Breaker and wire size help - Page 2 - Electrician Talk - Professional Electrical Contractors Forum
CLICK HERE AND JOIN OUR COMMUNITY TODAY, IT'S FREE!
Go Back   Electrician Talk - Professional Electrical Contractors Forum > Electrical Trade Topics > Commercial Electrical Forum


Like Tree33Likes
Reply
 
Thread Tools Display Modes
Old 12-08-2018, 09:28 PM   #21
Senior Member
 
Join Date: Sep 2010
Location: Wisconsin
Posts: 546
Rewards Points: 84
Default

Quote:
Originally Posted by 847Videos View Post
He has the nameplate info available
I agree with everything else



Sent from my iPad using Tapatalk
The nameplate amps is only used for sizing overloads. Use the tables for wire size and overcurrent protection.
Mulder is offline   Reply With Quote
Join Contractor Talk

Join the #1 Electrician Forum Today - It's Totally Free!

ElectricianTalk.com - Are you a Professional Electrical Contractor? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's the leading place for electricians to meet online. No homeowners asking DIY questions. Just fellow tradesmen who enjoy talking about their business, their trade, and anything else that comes up. No matter what your specialty is you'll find that ElectricianTalk.com is a great community to join. Best of all it's totally free!

Join ElectricianTalk.com - Click Here JOIN FOR FREE


Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. ElectricianTalk.com DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

Sponsored Links
Advertisement
 
Old 12-08-2018, 09:34 PM   #22
Senior Member
 
847Videos's Avatar
 
Join Date: Dec 2014
Location: Illinois
Posts: 115
Rewards Points: 96
Default Breaker and wire size help

I would design the circuit for the specified load looking at the nameplate. Because thatís the load Iím trying to serve.
But common sense says, design the circuit with whatever wonít cause it to burn and have us looking like a holes...

Maybe design it off the charts and pick the better of the two.... The NEC is meant to be minimal standards... Therefore I agree with you.

#8 or #6
Iíd go with a #6 for better heat dissipation
Overload values off the name plate, because the goal/interest here is to protect the motor.

Breaker is short ckt protection for the feeders, and able to take the lock rotor amps at start up...

Grounding is very important on motors as well as the unit vibrates and if anything gets wacky, we want the breaker to trip.

Still think, compressors should be 3 phase if the property has it


Sent from my iPad using Tapatalk

Last edited by 847Videos; 12-08-2018 at 09:36 PM.
847Videos is offline   Reply With Quote
Old 12-08-2018, 09:42 PM   #23
Cow
Senior Member
 
Join Date: Jan 2008
Location: Eastern Oregon
Posts: 2,848
Rewards Points: 4,532
Default

Read 430.6(A)1 in regards to wire and breaker sizing.
Switched likes this.
Cow is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 12-08-2018, 09:53 PM   #24
Senior Member
 
WronGun's Avatar
 
Join Date: Oct 2013
Location: USA
Posts: 1,957
Rewards Points: 646
Default Breaker and wire size help

After reading the article and other posts on this subject Iíve found a dozen different answers....


Sent from my iPhone using Tapatalk
WronGun is offline   Reply With Quote
Old 12-08-2018, 09:54 PM   #25
Senior Member
 
847Videos's Avatar
 
Join Date: Dec 2014
Location: Illinois
Posts: 115
Rewards Points: 96
Default

Quote:
Originally Posted by Cow View Post
Read 430.6(A)1 in regards to wire and breaker sizing.

Respect where respect is due...
1,000% Correct.
Exactly how this is done.
And just for that, I'm going to revisit Article 430 myself as it never hurts to invest in our trade.
"Other than for motors built for low speeds (less than 1200 RPM) or high torques, and for mul- tispeed motors, the values given in Table 430.247, Table 430.248, Table 430.249, and Table 430.250 shall be used to determine the ampacity of conductors or ampere ratings of switches, branch-circuit short-circuit and ground-fault pro- tection, instead of the actual current rating marked on the motor nameplate."
847Videos is offline   Reply With Quote
Old 12-08-2018, 09:55 PM   #26
Senior Member
 
Switched's Avatar
 
Join Date: Dec 2012
Location: California
Posts: 6,064
Rewards Points: 8,856
Default

Quote:
Originally Posted by WronGun View Post
After reading the article and other posts on this subject Iíve found a dozen different answers....


Sent from my iPhone using Tapatalk
This is a confusing section for those of us that don't work with it everyday. I don't quite understand all of it either, but the explanations here make sense.
Switched is online now   Reply With Quote
Old 12-08-2018, 09:56 PM   #27
Senior Member
 
847Videos's Avatar
 
Join Date: Dec 2014
Location: Illinois
Posts: 115
Rewards Points: 96
Default

Quote:
Originally Posted by WronGun View Post
After reading the article and other posts on this subject Iíve found a dozen different answers....

Read the code, everything else is just an opinion...
Back it up your design with article numbers
847Videos is offline   Reply With Quote
Old 12-08-2018, 09:58 PM   #28
Senior Member
 
cabletie's Avatar
 
Join Date: Feb 2011
Location: N.J.
Posts: 1,698
Rewards Points: 1,274
Default

Nope only one answer. Cowís is correct.
HackWork and 847Videos like this.
cabletie is offline   Reply With Quote
Old 12-08-2018, 09:59 PM   #29
Senior Member
 
847Videos's Avatar
 
Join Date: Dec 2014
Location: Illinois
Posts: 115
Rewards Points: 96
Default

Quote:
Originally Posted by cabletie View Post
Nope only one answer. Cowís is correct.



I second that, Cow is correct.
Verify with the article numbers he provided
847Videos is offline   Reply With Quote
Old 12-08-2018, 10:00 PM   #30
Senior Member
 
Switched's Avatar
 
Join Date: Dec 2012
Location: California
Posts: 6,064
Rewards Points: 8,856
Default

So... Can I go back and edit my incorrect post? lol
847Videos likes this.
Switched is online now   Reply With Quote
Old 12-08-2018, 10:00 PM   #31
Senior Member
 
WronGun's Avatar
 
Join Date: Oct 2013
Location: USA
Posts: 1,957
Rewards Points: 646
Default

Quote:
Originally Posted by 847Videos View Post
Read the code, everything else is just an opinion...
Back it up your design with article numbers


Sure #6 on a 60 would work , but it seems #8 on a 50 would Also be acceptable.

Yes itís true I donít work on this Everyday , the nameplates Iíve used for installations in the past offered more information. Min and max breaker size , fla, etc.etc. Iíve never had to dig very deep.


Sent from my iPhone using Tapatalk
WronGun is offline   Reply With Quote
Old 12-08-2018, 10:03 PM   #32
Senior Member
 
847Videos's Avatar
 
Join Date: Dec 2014
Location: Illinois
Posts: 115
Rewards Points: 96
Default

Quote:
Originally Posted by WronGun View Post
Sure #6 on a 60 would work , but it seems #8 on a 50 would Also be acceptable.

Yes itís true I donít work on this Everyday , the nameplates Iíve used for installations in the past offered more information. Min and max breaker size , fla, etc.etc. Iíve never had to dig very deep.


Sent from my iPhone using Tapatalk

I've always used Name Plate
I have a digital copy of the code book
And from now on, I'll bring it up on my phone and design the everything except the heaters off the charts just like the code specifies....


Good time we bust out and knock the dust off our code books hu... lol
847Videos is offline   Reply With Quote
Old 12-08-2018, 10:04 PM   #33
Senior Member
 
Switched's Avatar
 
Join Date: Dec 2012
Location: California
Posts: 6,064
Rewards Points: 8,856
Default

Quote:
Originally Posted by WronGun View Post
Sure #6 on a 60 would work , but it seems #8 on a 50 would Also be acceptable.

Yes itís true I donít work on this Everyday , the nameplates Iíve used for installations in the past offered more information. Min and max breaker size , fla, etc.etc. Iíve never had to dig very deep.


Sent from my iPhone using Tapatalk
I thought 8 on a 50 would work, because I incorrectly thought we could use the nameplate FLA to size the breaker. The section @Cow mentioned though shows I was wrong.
847Videos likes this.
Switched is online now   Reply With Quote
Old 12-08-2018, 10:14 PM   #34
Senior Member
 
cabletie's Avatar
 
Join Date: Feb 2011
Location: N.J.
Posts: 1,698
Rewards Points: 1,274
Default

Iím glad I wasnít the first one in. I didnít have the time to respond when I first read it. When I did the math on a calculator I came up with #8 on a 100amp breaker. But I used 230 volts. You canít see the tables when your using an app like ElectriCalc

When I saw Cowís response I opened up the table to see the different columns. I though 230v covered it down to 208v.
cabletie is offline   Reply With Quote
Old 12-08-2018, 10:16 PM   #35
Senior Member
 
WronGun's Avatar
 
Join Date: Oct 2013
Location: USA
Posts: 1,957
Rewards Points: 646
Default Breaker and wire size help

Well this has been a great lesson on motors...

Good news is I can use the existing 3/4Ē emt

Sent from my iPhone using Tapatalk
WronGun is offline   Reply With Quote
Old 12-08-2018, 10:19 PM   #36
Modťrateur
 
frenchelectrican's Avatar
 
Join Date: Mar 2007
Location: Philippines
Posts: 8,634
Rewards Points: 16,780
Default

Quote:
Originally Posted by WronGun View Post
Well this has been a great lesson on motors...

Good news is I can use the existing 3/4Ē emt

Sent from my iPhone using Tapatalk
It is and you will run into central air conditing system ., same way with motors as you will review art 430 and art 440 from time to time to remind yourself on the numbers.
__________________
Bleu est beau.
frenchelectrican is offline   Reply With Quote
Old 12-08-2018, 10:22 PM   #37
Senior Member
 
WronGun's Avatar
 
Join Date: Oct 2013
Location: USA
Posts: 1,957
Rewards Points: 646
Default

Quote:
Originally Posted by frenchelectrican View Post
It is and you will run into central air conditing system ., same way with motors as you will review art 430 and art 440 from time to time to remind yourself on the numbers.


Im sure i will.

The last few rtuís i did had everything laid out the on plate including conductor sizes.


Sent from my iPhone using Tapatalk
frenchelectrican likes this.
WronGun is offline   Reply With Quote
Old 12-09-2018, 06:58 AM   #38
Hackenschmidt
 
splatz's Avatar
 
Join Date: May 2015
Location: Parts Unknown
Posts: 8,163
Rewards Points: 3,720
Default

Correct me if I am wrong, here is how I figure...

The HP field is 7.5, simple enough. The AMPS field on this nameplate is 31, that's the FLA, but that's not the FLC. Already confusing.

FLC is not found on the nameplate, you find the FLC for the HP in the table. (In this case, 430.28 for single phase AC motors.) The tables account for power factor and efficiency.

Wire size for CCC's is based on the FLC. (If the load is continuous, the 80% rule / 1.25 multiplier applies as usual.)

The OCPD size can exceed the usual max, the max OCPD allowed is calculated from FLC and a multiplier from 430.52. The lookup in 430.52 depends on the type of motor. (I am not clear other than consulting the manufacturer how you walk up to a motor and know which type it is.)

Overloads may be built into the starter or dual element fuses in the disconnect. Overloads are sized from FLA and a multiplier per 430.32. For motors > 1hp, the multiplier is

* 1.25 for motors with SF > 1.15, OR, temperature rise 40įC or less
* 1.15 otherwise

SF is clearly marked on the nameplate, not sure about temperature rise.

To NEMA and NEC, it would be super, super helpful if you f***ing f***s could use the EXACT SAME TERMS AND LABELS.
__________________
Everything Should Be Made as Simple as Possible, But Not Simpler

Last edited by splatz; 12-09-2018 at 07:28 AM.
splatz is online now   Reply With Quote
Old 12-09-2018, 07:03 AM   #39
Senior Member
 
HackWork's Avatar
 
Join Date: Oct 2009
Location: -
Posts: 32,639
Rewards Points: 421
Default

I am glad that some of you got it, because I don't have a clue what is going on.
HackWork is online now   Reply With Quote
Old 12-09-2018, 07:22 AM   #40
Senior Member
 
WronGun's Avatar
 
Join Date: Oct 2013
Location: USA
Posts: 1,957
Rewards Points: 646
Default

Ok ... I feel a little better now knowing my head isnít the only one that is spinning.


Sent from my iPhone using Tapatalk
WronGun is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Is this Electrician correct on wire sizing? grover1134 General Electrical Discussion 10 11-05-2018 07:15 PM
Heating Loads and Wire Size darren79 Canadian Electrical Forum 2 01-20-2017 07:33 PM
60 amp double pull breaker on 12, 14 gauge wire. Gamble Residential Electrical Forum 7 09-24-2016 05:35 PM
Is this overkill? MTW NEC Code Forum 81 03-20-2016 09:26 PM
Help with this a/c breaker sizing TechieBecky Canadian Electrical Forum 73 02-27-2016 06:26 PM


All times are GMT -4. The time now is 09:55 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Our Pro Sites Network
ContractorTalk.com | DrywallTalk.com | HVACSite.com | PaintTalk.com | PlumbingZone.com | RoofingTalk.com