Routing Cable for a Sub Panel

Reply

  #1  
Old 08-15-20, 10:37 AM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
Routing Cable for a Sub Panel

Sorry if this has been answered 100 times already but at this point I have read so much I am in information overload mode so I just need to ask.

I intend to run a 80 or 100 amp sub panel to my attached garage. My main panel is in the basement which is finished. I have drop ceiling and can get a cable from the old panel to the garage no problem. This cable will have to run perpendicular to the joists. Is it up to code to route the cable (not in conduit) through holes drilled in the joists and if so is there a specific distance they need to be from the top/bottom of the joist. If it matters my home is made with those manufactured I-Beam looking floor joists.

I read something somewhere that made me think drilling these holes and routing the cable that way may no longer be up to code but for the life of me I cant find it again.

Thanks much for any help.

If it matters I am located in Cecil County Maryland in the USA.
 
  #2  
Old 08-15-20, 11:10 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 60,936
Received 1,351 Votes on 1,249 Posts
Welcome to the forums.

Those are called manufactured I joists or just I joists. They're pretty forgiving with drilled holes unlike dimensional lumber. I can tell you drilling the holes is the easy part. Pulling a large cable thru holes that close is quite a challenge.

Holes in I joists
 
  #3  
Old 08-15-20, 11:45 AM
P
Member
Join Date: Feb 2016
Location: United States, Virginia
Posts: 1,514
Received 125 Votes on 99 Posts
May I ask what size and type cable are you planning to use?
 

Last edited by pattenp; 08-15-20 at 02:28 PM.
  #4  
Old 08-15-20, 01:22 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 60,936
Received 1,351 Votes on 1,249 Posts
I think he's asking us. Maybe 2-2-2-4 SER.

2-2-2-4 SER is just under 1" in diameter.

SER cable chart (pdf)
 
  #5  
Old 08-15-20, 01:30 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 15,224
Received 105 Votes on 91 Posts
By electrical code the holes need to be at least 1.25" from the nailing surface or protected by nail plates. However, this is not the best location to drill holes to avoid structural weakening.
 
  #6  
Old 08-15-20, 01:34 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 60,936
Received 1,351 Votes on 1,249 Posts
We're talking about I joists..... a top and bottom 2x4 connected with oriented strand flake board.
Typically the center area is 6-10" depending on joist size. Many have knockouts if you look close.

 
  #7  
Old 08-15-20, 02:21 PM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
The pic above is the correct joist and there are some knock outs. I actually already have a large cable pulled this way for a heater in the garage. I am going to pull that out and replace it with a larger cable and install the sub panel so my path is clear. I was really just trying to confirm there is no code violation running it that way. Something I read lead me to believe there might be.

I did the previous one on my own and didn't have it inspected or anything. This time I want to make sure everything is on the up and up and will likely just rough it in myself and have a real electrician do the hookup and call for inspection.

I believe I need to use this cable
https://www.homedepot.com/p/Southwir...dalType=drawer

Any feedback is welcome
 
  #8  
Old 08-15-20, 02:31 PM
P
Member
Join Date: Feb 2016
Location: United States, Virginia
Posts: 1,514
Received 125 Votes on 99 Posts
Just an FYI, 2-2-2-4 AL SER is 90 amps, 1-1-1-3 AL SER is 100 amps.
 
  #9  
Old 08-15-20, 03:08 PM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
Thanks I will make sure I buy the 1-1-1-3.

Is it safe to say my running the cable through the joists like this is safe and likely up to code?
 
  #10  
Old 08-15-20, 06:39 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 13,808
Received 253 Votes on 221 Posts
Unless you are running a machine shop in your garage you will likely be fine with 90 amps.
 
  #11  
Old 08-16-20, 06:47 AM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
If I stick with the smaller wire and only go with 90amps is it acceptable for the main breaker in the garage panel to be 100amp as long as the one in the main panel is 90 or smaller?
 
  #12  
Old 08-16-20, 07:44 AM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: United States
Posts: 13,808
Received 253 Votes on 221 Posts
Yes. The 100 amp breaker in the sub will only be a disconnect. The breaker in the main panel provides the overcurrent protection required.
 
  #13  
Old 08-21-20, 07:10 AM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
I appreciate all the feedback so far, many thanks.

Can someone tell me if what I am doing in this diagram is acceptable? Curious if the transition from this being and interior to exterior wall has any bearing on anything.

Also I would very much like to put some protection behind this cable to prevent nails/screws from getting driven into it from the inside. I have read there is some kind of metal shield/blocking that I can place behind the cable to prevent this. Can someone confirm that and tell me what the name of the product is so I can find it?

Once again many thanks.


 
  #14  
Old 08-21-20, 07:28 AM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
One more follow up... Is it permissible to use MC Cable in a garage for all the branch circuits instead of conduit? If that is acceptable it would be perfect since there are only going to be a handful and all will be dedicated each for an individual big tool (table saw, planer, etc).
 
  #15  
Old 08-21-20, 07:52 AM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
Hmm... Probably should have read a little more prior to posting. I see a requirement for the MC cable to be 8' off the floor if exposed. I see that fittings are available for transitioning from MC to EMT. Would it be acceptable to come out of the top (or sides) of the panel with MC, run straight up to the ceiling and over to the outlet location, and then transition to EMT keeping that MC higher than 8ft off the ground (ceiling is 11 ft high) ?

If that works it would probably be my best bet. This garage is a woodshop and every couple of years I get a new big tool or reorganize the shop. If I can feed the power this way it makes that process super easy compared to other methods.

So to summarize my questions:
  • Does the picture of my panel installation above present any problems?
  • What can I place behind the cable in the wall to protect it from interior screw/nail damage?
  • Is going from MC to EMT for the branch circuits in the garage seem reasonable and up to code?
Once again - many thanks.
 
  #16  
Old 08-21-20, 01:52 PM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
My problems have become a little more complicated and have deviated from my original post so I am going to stop and make a new thread.

Thanks again
 
  #17  
Old 08-21-20, 02:11 PM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
Advice on Routing Wire and Conduit

I am attempting to install a new sub panel in my attached garage. Could someone take a look at the picture below and give me some advice on how to make sure I do this to code.

My plan is to use some 1-1-1-3 SER Aluminum cable to come thru my basement and pop out into the garage. The attached picture shows in red where the cable would come up from the basement and where it changes to blue is where I would begin with the conduit. I plan on surface mounting the new panel on top of new 5/8 drywall and will put some backer board behind it to offer the box proper support.

Anyone see issue with this? What is the correct way to come out of the wall and into conduit?

Thanks in advance





 
  #18  
Old 08-21-20, 03:17 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 60,936
Received 1,351 Votes on 1,249 Posts
Threads combined. You deviated from your original plans but this is still your thread so you change anything you want. We try to keep like topics in one thread to eliminate duplicate questions.

You can use what is called an LB to bring the wire out. Keep in mind..... it is extremely difficult to pull this cable in conduit. It doesn't bend easily.
 
  #19  
Old 08-21-20, 08:14 PM
pcboss's Avatar
Forum Topic Moderator
Join Date: Jul 2002
Location: Maryland
Posts: 15,224
Received 105 Votes on 91 Posts
I would just sleeve the cable in a conduit to the panel. Is there a reason you don't want the panel close to where it exits the basement?
 
  #20  
Old 08-22-20, 06:07 AM
P
Member
Join Date: Feb 2016
Location: United States, Virginia
Posts: 1,514
Received 125 Votes on 99 Posts
The panel needs to be placed where you can stand in front of it with no obstruction 36in of the front by 30in wide. Is that a built in bench in the picture at the panel location?
 
  #21  
Old 08-22-20, 07:09 AM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
The bench is actually why it needs to go toward the front. The bench in the picture is slid out of the way but when its reinstalled it will block it if I don't move the panel to where I have it on the drawing.
 
  #22  
Old 08-22-20, 08:39 AM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
Ok... Due to other non-electrical related factors I have decided to just mount the panel directly over where the cable comes up out of the basement and throw away the workbench and make a new one. That reduces my level of complexity pretty significantly. With that in mind my last question (I hope) is can I just go directly into the back of the new panel with the cable or do I need to pop out of the wall into an LB and use a short stub of conduit into the box?

 
  #23  
Old 08-22-20, 09:06 AM
P
Member
Join Date: Feb 2016
Location: United States, Virginia
Posts: 1,514
Received 125 Votes on 99 Posts
I'd just jog the cable out of the wall and come in the bottom of the panel and use a NM clamp to secure the SER cable to the panel. Then make a wood chase to cover the short section of exposed SER. You can come in the back if you have a lower corner back knockout but you may find it hard to bend the cable to manage it through the hole.
 
  #24  
Old 08-22-20, 09:42 AM
W
Member
Thread Starter
Join Date: Aug 2020
Posts: 18
Received 0 Votes on 0 Posts
If a small wooden chase is acceptable then that seems like the path of least resistance for sure. Thanks so much.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: