foot at most?

 

[atoughram]

For peace of mind for added margin to the cables rating, I'd gladly spend a few extra bucks. Really, what are we talking here maybe 50 cents more per foot at most?

Closer to a buck a foot - but whatever makes you comfortable. (Home Depot for instance is $0.80/ft more)

I'm absolutely certain that there is plenty of safety margin built into the ampacity tables already.

It's not worth arguing for me - it's black and white and in a code book.

 

[ingchr1]

It's not worth arguing for me - it's black and white and in a code book.

Who's arguing? I never said #12 SO was unacceptable, all I said was if it was my system I would build additional margin into it by using #10. And for me the extra minimal cost is not going to hurt my wallet.

EDIT: Code wise I do not think #12 SO (rated at 25A) is acceptable for a 23A load. The codes are going to require the wire to be rated 125% of the rated load. So in this case one would need a 30A rated cable.