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davidbp 05-07-2010 12:14 PM

non current carrying conductors
 
I'm installing a 100 amp sub-panel and standby gen. recep. in my garage. I have a 1 1/2" conduit underground. I want to run the feeders to the subpanel and the conductors feeding back to the main panel in the 1 1/2" conduit. Being that only one set of current carrying conductors will be carrying current at any one time. 1.Do I have only 3 CCC's in the raceway? 2.Based on raceway fill and a 60amp breaker in main panel and a 40amp gen. what size feeders, neutral and eq. ground can I pull in conduit run? 3. Will I have 4 noncurrent carrying conductors at anytime, or do I have to count both the feeders and the ones going back to the house (even though only two hots and a neutral will be carrying current at any one time) at the same time?

joed 05-07-2010 12:43 PM

You only have 2 current carrying conductors. The neutral doesn't count. But that has no effect on conduit fill. That only affects cable derating which is different than conduit fill.

Scuba_Dave 05-07-2010 01:09 PM

Where are you located ?

davidbp 05-08-2010 05:58 PM

Quote:

Originally Posted by joed (Post 438806)
You only have 2 current carrying conductors. The neutral doesn't count. But that has no effect on conduit fill. That only affects cable derating which is different than conduit fill.

since the neutral has current flowing on it, doesn't one assume it is counted as a current carrying conductor?

codeone 05-08-2010 06:05 PM

Quote:

Originally Posted by davidbp (Post 439327)
since the neutral has current flowing on it, doesn't one assume it is counted as a current carrying conductor?

Yes the Neutral can be and is a current carrying conductor in alot of situations. It usually only carries the unbalanced load of a multiwire branch circuit for one.

joed 05-08-2010 08:02 PM

In a multiwire circuit where the neutral carries only unbalanced power it is not counted as a current carrying conductor for derating purposes.

codeone 05-08-2010 08:25 PM

Even though this is true about a multiwire circuit as you state, on a single circuit that does not have a second hot the neutral does have to be counted for derating purposes.

davidbp 05-08-2010 09:54 PM

I'm sorry I though I was being clear when I said I was talking about a subpanel and feeders and not a 220volt circuit or a balanced multiwire branch circuit. Anyway the original question remains, or part of it Do I have 3 or 5 current carrying cunductors? this responce is directed to joed

davidbp 05-08-2010 10:00 PM

Quote:

Originally Posted by joed (Post 438806)
You only have 2 current carrying conductors. The neutral doesn't count. But that has no effect on conduit fill. That only affects cable derating which is different than conduit fill.

Quote:

Originally Posted by codeone (Post 439375)
Even though this is true about a multiwire circuit as you state, on a single circuit that does not have a second hot the neutral does have to be counted for derating purposes.

What derating, with 3 ccc's in a conduit what do you derate? Don't you have to have more than 3 to start derating?

codeone 05-08-2010 10:10 PM

Just a question or two about your setup. what is your generator feeding? What kind of transfer switch are you using? Why do you have the feeder from the main panel to the sub panel and the generator feeders in the same conduit? These are questions that need answered to fully answer your question.

codeone 05-08-2010 10:19 PM

Quote:

Originally Posted by davidbp (Post 439401)
What derating, with 3 ccc's in a conduit what do you derate? Don't you have to have more than 3 to start derating?

YES that is correct. I think the original question was misunderstood. You are asking for wire fill of a conduit correct? We need to fully understand your wiring to be able to answer correctly. Depending on the situation derating if it came into play would possibly cause your wire size to go up.

Also is the subpanel going to be powered by the generator and the main too?

joed 05-09-2010 08:51 AM

Quote:

Originally Posted by davidbp (Post 439401)
What derating, with 3 ccc's in a conduit what do you derate? Don't you have to have more than 3 to start derating?

The only time current carrying is a factor is in derating which doesn't apply in this case. Conduit fill does apply however. Conduit fill doesn't care about current carrying. It only cares about the size and number of the wires and the size of the conduit.

I tried to explain that in my first post. The OP mentioned current carrying conductors in the heading of this post so that is the direction all the responses took.

davidbp 05-09-2010 02:45 PM

Quote:

Originally Posted by codeone (Post 439407)
Just a question or two about your setup. what is your generator feeding? What kind of transfer switch are you using? Why do you have the feeder from the main panel to the sub panel and the generator feeders in the same conduit? These are questions that need answered to fully answer your question.

Quote:

Originally Posted by codeone (Post 439410)
YES that is correct. I think the original question was misunderstood. You are asking for wire fill of a conduit correct? We need to fully understand your wiring to be able to answer correctly. Depending on the situation derating if it came into play would possibly cause your wire size to go up.

Also is the subpanel going to be powered by the generator and the main too?

The gen. is going to feed a 40 amp breaker in the main panel. The transfer switch is going to be a manual transfer switch on the main panel. Why do I have both sets of conductors in the same conduit is my main concern also.. is there a problem with doing it this way? From what I read it doesn't increase the # of CCC's in the conduit, but it does put a limitation on my feeder sizes because of percent of conduit fill

codeone 05-09-2010 04:03 PM

So let me see if I understand you correctly.
You have a main panel that feeds a sub panel in your garage through a conduit, and you want to install a generator plug at the sub panel and use the sub panel as a wireway to the conduit back to your main panel with a lockout breaker setup to a 40 a breaker that feeds the main and the sub panel during an outage?
Is this correct?

davidbp 05-09-2010 10:09 PM

Quote:

Originally Posted by codeone (Post 439659)
So let me see if I understand you correctly.
You have a main panel that feeds a sub panel in your garage through a conduit, and you want to install a generator plug at the sub panel and use the sub panel as a wireway to the conduit back to your main panel with a lockout breaker setup to a 40 a breaker that feeds the main and the sub panel during an outage?
Is this correct?

Most of it is, after reading your post I realized it would be easier to put a transfer switch in the sub panel and one in the main panel. The one in the subpanel I could use to disconnect the feeds to it's main breaker and feed the panel from my gen. Then I could use the 40 amp breaker to feed the main panel where the other transfer switch would be mounted. I understand that there would be 6 conductors in the raceway but, are there actually only 3 current carrying conductors in the raceway? If there only 3 ccc's what is the minimum size copper awg I can run for the 40 amp breaker and what is the max. size copper awg I can pull in for the sub panel feed? I almost forgot, what size neutral and ground also? I hope this is just a conduit fill dilemma, as apposed to having to derate because of over 3 ccc's in a raceway. Wire length is 35'.


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