Sizing conductors

[dogboy]

The 800% value for Instantaneouse circuit breaker typically refers to an adjustable circuit breaker (Motor Circuit Protector) (ie have a 50A breaker with an instantaneous adjustment of 300% - 1000% or so to allow for inrush current LRA). For the purposes of your problem, I believe you would be better off with the Inverse time breaker of 250% (250% x 28A = 70A breaker). Or a 50A breaker with an instantaneous trip setting of 400%; 400%x50=200A. assuming non energy effecient motor or 600% if motor is energy efficient)

Motor thermal protection - Looks good
Non-Fused Disconnect switch 35A is minimum, the industry standard sizes are 30A, 60A, 100A

The fuse size you referenced is correct, just make sure you show everything on your drawing (breaker at panel, fuse at motor, The inverse time breaker will cover the overcurrent and ground fault, the instantaneous breaker will require a fuse for short circuit).

These are things I don't know and has not been covered in my studies. I am pulling numbers out of the NEC. I looked at my numbers and thought any fuse or breaker set less than @168A will blow on start-up. I do realize the start-up Amps are only for less than a second, but haven't been taught the limits. I do know I can not run my coffee pot, microwave, and toaster at the same time on a 15A breaker, it tripps. Yes, I know I need to run a new line to the microwave, I change out the vent hood with a microwave. You know, wire was allready there.

 

[dogboy]

So, I have it like this:

FLC= 28A
LRC= 168A
Wire size #4AWG due to 250 foot run
Inverse time breaker= 70A
Thermal protection= 40A
Disconnect switch= 60A (located wthin 50 feet of the motor)

Is thermal protection and heaters the same thing?

 

[manuelparedes]

Sizing conductor for continuos load and voltage drop adjustment

Sizing conductor for continuos load and voltage drop adjustment

Based on NEC article 210.19 (1) General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Where
a branch circuit supplies continuous loads or any combination
of continuous and noncontinuous loads, the minimum
branch-circuit conductor size, before the application of any
adjustment or correction factors, shall have an allowable
ampacity not less than the noncontinuous load plus
125 percent of the continuous load. Is it the voltage drop considered an adjustment factor? For example: if I have an equipment with rated load of 16A@120V, which is going to be ON for more than three hours (continuos load 16x1.25=20Amps@120VAC), and it is at 300 FT from the branch panel, do I have to use 16A or 20Amps for sizing the cable further due to the voltage drop? Please advise