Wire for sub-panel

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  #1  
Old 07-21-13, 09:26 AM
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Wire for sub-panel

I need to add a sub panel in my attached garage. The reason being that I'm out of breaker slots on my main 200A panel due to the fact that I currently have 6 circuits running to the garage 2x 30A 115 for the heaters (4 heaters @ 12.5A), 2 115 for two sets of outlets (so i can run the bandsaw while using other tools without blowing a breaker), 1 for the AC, 1 for 230VAC (mill). I need to add two more, and one in the basement, so i think it's time. I've decided that a 100A subpanel would give me plenty of room to add dedicated circuits (I have a few pieces of equipment on my wish list)

Q1: I have plenty of 4AWG CU wire, but cannot find a definitive answer as to whether it's legal. Here's the marking: "4AWG E51293(UL) MTW OR THW OR AWM 1232/1283/1337 600V VW-1 --- LL22035 CSA TEW OR AWM 0 600V 105C W750C FT1 I A/E" Can anyone tell me if this is legal wire for feeding the subpanel L1, L2 & N? If not, I'll just go to HD and get whatever they tell me is the preferred wire, but I'd rather not spend the $$$ if I don't have to.

Q2: The wall it's going on is the one that separates the garage and the house. Once I attach some wood (whatever I can find that is sturdy) to the wall, mount the box, and pull the feed wire into the garage, I feel it will be unprotected from me dragging stuff around, carrying metal, etc. I could drill holes back through the wall (2x 3/4" OSB + 3/4" drywall), and then route through the walls, but I know that wall is some sort of firewall of sorts, and am not sure the code on drilling several holes in it. Is this OK? I really want to encase it in a cabinet as well, but I've read this violates code (no cabinets, countertops, etc). Is there a better way to protect / hide it that is legal?

Q3: I have an odd back 3ft of the garage, in that I cannot run wiring from the walls to the attic / ceiling without drilling through an I-beam (which I won't do). I have cabinets along one side and around the corner. They are against a footer on the side, and matched distance on the back. so not all the way against the wall. Is it legal to use that area between the cabinet and the wall, on top of the footer / floor as a "wireway" to avoid tearing out tons of drywall to drill through studs and run wire horizontally?
 
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Old 07-21-13, 09:46 AM
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THW #4 is only good for 85 amps (75C). You seem to be planning to run them without conduit. That is not permitted.
 
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Old 07-21-13, 10:03 AM
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Welcome to the forums!

Q1) Yes, that wire is OK as long as it is installed in a raceway (conduit or a fitting like an offset nipple) It is THW which is only rated at 85 amps which means you will need to protect it with a 90 amp breaker or less.

Q2) The wall separating the garage and house is considered a fire wall in many places. All that really means is that any penetration through the sheetrock needs to be sealed. The wire feeding the panel needs to be protected. (See above about your #4) If you feed it with cable it either needs to be in the wall space or in conduit.

Q3) If it was me, I would install the panel on the surface of the drywall and run all your new circuits on the surface in conduit. You could use wither PVC or EMT. Both have prebent fittings if you are not very good with an EMT bender. You can then change or add to your electrical layout as needed in the future.
 
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Old 07-21-13, 11:51 AM
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I currently have 6 circuits running to the garage 2x 30A 115 for the heaters (4 heaters @ 12.5A), 2 115 for two sets of outlets (so i can run the bandsaw while using other tools without blowing a breaker), 1 for the AC, 1 for 230VAC (mill).
I would remove these circuits from the main panel in the basement and refeed them from the new subpanel in the garage. That would free up space in the main panel for the new circuit you wanted down there. The two 30 amp circuits, each for two 12.5 amp heater loads, is questionable. If these are typical plug-in heaters, those heaters should each be on a 20 amp circuit.
 
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Old 07-21-13, 02:36 PM
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Ok, so the #4 THW is good for 85A when run inside conduit. Now that I know that, I guess the question becomes do I go and buy a bunch of conduit or just some 2-2-2-4 AL. I ran down to HD and they have this: Southwire 500 ft. 2-2-2-4 3E AL SER Service Entry Electrical Cable-13102915 at The Home Depot in stock, by the foot. It would be about $90 to get enough of that to do the job. My main panel is below grade (in the basement), and the feeder to the new panel would be above grade, from the basement to the garage (garage is not over the basement, but they share a wall.)Is a conduit also required when using a cable like this with an outer jacket? I'm thinking this could save me hours of bending conduit if it was acceptable.

I'm not totally opposed to running surface conduit, and I have a couple of benders that I've used in the past (it's been awhile, but I could manage. It would, however be extremely convienient to run some of the wiring between the cabinets and the wall / floor / footer. No conduit, short runs in the walls, etc. It would be 12-2 or 10-2 romex. Other personal preference, is there any reason not to do this?
 
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Old 07-21-13, 05:15 PM
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I guess the question becomes do I go and buy a bunch of conduit or just some 2-2-2-4 AL... Is a conduit also required when using a cable like this with an outer jacket? I'm thinking this could save me hours of bending conduit if it was acceptable.
A cable is not installed in conduit. It may be protected from physical damage by a conduit sleeve for a short distance.

Your options for the feeders from your existing panel to your proposed subpanel are either individual conductors in conduit or cable inside walls and other structures.

It would, however be extremely convienient to run some of the wiring between the cabinets and the wall / floor / footer. No conduit, short runs in the walls, etc. It would be 12-2 or 10-2 romex. Other personal preference, is there any reason not to do this?
Can you post a picture or drawing of the space you're talking about? Is it totally enclosed?
 
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Old 07-21-13, 06:32 PM
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Nashkat1
A cable is not installed in conduit. It may be protected from physical damage by a conduit sleeve for a short distance.
Good, no conduit for me.

I've seen that AL 2-2-2-4 is rated for 90A, and should be protected by 100A breaker. That sounds good, but that seems to be for the main, not branch circuits (75A for those). Can someone explain to me the logic behind this difference? For given temperatures, wire should be able to carry a given current, or so I thought.
 
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Old 07-21-13, 07:38 PM
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It is not the wire so much as the thermal characteristics of the insulation. The higher temperature the insulation can handle the more amps within the limitations of the actual wire size. Put another way it isn't how many amps will melt the wire. It is how many amps will melt the insulation.
 
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Old 07-21-13, 08:35 PM
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Originally Posted by Nashkat1
A cable is not installed in conduit. It may be protected from physical damage by a conduit sleeve for a short distance.
Good, no conduit for me.
Originally Posted by Nashkat1
Your options for the feeders from your existing panel to your proposed subpanel are either individual conductors in conduit or cable inside walls and other structures.
If I'm hearing you correctly, that means you're choosing to run cable for your feeders, keeping it inside the walls and other framed spaces everywhere. Is that right?

It would, however be extremely convienient to run some of the wiring between the cabinets and the wall / floor / footer. No conduit, short runs in the walls, etc. It would be 12-2 or 10-2 romex. Other personal preference, is there any reason not to do this?
Originally Posted by Nashkat1
Can you post a picture or drawing of the space you're talking about? Is it totally enclosed?
 
  #10  
Old 07-22-13, 06:30 AM
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Yes, I'm choosing to run cable, and keeping it inside the walls / framed spaces EXCEPT: 1. between where it exits the main panel and runs up the unfinished basement wall into the joists above, and 2. between the sub-panel and the hole in the "firewall" where it exits.

For #2, I am considering running it out a hole that is aligned with one of the rear knockouts in the subpanel, but I'm not sure how i would do a cable clamp when the panel is mounted flush. A second option would be coming out the top / bottom, but i'm not sure how to "finish out" the transition from subpanel box to air then through the firewall without it looking weird. I'd almost like to see a conduit coming out of the box and into the wall, but don't want to run conduit beyond that.

I'll get some pics of the cabinet situation, which is downstream from the subpanel
 
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Old 07-22-13, 08:55 AM
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OK, sounds like a plan. As far as I can tell, there isn't a 90[SUP]o[/SUP] cable connector available for the cable you're planning to run, and the cable has a minimum bending radius which you might not be able to achieve in the wall to get you into a straight connector.

A short offset, which you might be able to find pre-bent, can be used to sleeve it into the wall from either the top or bottom. It will need a knock-on bushing to protect the cable sheath at the open end, inside the wall.
 
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