Motor wires and disconnect

[Jpflex]

I’m installing a 3 phase 480 Volt, 5 HP motor




To determine SOOW cord wire size input to the motor:

I determined the FLA for the motor is 7.6 amperes according to NEC table 430.250

I then took 1.25 percent x 7.6 amperes to ensure the selected SOOW cord would be sized proper
= size wire capable of 9.5 amperes

NEC table 400.5 (A) 1 indicates selecting a 16 AWG or higher SOOW cord

However, I do not see any tables for ampere ambient temperature adjustment as you would with THHN. Conductors are not more than 3. Are you required to adjust ampacity for ambient temperature for cord? Our location has a design temp of 100 degrees free height according to copper.org

Normally I would derate THHN ampacity with starting insulation temperature rating of 90 degrees celcius to 0.91 percent for this ambient temp correction. However, I don’t know how this is to be done with jackets SOOW cord?


NOTOR DISCONNECT: 430.109


Lastly I’m trying to figure out a proper sized disconnect within 50 ft of motor

At company scrap piles, I found a disconnect rated at 575 volts which is overkill to applied 480v, 15 hp rated with fuses at 30 amperes (motor controller VFD overcurrent protection and overload already supplied upstream and selected by engineer previously)

I am not sure how to select disconnect interrupting current or if I need to know motor locked current with FLC? Do I need to verify this on selection? Thanks

 

[don_resqcapt19]

400.5(A) references the ampacity correction table in Article 310.

400.5(A) ... Where cords and cables are used in ambient temperatures other than 30°C (86°F), the temperature correction factors from Table 310.15(B)(1)(1) that correspond to the temperature rating of the cord or cable shall be applied to the ampacity in Table 400.5(A)(1) and Table 400.5(A)(2). Cords and cables rated 105°C shall use correction factors in the 90°C column of Table 310.15(B)(1)(1) for temperature correction.

You will have to find the actual temperature rating of the cord you are using as the product standard permits multiple temperature ratings to be used in the manufacture of the cord.
The following are the temperature ratings permitted by the product standard as found in the UL Guide Information for Flexible Cord (ZJCZ)

Types C, PD, SP-1, SP-2, SP-3, NISP-1, NISP-2, SRD, E, EO, ETP, ETT, TPT, TST and "Shaver Cord" are rated 60°C.
Types XTW and CXTW are rated 105°C.
Types SPE-1, SPE-2, SPE-3, SVE, SVEO, SVEOO, SJE, SJEO, SJEOO, SJEW, SJEOW, SJEOOW, SE, SEO, SEOO, SEW, SEOW, SEOOW, NISPE-1, NISPE-2, SRDE, HPD, HPN, HSJ, HSJO, HSJOW, HSJOO and HSJOOW are rated 90 or 105°C.
"Clock Cord" is rated 60 or 105°C.
Types SV, SVO and SVOO are rated 60, 75 or 90°C.
Types S, SO, SOO, SOW, SOOW, SJ, SJO, SJOO, SJOW, SJOOW, SVT, SVTO, SVTOO, SJT, SJTO, SJTOO, SJTW, SJTOW, SJTOOW, ST, STO, STOO, STW, STOW, STOOW, NISPT-1, NISPT-2, SPT-1, SPT-1W, SPT-2, SPT-2W, SPT-3, and SRDT are rated 60, 75, 90 or 105°C.

As always you will have to look at the maximum temperature rating of the equipment that the conductors are connected to and you are limited but the ampacities found in Table 310.16 no matter what the ampacity of the conductor may be. With the conductors you are using that is not likely to be an issue, but the termination of those conductors on the equipment may be. The typical equipment is not suitable for the termination of finely stranded conductors as used in flexible cords.

See 430.109 and 430.110 for your motor disconnect.