This doesnt seem right.

Stubbie · 01-24-2007, 08:49 PM

Quote:

But I was thinking in the future it would be nice to run power to my shed from this panel. Just a small panel to run a plug and light. Would that even be legal? Never considered it until now.

Sorry, I didnt catch this question on the 1st read. Yes, you can run a 240V feed to another panel from your sub-panel or run a 20 amp or less 120 volt circuit to a snap switch in the shed and from that to lights and receptacles. A buried UF-B cable would be fine for this application. I would just post back when the time comes and someone here will answer your questions.

Stubbie

JoulesWinfield · 01-25-2007, 07:09 AM

Thanks again.

When I get time and probably warmer weather I will check into what size breaker I want to stick with and then go get the cable from the electrical supply we use here at work. Most likely going to go with a 60 amp since that would be much cheaper.

Thanks to everyone who responded.

Stubbie · 01-25-2007, 11:33 AM

I think that makes good sense given the cost of wire these days. Just so you will know the big box will carry NM-B #6 awg copper cable, the NEC requires you to limit the ampacity to 55 amps but you are allowed to breaker it at 60 amps. It's a special requirement for nm-b cable that you must use the ampacity in the 60C column of table 310.16 (see NEC art. 334.80). If you can get an SER cable in copper #6 you can use 65 amps and protect it with a 70 amp breaker. Otherwise a #4 SER aluminum cable will give 65 amps and you can put it on a 70 amp breaker. The reason for this is an ocpd rule we call the "next size-up rule". There are no 55,65,75,85,95,105,115... circuit breakers (see NEC art. 240.6)(A) so when your ampacity falls in between for example 50 and 60 amps you are allowed to go to the next size up which would be a 60 amp breaker. Most cables (other than nm-b or uf-b) are allowed to use the 75C column of 310.16 for ampacities. Basically if the wire has insulation matching the types in the 75C column or the 90C column it can use the 75C ampacities.... other than the exceptions noted. Do not use the 90C column ampacities.

Stubbie

JoulesWinfield · 01-25-2007, 02:03 PM

Great info thanks.

Itll be a while before I dive into this as Im in the middle of finishing a new bedroom in my basement. Which is how I came across the wiring for the garage.(

"whats this cable for?")

I think I will shoot for the 70 amp depending on the price diffrence at the time. Im guessing it will be a couple hundred since the run is about 80-90 feet.

But making sure no one dies or that my house doesnt burn down is priceless.

JoulesWinfield · 01-25-2007, 07:26 PM

I had a thought on the way home tonight.

Could I just run a new two wire the same size as whats there and use the new one for the neutral and ground connection?

I could tie the braided grounds togather and I would just end up with a spare wire.

I dont think Ive seen any code anywhere that says the feeder has to be in one cable.

Speedy Petey · 01-25-2007, 08:13 PM

Quote:

Originally Posted by JoulesWinfield

I dont think Ive seen any code anywhere that says the feeder has to be in one cable.

"You don't think..." ?
Keep reading. You'll find it.

JoulesWinfield · 01-26-2007, 08:08 AM

That sounds like a NO.

I dug around for a while and cant seem to find it. Not a problem though.
If the experts here say its not a good idea, then I will run a new 4 conductor. I dont need 100amps anyways.

Thanks again.

Stubbie · 01-26-2007, 03:45 PM

Joules.... take a look in article 300 "Wiring Methods". Article 300 covers all wiring installations unless specifically modified by other articles dealing with feeders. Article 215 covers feeders.
If you still cant find it post back and we will narrow it down. You seem to like to learn so read and chase down all the refered article sections, once you find the one that answers your question. These other "refered" articles specifically give the situation needed to do what you are asking.

Stubbie

JoulesWinfield · 01-26-2007, 05:40 PM

I have been going over Article 215, but I dont remember if I went through article 300 completely or not. Ive been reading a lot of code since I posted the topic originally.

You are right I do like to learn though and I appreciate everyones help here. I almost wish I would have kept doing residential electrical way back when (only did it for a couple of weeks) just so I would know all this stuff. Instead I went back to doing to machine tool electrical and ended up becoming a controls engineer. It was a lot more challenging than wireing up the same machines over and over. And we never went over much code since it was "special equipment" until NEC2005.

Anyways when I get back to work monday Ill look it up.

Thanks.

JoulesWinfield · 01-29-2007, 07:58 AM

So from what I can tell, and correct me if Im wrong, the only way I would be able to run two cables for the same feeder is if this were a parallel instalation. Meaning that I was splitting the load between two cables not seperating parts of the same feeder between two cables.

I am going to read through this again later today, my brain starts to melt if I spend too much time reading technical literature without a break.

Also I decided to take my 2002 book home as Michigan is still on 2002 and at work I pretty much have to use 2005. (Even though the company doesnt own a copy of NEC2005).

So when Im reading stuff on here were you guys are quoting from "the code" I will be following along at home.

Stubbie · 01-29-2007, 02:55 PM

Yep, you got it right. The codes are 300.3(B) and (B)(1) for conductors and more specifically underground installations of circuits is 300.5 (I).

Stubbie

Power Up · 07-26-2009, 07:41 PM

Quote:

Originally Posted by Stubbie

Hello

You have several code viloations for the installation of a sub-panel in the same structure as the dwelling.

These violations are:

1.) Feeding from the line side of the service equipment main breaker (using its lugs) to a sub-panel.
2.) No ocpd protecting the feeder.
3.) A 3 wire feeder (needs to be a 4 wire feeder...ie..(H-H-N-Grd)
4.) No ground rod at the sub is to be used in this application other than the ground rod/rods and possible metal water pipe at the service panel (main panel).
5.) No seperation of equipment ground from the grounded conductor
at the sub-panel. You cant accomplish this without a seperate equipment ground ran to the sub-panel.

#2 al is only good for 90 amps 75C terminations but that should be fine for your purposes.

In the set-up as it exists presently the metal can of the sub-panel can become energized on fault from the feeder or a branch circuit ungrounded conductor and there would be no way to trip a breaker since there is no breaker protecting the feeder and no bond to the can of the sub-panel.

This is no good... you need a 4 wire feeder from a breaker installed in the main panel. You would then install a seperate ground bar for the grounds in the sub-panel. You would not bond the ground and neutral in the sub with a 4 wire feeder and you will not use a ground rod at the sub. If you use the #2 al you would use a 90 amp breaker or less in the main panel.

Stubbie

The min. conductor size for Dwelling services which would include sub feeders is # 2 al or #4 cu.

InPhase277 · 07-26-2009, 08:40 PM

The last post in the thread is over two years old. I imagine they've figured it out by now.