# Sizing breakers ?



## Jack30802 (Jul 6, 2013)

I just would like to get some input on how you size 
Breakers 3 phase 480 I can't really find a lot on it I like to size breakers on the size of the wire and set the overload per motor,specs is there a code or anything to say its has to be one way or another?


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## gold (Feb 15, 2008)

Your electrician will do that for you.


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## ponyboy (Nov 18, 2012)

These guys are coming out of the woodwork lately. Btl


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## Wirenuting (Sep 12, 2010)

Jack30802 said:


> I just would like to get some input on how you size
> Breakers 3 phase 480 I can't really find a lot on it I like to size breakers on the size of the wire and set the overload per motor,specs is there a code or anything to say its has to be one way or another?


We size them correctly. 
Sizing for motor loads is in the code book. 
Look thru the MH site, he just sent a newsletter about that topic. 

Other then that, let your electrician do the installs. No offense about you being a millwright, but rumor around the shop is that you guys can't make a good cup of coffee....


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## Jack30802 (Jul 6, 2013)

Loll you guys are ruff I'm starting to realize this might not be the right place for me


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## Wirenuting (Sep 12, 2010)

Jack30802 said:


> Loll you guys are ruff I'm starting to realize this might not be the right place for me


Sure, leave us flat. 
It ain't no fun picking on all our usual suspects. LoL


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## Wirenuting (Sep 12, 2010)

Wait,,.. Don't leave until you watch this YouTube Electrician ver Millwright vid. 
That's a great one.

http://youtu.be/2Kn-XXNCG8o

sorry for the bad link, I would screw up a wet dream given a chance.


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## LATTC (Feb 12, 2012)

We should not blame him; it's the cheap bastards that hired him.


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## Wirenuting (Sep 12, 2010)

LATTC said:


> We should not blame him; it's the cheap bastards that hired him.


So true,, LoL,
I sent him a couple of PM's with links to info. 
He seems like a nice guy and might stick around.


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## Jack30802 (Jul 6, 2013)

Lol yal guys are crazy I'm just trying to explore the options try to better myself tired of coming home dirty as crap every day I do a lot of traveling millwright work in papermills and coal mines and just like the way they have it set up with electrical and mechanical separate


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## Wirenuting (Sep 12, 2010)

Jack30802 said:


> Lol yal guys are crazy


Crazy?
That's article 517,,,, its were we are told how to install tamper proof stuff so they can't eat the trim screws. 
And yes, psych ward visitors do eat trim screws.


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## walkerj (May 13, 2007)

Wirenuting said:


> We size them correctly.
> Sizing for motor loads is in the code book.
> Look thru the MH site, he just sent a newsletter about that topic.
> 
> Other then that, let your electrician do the installs. No offense about you being a millwright, but rumor around the shop is that you guys can't make a good cup of coffee....


I thought millwrights were the epitome of a tradesman???


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## Wirenuting (Sep 12, 2010)

walkerj said:


> I thought millwrights were the epitome of a tradesman???


"Epitome"??? Man that's a big word. I'll look that up tomorrow. I don't want no nightmares tonight.


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## micromind (Aug 11, 2007)

The code doesn't specify a minimum breaker or fuse size, only maximum. 

Generally speaking, for a 480 3ø motor, I use a breaker or time-delay fuse that is double the HP of the motor. If it's 10HP, I use 20 amp. If it's 40HP, I use an 80. If the motor drives something that starts hard, I'll go up a size from double. 

Code-wise, you can almost always go up a couple of sizes from what I use, but in all the motors I've connected, I've yet to have an issue with doubling the HP. 

Wire size is 1.25 X the current listed in table 430.250, not the nameplate current. Use the 75º column in table 310.16. 

Overloads in starters are always based on the nameplate current, never the tables.


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## Jlarson (Jun 28, 2009)

There's an app for that. Get your smart phone thing and get er done.



walkerj said:


> I thought millwrights were the epitome of a tradesman???


I let ours play with the electricity. I figure what the hell.


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## Wirenuting (Sep 12, 2010)

Jlarson said:


> There's an app for that. Get your smart phone thing and get er done.
> 
> I let ours play with the electricity. I figure what the hell.


I sent him a PM last night and told him about the apps and gave him some links to motor and start circuits.


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## Introyble (Jul 10, 2010)

micromind said:


> Generally speaking, for a 480 3ø motor, I use a breaker or time-delay fuse that is double the HP of the motor. If it's 10HP, I use 20 amp. If it's 40HP, I use an 80. If the motor drives something that starts hard, I'll go up a size from double.
> 
> .



Guess you could say read 430.52 About your general dual element statement I think you should of warned the OP about the letter codes.

I ran into a 2 HP 480 3ø motor which has a 7.0 FLA arty:

Cool enough, except before I showed up I stop and purchased a starter and heaters. I approx the heater size and showed up with 2.7 - 3. whatever it was.


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## John Valdes (May 17, 2007)

Table 430.52


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