Fill in flow charts for motors & dwelling load cals.

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s wayne cook

Member
Location
Virginia
I'm in need of a printable, blank, fill in chart for figuring all the various calulations involved with motors, (such as FLA, OCP, Conductors, etc.) Preferably one that has the NEC Art. referenced.

The one I have is from the 87 NEC, And yes I know I'm getting old.

I've begun teaching on the Community College level, (principally the NEC), and I need all the helpful study guides I can get to share with my students.

I need the same type of chart for dwelling load calculations. I can't seem to download the information that Mike Holt makes available for free. Probably just my pitiful computor skills, but in any event, I just can't seem to obtain what I need.

Any and all assistance that can be provided is greatly appreciated.

Wayne Cook
 
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peter

Senior Member
Location
San Diego
Re: Fill in flow charts for motors & dwelling load cals.

This is a garbeled version of my Motor Calculation notes.
For each motor, you should have the following information:
1) Motor horsepower
2)Nameplate Amps [if none, use FLA] [Table 430-147-50]
3) Nameplate Volts
4) Phase [1 or 3][or 2?]
5) Service factor [IF=>1.15 THEN 1.25, ELSE 1.15]
6) Temp. Rise [IF <40?C, THEN 1.25]
7) Fuse or Circuit breaker?
8) 60? or 75??

Step 1-- Find Motor FLC [Tables 147-50]
Step 2-- Branch Circuit Conductors-- =FLC X 1.25 [Table 310-16]
Step 3-- Overload-- Nameplate Amps X 1.25 or 1.15 [Next Lower]
Step 4-- Branch Circuit Protection-- [Table 430-152] X FLC [Next Up]
Step 5-- Feeder Conductor-- (FLC of biggest motor X 1.25) + FLC Motor #2 + FLC Motor #3...
Step 6-- Feeder Protection-- Largest Branch Circuit Protection [step #4] + SUM of the rest of the FLCs [Step #1] [Next Down]

Then, if you want, you calculate the conduit sizes, derating and all that.

NOTE: I do not guarantee that this is correct. This is only a starting point for further refinement and any corrections or comments would be welcome.

~Peter
 
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