How To Connect 1/0 Aluminum To 70A Breaker? - Electrical - DIY Chatroom Home Improvement Forum


Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Display Modes
Old 10-09-2012, 05:49 PM   #1
Newbie
 
Join Date: Oct 2012
Posts: 2
Rewards Points: 10
Default

How to Connect 1/0 Aluminum to 70A Breaker?


How do you connect a 1/0 aluminum feeder cable to a Homeline - HOM270 breaker? The SPEC sheet for the HOM270 shows this breaker is designed for #8-2 AWG... so is there an adapter available that allows a 1/0 to connect to this breaker?

In case you're wondering... the reason I'm connecting a 1/0 to a 70 amp breaker is to compensate for the voltage drop which occurs on a 250 ft. feeder (between the service panel at the house) to the outbuilding sub-panel.

CMA = K x I x L x 2/7.2 = 21.2 x 70 x 250 x 2 / 7.2 = 103,056 CMA... and a 1/0 is 105,600... so this is the proper cable to get 70 amps to a sub-panel 250 feet away. I considered using copper, but due to budgeting issues, aluminum was the only realistic choice at this time.

Thanks for your help!

Advertisement

infoseek is offline   Reply With Quote
Old 10-09-2012, 06:44 PM   #2
Master Electrician
 
Join Date: Mar 2010
Location: Toronto Ontario
Posts: 1,165
Rewards Points: 500
Default

How to Connect 1/0 Aluminum to 70A Breaker?


Easy answer is that you don't connect it to that breaker.

Advertisement

__________________
Sarcasm is my friend
I'm here to learn too, i do mostly commercial/industrial/new construction and this place is a great way to pick up tips on residential from some good electrical minds. Excuse the spelling, my phone has a mind of it's own.
andrew79 is offline   Reply With Quote
Old 10-09-2012, 06:55 PM   #3
Semi-Pro Electro-Geek
 
Join Date: Jul 2009
Location: Arizona, USA
Posts: 2,569
Rewards Points: 2,034
Default

How to Connect 1/0 Aluminum to 70A Breaker?


You connect a smaller conductor to the breaker, and then use appropriate connectors (like split bolts) to transition to the larger conductor. You can do the transition inside the panel, so you only need a foot or so of smaller wire.
__________________
I am a lawyer, but not your lawyer. And who cares anyways? We're here to talk construction. This is DIY advice, not legal advice.
mpoulton is offline   Reply With Quote
Old 10-09-2012, 08:42 PM   #4
Newbie
 
Join Date: Oct 2012
Posts: 2
Rewards Points: 10
Default

How to Connect 1/0 Aluminum to 70A Breaker?


Think I may have figured out the problem... I was using 7.2 in my calculation because an electrician told me this is the number he always uses when calculating CMA. But upon reading an article online I see that Max Voltage Drop is dependent on the circuit voltage (which in my case is 240v) and the max allowable voltage drop (Ed) is 5%... which equals 12v for a 240v feeder circuit. Therefore by code I am allowed to use a 100A breaker on a 1/0 feeder circuit which is 250 feet in length.

CMA = K x I x L x 2 / Max Ed
21.2 x 100 x 250 x 2 / 12 = 88,333 CMA = 1/0

The problem (having to use a 70A breaker) is eliminated because a 100A breaker will accept wire from #4 to 2/0... and I have a 1/0 cable!

That is... unless I'm supposed to be taking 5% of 120v (6v) which changes everything.

So this Max Ed is truly the key.

Does anyone know if I'm supposed to take 5% of 120v or 5% of 240v?

Thanks for your feedback!
infoseek is offline   Reply With Quote
Old 10-09-2012, 08:46 PM   #5
Licensed Electrician
 
k_buz's Avatar
 
Join Date: Mar 2012
Location: SE Wisconsin
Posts: 4,343
Rewards Points: 2,006
Default

How to Connect 1/0 Aluminum to 70A Breaker?


There is no code in the NEC limiting voltage drop to less than any percent.
__________________
__________________________________________________ ______________
Answers based on the National Electric Code. Always check local amendments.


k_buz is offline   Reply With Quote
The Following User Says Thank You to k_buz For This Useful Post:
stickboy1375 (10-10-2012)
Old 10-09-2012, 11:11 PM   #6
UAW SKILLED TRADES
 
Stubbie's Avatar
 
Join Date: Jan 2007
Location: Kansas
Posts: 5,212
Rewards Points: 2,394
Default

How to Connect 1/0 Aluminum to 70A Breaker?


Quote:
Originally Posted by infoseek View Post
Think I may have figured out the problem... I was using 7.2 in my calculation because an electrician told me this is the number he always uses when calculating CMA. But upon reading an article online I see that Max Voltage Drop is dependent on the circuit voltage (which in my case is 240v) and the max allowable voltage drop (Ed) is 5%... which equals 12v for a 240v feeder circuit. Therefore by code I am allowed to use a 100A breaker on a 1/0 feeder circuit which is 250 feet in length.

CMA = K x I x L x 2 / Max Ed
21.2 x 100 x 250 x 2 / 12 = 88,333 CMA = 1/0

The problem (having to use a 70A breaker) is eliminated because a 100A breaker will accept wire from #4 to 2/0... and I have a 1/0 cable!

That is... unless I'm supposed to be taking 5% of 120v (6v) which changes everything.

So this Max Ed is truly the key.

Does anyone know if I'm supposed to take 5% of 120v or 5% of 240v?

Thanks for your feedback!
I admire your interest in learning the calculations ... it is beneficial to know how it is done .. BTW you use 240 volts not 120. Also there is much to know to provide a code compliant installation ... it is more than just running the correct size wire.

In the future try this ......

http://www.electrician2.com/calculat...alculator.html

Advertisement


Last edited by Stubbie; 10-09-2012 at 11:14 PM.
Stubbie 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
Added new breaker, no garage lights now. lum1nes Electrical 8 08-04-2012 08:50 PM
breaker keeps tripping RMCarner Electrical 29 07-22-2012 10:53 AM
Separate 110 and 220 receptacles on 2-pole 220 V Square D GFI breaker sunrise Electrical 1 05-13-2012 08:27 PM
Wiring Size Calculations for New Service CorinthWest Electrical 7 12-07-2010 12:36 PM
Circuit breaker panel - Advice needed justtired Electrical 15 12-13-2007 06:55 AM




Top of Page | View New Posts