CurtPalme.com Home Theater Forum

Stinger72 · Joined: 01 May 2008 Posts: 53 Location: Fountain, CO

Quick question. I have a 100 amp sub panel in the basement for my theater and I need to know what gauge wire I should run from the main panel to the subpanel to supply power. My projector and gear rack are on tow separate 20 amp breakers (not sure if it matters) I think I may need 4-3, or at least 6-3. Someone told me that I could use 10-3, but I thought that was only good enough for 30 amps. Any suggestions are greatly appreciated Very Happy

dturco · Posted: Sat Jan 30, 2010 4:07 am Post subject:

Check out the minimum wire size on this panels specs.

http://www.homedepot.com/Electrical/h_d1/N-5yc1vZ1xr7Zarcd/R-100197589/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Man, I hate giving out electrical advice. This stuff should be done by someone who knows what they are doing. But I guess if there will be those who want to do stuff on their own we should at least try to help make sure its done right.

So, first question, what is the distance from the main panel to the sub panel? And not in a straight line. The path the wire will follow.

Second question, whats the amps of the main panel?

Third, will you be installing a 100 amp breaker in the main panel for the sub panel?

Stinger72 · Joined: 01 May 2008 Posts: 53 Location: Fountain, CO

The distance from the main panel to the sub with the actual lenght is 26ft...the builders left a conduit for an additional drop). I will have a 100 amp breaker in the main as well...and the main is a 150 amp.

WanMan · Joined: 19 Mar 2006 Posts: 10270

Stinger72 · Joined: 01 May 2008 Posts: 53 Location: Fountain, CO

Actually I didn't have to go too far this morning to get answers I needed (3 houses down). My neighbor is a licensed electrician in the state of Colorado and is helping me out...and it was 4-3 that I needed. So it's off to HD to get the wire!! Thumbs Up

Thanks........

WanMan · Joined: 19 Mar 2006 Posts: 10270

Good deal. Ask him if your state and county permit him to do a write-off on contractor inspection. That way if the county comes at you in the future, you have proof of work done right.

Stinger72 · Joined: 01 May 2008 Posts: 53 Location: Fountain, CO

WamMan I will definitely ask him about that. Right now I have a real hum dinger to deal with and that's trying to figure out a way to get this thick cable through this little old conduit that was left behind. At a first glance I thought it was go...now that I have the cable on site...well it just doesn't look good for the team today. Oh btw it's ran through the concrete of my foundation Shocked

Wish me luck!!!

dturco · Posted: Sat Jan 30, 2010 7:42 pm Post subject:

Use a fish tape and pulling lubricant. It's never easy , but with the lube they sell at home depot it's usually do-able.

http://www.homedepot.com/Electrical/h_d1/N-5yc1vZ1xr7Zarcd/R-100660159/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

That's assuming the conduit is the correct size to begin with.

ecrabb · Posted: Sat Jan 30, 2010 10:09 pm Post subject:

Umm... Have you guys heard of "conduit fill ratio"? The NEC specifies the number and size of conductors you can put in a piece of conduit of a given size. You can't just jam and pull as hard as you can to get whatever you want to get into a piece of conduit. You can damage or deform the wire and the lack of space in the conduit can build heat and reduce the current-carrying capability of the wire. Google "conduit fill ratio" for info, or "conduit fill chart" to see what I'm talking about.

So, if you're running 4-3 tp the subpanel, then looking at the fill ratio chart, I think you should be putting it in 1" EMT or PVC.

If you don't have 1" conduit to work with, you should be running smaller wire to the subpanel (and therefore the correspondingly smaller breaker in the main panel to protect the wiring to the subpanel).

SC

dturco · Posted: Sun Jan 31, 2010 12:03 am Post subject:

That's why I said assuming the conduit is the correct size.

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

ecrabb · Posted: Sun Jan 31, 2010 1:42 am Post subject:

Didn't I make the "why" pretty clear, Mac? According to the NEC, the 4-3 should be in 1" conduit. If he doesn't have 1" conduit, then he shouldn't run it, because the wire is oversize for the conduit - at least per the NEC.

SC

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

ecrabb · Posted: Sun Jan 31, 2010 2:41 am Post subject:

That's true, Mac... I guess I assumed you wanted/needed to use the conduit, or he wouldn't even be talking about it. Besides, you don't necessarily have to use all the capacity of the 100A panel... In fact, I question the logic of putting a 100A subpanel on a 150A main. Regardless, you could put the 100A sub-panel on a 50A breaker and only use ~half the panel, too. It all depends on how much capacity you really need in the sub-panel.

Something else just occurred to me... The fact that Stinger referred to the wire as 4-3 makes me think he's talking NM-B (Romex) - which, wouldn't go in conduit, anyway.

SC

WanMan · Joined: 19 Mar 2006 Posts: 10270

Why is a conduit being used? Is the path this sheathed conductor is taking going to be exposed to outside? Heck, my service entrance cable wasn't placed in a conduit, and its 30' to the meter, and another 35-45' to the coop box.

BTW, I had a sub-panel installed for my basement. It is 100-A, and while the distance is much shorter (2') it is exposed. Maybe this is because it is located in an interior (ahem, partition) wall and not an exterior wall.

Stinger72 · Joined: 01 May 2008 Posts: 53 Location: Fountain, CO

Well before I call it a night, I thought I would post some pics as to my situation. The main panel and blue condiut for my new run are first. As you can see it looks smaller and it actually is smaller than the cable. Yep NM sheathed..you guys are to good for me. As far as running it outside (really don't wanna do that) it may be my only option for this size of a run. Unless I can get away with running it through my garage...I tested a 10-2 wire to see if it was possible and I got good results. If I build a soffit for it..is this doable?