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Really need 14awg for fractional HP motor runs?

Really need 14awg for fractional HP motor runs?

Really need 14awg for fractional HP motor runs?

(OP)
At my company, the issue of wire gauge has been bothering me for some time.  Our machines range from some that are 120v powered, a few dc drives (fractional HP) to others that are 230 or 480v supplied with VFDs but again all less than 1HP.  At issue is the apparent NFPA 79 rule that all motor ("power") circuits be no smaller than 14awg wire.  We have some very small motors including one 120v fractional that draws less than 0.25A that come with 20awg leads.  It seems ridiculout to run 14awg to these motors - but what is the REQUIREMENT?  There are some excpetions in NFPA 79 but all appear to require a (class 10 or 20) overload on motor loads in order to lower the wire size.  We're simply feeding 120v through a simple abc type or other basic fuse and then to these small motors.  I can't imagine that 14awg is really needed but I haven't found justification to reduce the size.  What are the rest of you doing?

RE: Really need 14awg for fractional HP motor runs?

Many in the electrical field regard 14 AWG as the minimum for power or control wiring.  The NEC has tables that list the ampacity for the conductor sizes.

RE: Really need 14awg for fractional HP motor runs?

If the motor is part of a larger machine, is controlled and powered by that machineries wiring and overload management system, and is listed or tested as a single piece of equipment, leads can be sized by,,, conventional engineering.  Workmanship standards are nearly non-existant though, it's really amazing just how much junk you can hide under a little UL label!  

That's why the motors themselves can have leads less than 14AWG.

If wiring to a device leaves the physical confines of that single piece of machinery ("appliance" for example), it must satisfy the requirements of electrical wiring within buildings and facilities.

A 15A circuit is the smallest branch circuit in those areas.  The results of a short or overloaded circuit to or within the appliance itself are of little concern to the "NEC" ,,, or the AHJ.  The potential results within the occupancy are the real concern.

This seems to somehow escape some building inspectors, although that situation seems to be improving.  If a "custom" machine is built, it often is not listed as an appliance.  - By listed I mean bearing the U.L. label, or some other NRTL or agency. - If a machine is not inspected and accepted for listing by a NRTL, it must be compliant with requirements for wiring within buildings or commercial occupancies.  In many (most?) states one such requirement is that wiring be executed by a licensed journeyman electrician.  Another is obtaining an electrical work permit.

Please let us all know how this works out for you! and don't forget FAQ731-376

RE: Really need 14awg for fractional HP motor runs?

You refer to NFPA 79 But electrical code is NFPA Article 70NEC says that if it is a cord and plug connected device ie: a single recptacle and the motor has a plug then the min awg is 20 in a commerical dwelling, if resifential its 15 awg. if the equipment is part of loarger machinary like HCBFLASH says then the machinary shoukd carry some listing like"UL" then basicaly anything goes for the wire gauge. I am an electrical inspector in a  industrial area we see a lot of this stuff. suffolk bureau of electrical inspectors inc.

RE: Really need 14awg for fractional HP motor runs?

Look at NFPA70 - 300.1(b), amongst other articles...

RE: Really need 14awg for fractional HP motor runs?

The smallest standard breaker for use in electrical panels in North America is 15 amps. The smallest copper building wire that can be safely protected by a 15 amp breaker is #14. Hence the rule that the minimum wire size for most lighting and power circuits is #14 copper.
respectfully

RE: Really need 14awg for fractional HP motor runs?

Scramode,

Quote:

But electrical code is NFPA Article 70NEC says that if it is a cord and plug connected device ie: a single recptacle and the motor has a plug then the min awg is 20 in a commerical dwelling, if resifential its 15 awg.
While some local codes specify the above, the NEC does not require 20 amp circuits for commerical.
Don

RE: Really need 14awg for fractional HP motor runs?

I'm confused, is there a misunderstanding here about the meaning of AWG and AMP or is it just me?
There also are different standards for permanently installed wiring (Minimum 14 AWG with a 15 AMP breaker) and motors connected with a flexible cord and a plug.
respectfully

RE: Really need 14awg for fractional HP motor runs?

AWG - American Wire Gauge, the measurement of the conductor size.  #14 AWG is 0.0641 inch diameter (1.62814 mm diameter with about 2.525 Ohms resistance per 1000-ft (8.282 Ohms per km).

Amp - Ampere, the measurement of electrical current flow.

RE: Really need 14awg for fractional HP motor runs?

Quote:
["Scramode (Electrical)      
26 Jan 07 15:01
You refer to NFPA 79 But electrical code is NFPA Article 70NEC says that if it is a cord and plug connected device ie: a single recptacle and the motor has a plug then the min awg is 20 in a commerical dwelling, if resifential its 15 awg]


Hmmmm, I'm wondering where in NFPA70 you got those AWG figures.  (I keep meaning to go ahead and buy the whole pkg with the CD-ROM and search capabilities)

As far as my own experience goes, I've never run across a cord and plug smaller than 18ga.,

,,,,but I can't say I cut a lot of 'em open just to see.....
winky smile

RE: Really need 14awg for fractional HP motor runs?

sorry folks bad typing I ment 12 awg conductors and 20 amp circuits

RE: Really need 14awg for fractional HP motor runs?

Quote (waross):

The smallest standard breaker for use in electrical panels in North America is 15 amps. ...

Just as a minor aside, there are 10A breakers available for most major brands of panelboards and load centers. In addition for industrial applications here in North America, some of the IEC style "mini-breakers" that have heretofore been listed only under UL1077 as "supplementary circuit protectors" (that required another CB upstream), are now available in UL489 versions, which means they are fully capable of being used stand-alone to feed external devices and provide protection down to fractions of an amp.

That said, I don't think that makes any difference to the NEC requirements for minimum conductor sizing.

RE: Really need 14awg for fractional HP motor runs?

After changing awg to amp, there is still disagreement between Scramode and resqcapt19. Anyone care to cite an NEC article in his defense?

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