Notices

my last ELECTRICAL question

Old 02-11-2014, 02:52 PM
  #1  
Senior MemberCaptains Club Member
Thread Starter
 
Join Date: Dec 2007
Posts: 15,745
Likes: 0
Received 653 Likes on 359 Posts
Default my last ELECTRICAL question

...for the month


The electrician that will do the final hookups told me to source cable for a 65A circuit breaker on our Generac 16Kw whole-house generator. I'm getting conflicting information on the internet, and around town. Here's hoping that a THT concensus will get the job done:

Total run is about 70' to the transfer switch from the genset. Install will be in PVC because it will go above and below ground.

? What size cable is correct?
? Any preference of copper over aluminum?

This is a Generac 16Kw with a 65A circuit breaker. My part of the job will be pulling and installing the cable, ready for him to inspect and connect to the main panel.

?Will connection from transfer switch to the main panel (about a 3' run) be the same size cable, or larger?
Old 02-11-2014, 03:48 PM
  #2  
Senior MemberCaptains Club Member
 
ladyjane's Avatar
 
Join Date: Jan 2008
Location: lake champlain vermont
Posts: 30,179
Likes: 0
Received 781 Likes on 496 Posts
Default

Transfer switch and 100 amp min.
Old 02-11-2014, 03:51 PM
  #3  
Senior Member
 
Join Date: Aug 2009
Location: 4 Seasons
Posts: 3,620
Received 680 Likes on 382 Posts
Default

No aluminum
Old 02-11-2014, 03:54 PM
  #4  
Senior MemberCaptains Club Member
Thread Starter
 
Join Date: Dec 2007
Posts: 15,745
Likes: 0
Received 653 Likes on 359 Posts
Default

Originally Posted by Mine Now View Post
No aluminum
They sure sell alot of it, but if copper is best, what size to use? 6?
Old 02-11-2014, 03:56 PM
  #5  
Senior MemberCaptains Club Member
Thread Starter
 
Join Date: Dec 2007
Posts: 15,745
Likes: 0
Received 653 Likes on 359 Posts
Default

Originally Posted by ladyjane View Post
Transfer switch and 100 amp min.

What I need to know is the size of cable that will run from the genset to the transfer switch. Any idea?

If the breaker is 65A for 220V, are you suggesting that the cable needs to support 100A?
Old 02-11-2014, 04:00 PM
  #6  
Senior MemberCaptains Club Member
 
ladyjane's Avatar
 
Join Date: Jan 2008
Location: lake champlain vermont
Posts: 30,179
Likes: 0
Received 781 Likes on 496 Posts
Default

I have run 2/0 for that under 8 5 feet for 100 service you can google nation electric code for a chart
Old 02-11-2014, 04:01 PM
  #7  
Senior MemberCaptains Club Member
 
Join Date: Feb 2006
Posts: 1,298
Received 424 Likes on 186 Posts
Default

Originally Posted by Mine Now View Post
No aluminum
Why not?
Old 02-11-2014, 04:02 PM
  #8  
Senior Member
 
Join Date: Jan 2007
Location: Albemarle Sound Management Area
Posts: 6,241
Received 54 Likes on 35 Posts
Default

AL 2 gauge, COP 4 gauge. Nothing wrong with AL if properly installed, that is what your service entrance is.
Old 02-11-2014, 04:04 PM
  #9  
HTV
Admirals Club Admiral's Club Member
 
Join Date: May 2009
Location: Crosby, Texas
Posts: 1,827
Received 856 Likes on 280 Posts
Default

For 65 amps #6 should be fine. But if the transfer switch is rated for 100 amp you may have to bump it up #2 and maybe #4 for the neutral to meet some code requirement. I have a 20kw which I think has an 85 amp breaker and used #4, but only had to run about 20 feet, and no problems going on 3 years.
Old 02-11-2014, 04:11 PM
  #10  
Senior Member
 
Join Date: Aug 2009
Location: 4 Seasons
Posts: 3,620
Received 680 Likes on 382 Posts
Default

Originally Posted by houtxfisher View Post
Why not?
Supposedly it expands and contracts more then copper wire, which in time causes loose connections.
Old 02-11-2014, 04:11 PM
  #11  
NFG
Member
 
Join Date: Aug 2012
Location: Maryland
Posts: 42
Likes: 0
Received 0 Likes on 0 Posts
Default

#6 THWN copper is rated for 65 amps in the 75 degree column of table 310-15. THWN is the type of insulation on the conductor. If you use the romex type of cable the insulation is a different type and not rated for 65 amps.( that may have changed by now?)
Old 02-11-2014, 04:30 PM
  #12  
NFG
Member
 
Join Date: Aug 2012
Location: Maryland
Posts: 42
Likes: 0
Received 0 Likes on 0 Posts
Default

At panel put a 65 amp breaker. From that breaker run (3) # 6 and (1) #8 ground to transfer switch. from transfer switch run same wire to generator.. What type of transfer switch do you have? Is it the type that is also a load center? You will also need control wires. 4 or 6 depending on type and age of generator.
Old 02-11-2014, 04:34 PM
  #13  
Admirals Club Admiral's Club Member
 
Join Date: Feb 2013
Posts: 1,267
Likes: 0
Received 246 Likes on 155 Posts
Default

Originally Posted by Mine Now View Post
Supposedly it expands and contracts more then copper wire, which in time causes loose connections.
That was in the old days. Different alloys used now. But a little Noalox for corrosion isn't a bad idea.
Old 02-11-2014, 04:44 PM
  #14  
Senior MemberCaptains Club Member
Thread Starter
 
Join Date: Dec 2007
Posts: 15,745
Likes: 0
Received 653 Likes on 359 Posts
Default

Originally Posted by NFG View Post
At panel put a 65 amp breaker. From that breaker run (3) # 6 and (1) #8 ground to transfer switch. from transfer switch run same wire to generator.. What type of transfer switch do you have? Is it the type that is also a load center? You will also need control wires. 4 or 6 depending on type and age of generator.
The main panel has a 100A breaker (along with several other breakers from 40 to 100A for heat, a/c, WH)

Generac RTS switch will be mounted next to/close to the main panel, so runs from main breaker to switch and back will be very small; less than 2'. The feed run from genset to switch is the long run, and your suggestion is the same as one of the supply houses for copper, so that's comforting

The electrician has installed these before, but hasn't physically looked at mine, which is why he couldn't give exact specs because I didn't know distance at that time.

FWIW, is there a huge price bump going from aluminum to copper? For what little I need, it should be nickles and dimes, shouldn't it?
Old 02-11-2014, 04:54 PM
  #15  
Senior Member
 
Join Date: Jan 2007
Location: Albemarle Sound Management Area
Posts: 6,241
Received 54 Likes on 35 Posts
Default

At 70' DO NOT run #6, you WILL regret it.

I speak from first hand experience.
Old 02-11-2014, 04:59 PM
  #16  
Admirals Club Admiral's Club Member
 
Join Date: Feb 2013
Posts: 1,267
Likes: 0
Received 246 Likes on 155 Posts
Default

# 2 URD, [3 #2 Aluminum Conductors] should run around 1.25 ft.
# 2 Copper THHN, [1 #2 conductor, you need three] should run around 1.35 ft. [3x1.35]
Just an example.
Old 02-11-2014, 05:05 PM
  #17  
NFG
Member
 
Join Date: Aug 2012
Location: Maryland
Posts: 42
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Crabpot Man View Post
At 70' DO NOT run #6, you WILL regret it.

I speak from first hand experience.
There will be little to no voltage drop at 70 feet.
Old 02-11-2014, 05:06 PM
  #18  
NFG
Member
 
Join Date: Aug 2012
Location: Maryland
Posts: 42
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by bamaboy473 View Post
The main panel has a 100A breaker (along with several other breakers from 40 to 100A for heat, a/c, WH)

Generac RTS switch will be mounted next to/close to the main panel, so runs from main breaker to switch and back will be very small; less than 2'. The feed run from genset to switch is the long run, and your suggestion is the same as one of the supply houses for copper, so that's comforting

The electrician has installed these before, but hasn't physically looked at mine, which is why he couldn't give exact specs because I didn't know distance at that time.

FWIW, is there a huge price bump going from aluminum to copper? For what little I need, it should be nickles and dimes, shouldn't it?
Your panel has a 100 amp main breaker? What kind of transfer switch do you have?
Old 02-11-2014, 05:15 PM
  #19  
Admirals Club Admiral's Club Member
 
Join Date: Feb 2013
Posts: 1,267
Likes: 0
Received 246 Likes on 155 Posts
Default

The Generac RTS series is the automatic transfer switch mention.
Old 02-11-2014, 05:21 PM
  #20  
NFG
Member
 
Join Date: Aug 2012
Location: Maryland
Posts: 42
Likes: 0
Received 0 Likes on 0 Posts
Default

Is the transfer switch strictly a transfer switch or is it also a load center?

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.