10 HP 460V 3 Phases motor

[bobby mercier]

Could i use 14 AWG cable with THHN Wire to connect a 10 HP 460V 3 Phases motor.

[ June 11, 2004, 04:01 PM: Message edited by: bobby mercier ]

 

[roger]

Re: 10 HP 460V 3 Phases motor

Yes.

Roger

 

[iwire]

Re: 10 HP 460V 3 Phases motor

Sure if the run is not to long, and the job specifications allow it.

[ June 11, 2004, 04:09 PM: Message edited by: iwire ]

 

[stew]

Re: 10 HP 460V 3 Phases motor

iwire 17.5 amps on a 14? hmmmm

 

[bphgravity]

Re: 10 HP 460V 3 Phases motor

Whats wrong with 17.5-amperes on #14 THHN? Its good for 20A at 75 degrees C?

 

[ryan_618]

Re: 10 HP 460V 3 Phases motor

14 is good for 20 amps at 60 degrees.

Remember that 240.4(D) doesn't aplly to motor circuits, which is validated through 240.4(G)

 

[stew]

Re: 10 HP 460V 3 Phases motor

I know what you are saying its just my huble opinion borne out by years of experience that even though the ampacity is ok it is very close. A circuit of any long distance would pose unacceptable voltage drop conditions in my opinion. I would go with 12 just for drill. that being said I shall
just fade away

[ June 11, 2004, 08:00 PM: Message edited by: stew ]

 

[bphgravity]

Re: 10 HP 460V 3 Phases motor

Well thats precisely why Bob stated "if the run is not too long" in his post? Ambient temperature, voltage drop, and terminal ratings always have to be considered but in general, the #14 is good for 20A. The full load current is really only 14A so overloading of the #14 is not likely.

I also prefer to oversize my conductors, but from the code standpoint, that is only a design issue.

 

[ryan_618]

Re: 10 HP 460V 3 Phases motor

We were talking about this last night in the class I was teaching. It's like I was saying there, it isn't requirement to use #14. If you don't want to use something because your not sleeping well at night...well, use something bigger!

[ June 11, 2004, 08:48 PM: Message edited by: ryan_618 ]

 

[roger]

Re: 10 HP 460V 3 Phases motor

In good design I would think 14 would be a sorry choice, in a pinch (say a condition where the conductors were already in place) it would be fine as far as a code compliant installation.

Roger

 

[iwire]

Re: 10 HP 460V 3 Phases motor

It is very unlikely I would use 14 unless as Roger said we had some unusual circumstances.

We generally save the 14 for fire power limited fire alarm conductors.

 

[jimwalker]

Re: 10 HP 460V 3 Phases motor

And that #14 could be fused at 30

 

[bphgravity]

Re: 10 HP 460V 3 Phases motor

It could be protected by a 125A Instantaneous Trip Breaker as well!!!

 

[tom baker]

Re: 10 HP 460V 3 Phases motor

Ryan 14 AWG would be allowed for the this application. Table 240.3 allows article 430 rules to be used, and 240.4 (G) allows Motor and motor-control circuit conductors in parts
430, Parts III, IV, V, VI, VII for the ampacity, which when you follow the rules allows 14 AWG.

 

[charlie]

Re: 10 HP 460V 3 Phases motor

Another caveat to take into consideration when using #14 is its ability to withstand faults if a large amount of fault current is available. #14 wire is only good for 1700 amperes for one cycle and #12 is only good for 2700 amperes. If a fault is close to the service equipment, the use of these conductor is suspect. This is the reason that some municipalities have disallowed #14 under any conditions. You might take a look at the chart at the bottom of page 74 in the Bussmann SPD.