This XHHW cable OK for 100amp basement sub panel?

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  #1  
Old 03-23-15, 12:17 PM
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This XHHW wire OK for 100amp basement sub panel?

Hello all, I've been doing a lot of research and just wanted to get some second opinions before making some purchases.

Project: I'm in the process of finishing my basement, I have a main electrical panel in my gararge (150amp) square D. It's about 30ft as the crow flies to my basement, and roughly 55ft in an EMT conduit run.

What I'm looking to purchase.

1: 2" EMT conduit to run from the main panel to the basement sub panel

2: Square D sub panel (with 100 amp breaker) for installation in basement, so I'd have 1 x 100amp in the main panel and 1 x 100amp in the sub for shut off at either end.

3: This XHHW wire for the 100amp panel (I'd be running 3 #2 for 2 hot and 1 nuetral and 1 #4 wire for ground).
Southwire 500 ft. 2-Gauge Stranded XHHW Wire - Black-11272207 - The Home Depot

I just wanted to double check that it's common practice to use that wire inside EMT conduit, it seems that it's slightly better rated and easier to pull than the THHN/THWN.

Thoughts/suggestions are appreciated.
 

Last edited by jlrosine; 03-23-15 at 02:08 PM.
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  #2  
Old 03-23-15, 01:34 PM
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No need for the breaker in the basement sub panel.XHHW if fine, use Nolax on the Al.,not code but a good practice .
Geo
 
  #3  
Old 03-23-15, 01:46 PM
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Also, this is XHHW insulated aluminum conductors, not cable. A cable is a factory made combination of two or more conductors with an over jacket or where the individual conductors are twisted together.
 
  #4  
Old 03-24-15, 09:05 AM
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The overkill is not necessary, just wasted dollars in my opinion. You do not need the 100 amp main breaker in the basement subpanel. The whole house is just fed with 150 amps, why would you need 100 amps just for basement finish when 60 amps would be well more than sufficient? I would feed the basement with a 60 amp 2 pole breaker in the main panel using 6-3 NM-B cable (copper) as the feeder to a main lug panel in the basement.

I just wanted to double check that it's common practice to use that wire inside EMT conduit, it seems that it's slightly better rated and easier to pull than the THHN/THWN.
If you use XHHW conductors they MUST be in conduit. I would almost always use THHN/THWN copper conductors over aluminum XHHW because of these ease of pulling. Remember, if you use aluminum XHHW conductors you are pulling wire that is 1 to 2 sizes larger to carry the same amperage.
 
  #5  
Old 03-24-15, 10:48 AM
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Thanks Joe for the insight, just a few comments....

You do not need the 100 amp main breaker in the basement subpanel. The whole house is just fed with 150 amps,
I'm going to have some pretty decent size electric baseboard heaters in the basement, and I'm also relocating my washer/dryer down there (it was on main level), in addition to my outlets and lighting, those are the main two reasons I chose 100amp, and it just doesn't cost much more IMO (If I ever wanted to upgrade the main, the basement would probably already be slightly overbuilt). The basement is around 1,200sq/ft.

I would almost always use THHN/THWN copper conductors over aluminum XHHW because of these ease of pulling.
If you are worried about wasted dollars, the copper THHN is $158.40 compared to the aluminum XHHW at $54.00 for 180ft.

Is it going to be drastically different to pull THHN (more rigid) #3 copper vs (XHHW slightly less rigid) alum #2? I'm going to have probably 3 to 4 90degree bends (long bends).

Thanks again for the feedback.
 
  #6  
Old 03-24-15, 07:35 PM
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Keep in mind that #2 AL is only good for 90 amps as a feeder.
 
  #7  
Old 03-25-15, 01:55 AM
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Have you considered SER cable?
 
  #8  
Old 03-25-15, 07:23 AM
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Have you considered SER cable?
Yes initially I was going to get SER but you can't run that in conduit. My garage is finished and textured so I didn't want to cut/drill holes etc....

Conduit just seems a lot easier at this point, but the cable is a bit more pricey.
 
  #9  
Old 03-25-15, 08:20 AM
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SER does not need to be run in conduit. It can be run on the surface. Protection would only be needed if subject to damage.
 
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Old 03-25-15, 08:23 AM
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I think you misread....you aren't allowed/can't run SER in conduit, which is what I said.

The problem with protection is....you can't run a 100amp cable and just lay it around. I'd guess any inspector would frown upon a cable just attached to a wall or on some surface...seems half ass'd to me, no?
 
  #11  
Old 03-25-15, 11:44 AM
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It can be run on the surface where not subject to damage. It can also be sleeved in conduit to protect it from damage.
 
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Old 03-25-15, 11:55 AM
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I guess I would wonder what the inspector might consider "subject to damage", I guess I'd have to call and ask them.

How can it be sleeved in conduit? Isn't the big issue heat? I thought that was why you can't run SER in conduit...there's no ventilation. My inspector said SER in conduit would not be advised, and I don't think it would pass inspection, though you may know of something I'm not aware of.

Thanks for the advice.
 
  #13  
Old 03-25-15, 11:58 AM
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Generally above 6'7" (2 meters) it is considered protected so you can sleeve vertically to that height or grater and then run fastened to the wall.
 
  #14  
Old 03-25-15, 12:58 PM
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OK, now I'm warming up to this idea since the SER would cost me about $110 total. What would I use specifically to sleeve the SER cable above ground (indoors)? Here's what I'd be doing.

- My main panel is located inside my garage on a textured sheetrock wall. I'd be connecting the SER cable directly in to the top of the main panel and to the appropriate connections inside the main, and the 100-amp breaker.

- I could fish the SER cable from a spot higher than 6' 7" inside the sheetrock down to the main panel, or does this still need to be sleeved inside the rock?

- I'd then fasten the SER to the sheetrock at about 9ft high, it would run about 23ft until I can drop straight down in to a sleeve, then in to the basement. I'm guessing I could use a 10ft piece of PVC for this sleeve?

Thanks for the help/suggestions.
 
  #15  
Old 03-25-15, 01:33 PM
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What would I use specifically to sleeve the SER cable above ground (indoors)?
PVC conduit or EMT. EMT would require bushings.
I could fish the SER cable from a spot higher than 6' 7" inside the sheetrock down to the main panel, or does this still need to be sleeved inside the rock?
No sleeve if fished in the wall. Your overall plan is good.

230.51A:
Service Cables. Service cables shall be supported by straps or other approved means within 300 mm (12 in.) of every service head, gooseneck, or connection to a raceway or enclosure and at intervals not exceeding 750 mm (30 in.).
Source NEC
 

Last edited by ray2047; 03-25-15 at 01:49 PM.
  #16  
Old 03-25-15, 03:04 PM
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Ray, you included some magic words in that response, service cables. The word service has a very specific meaning in the NEC and it applies to the wiring between the utility's connection and the first fuse or circuit breaker. That is the ONLY place that the word service is applicable.

Further, Article 230 deals specifically with services and is generally not applicable to non-service wiring. Just because a person uses cable made for services does not make the installation a service.
 
  #17  
Old 03-25-15, 03:38 PM
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I agree. The circuit the OP is describing is an Article 215 feeder. Supporting requirements for SE cable are the same as for NM (338.10(A)(4) refers to part II of Art. 334).
 
  #18  
Old 03-25-15, 03:43 PM
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OOOPs guys. Thanks for the correction.
 
  #19  
Old 03-25-15, 04:08 PM
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If you are worried about wasted dollars, the copper THHN is $158.40 compared to the aluminum XHHW at $54.00 for 180ft.
In most cases I don't consider the higher price of copper versus the lower price of aluminum a waste.

Specifically, I was referring to an unneeded main breaker in the basement subpanel and a 100 amp feeder to the basement. You have now somewhat explained the need for the 100 amps although I don't believe you have done a load calculation. In this case though, I concur that a 100 amp feeder to the subpanel isn't a bad idea.

I have to agree that using SER cable is usually a pretty good way to go for what you are trying to accomplish. It always feels good when a plan starts coming together.
 
  #20  
Old 03-25-15, 04:31 PM
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Subject to damage is entirely subjective. I would not consider cable that high above the floor to be subject to damage. A sleeve coming down where the cable enters the basement sounds like a solid idea.
 
  #21  
Old 03-25-15, 07:35 PM
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Thanks everyone, I really appreciate all of the help/feedback. I feel a lot better now about the solution. I had my inspector verify my plan and he gave it the "in theory" thumbs up.

Joe, your right I didn't do a really formal calculation, though I did have an electrician do an entire basement quote for me and he had a 100-amp in the plan too. His calculation was based on my visio diagram of all of my lights/switches/baseboard heaters etc. Initially he was going to go with a 60-amp I think, then once I added washer/dryer/potential wet bar area, he recommended 100 too. I was also going to put a 100-amp breaker in the basement only for convenience to be able to turn it on/off as I run wire and new circuits down there....because I'm lazy and don't want to hike up to the garage. I realize though I probably don't need it, and probably could just make the walk to test.

Thanks again all!

-Jeremy
 
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