What's in the box?

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jjhoward

jjhoward

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Location
Northern NJ
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Owner TJ Electric
Pricing a job with a 100 amp sub panel in a detached garage ~120 away from the main breaker panel. About 65' of the space between main panel and sub is an elevated deck (~2'). I am thinking of running underground PVC with 2 awg CU from the main panel to a box underneath the deck. SER cable along the bottom of the deck to far side terminating in another box. From this box conduit again under ground out to the garage.

Question: What should the box have in it? Just lugs or a breaker? Is this silly, should I just stay with conduit the whole run? This method will have only 55' of conduit. A cheaper solution (if the boxes are costly.)
 
Re: What's in the box?

You need to run a main-lug panel with the breaker located at the main panel. Only use a main breaker panel on a main service. I would run all conduit. I would also use only schedule 80 pvc for any above ground PVC conduit.

Steve
 
Re: What's in the box?

Hi Steve,
Why not use a box with a main breaker on a sub?
I can still keep the neutral & ground seperate?
If I need a sub with large # of circuits, a main breaker panel can do it for me, can't it?
The question I was asking here is, if I ran concduit with 4 seperate conductors in to a small box under the deck simply to transition to SER cable, what shoudl be in that box? Or is this just a dumb idea?
 
Re: What's in the box?

JJ, you will need overload protection on the feed to the sub-panel somehow. If you have a breaker feeding the sub-panel it will be redundant to have a main-lug panel, and will cost more money.

As far as you second question goes: You can do this no problem. You will need to run the conduit into a WP box e.g. 10x10x4, you will then need to bug or crimp the connection to the SER. Come out of the box with an SER connector from the side or bottom to avoid a water drip.

It?s not a dumb idea if it is the most logical.

Steve
 
Re: What's in the box?

About the redundant breakers (DP 100 in the main panel & a the main 100 amp in the sub). If the sub is a main lug, I would still install a DP100 breaker in the sub to allow < 6 switches. Doesn't that rule also apply to sub panels?

Joe
 
Re: What's in the box?

if you overload protect the feed to the sub-panel (which you will have to do) you wont need a main breaker in the sub.
 
Re: What's in the box?

I won't need it to protect the feed from the main panel, but will I need a main breaker in this sub if I have more than 6 circuits to satisfy 230.71?
 
Re: What's in the box?

This is not a service rated panel so the main breaker is not required.

I would, if possible, go with conduit all the way as well. It will be much cleaner without the boxes and most likely much easier to not have to make the splices and install the boxes. You have to strap the cable in any case, why not just strap conduit.
Also you can make PVC do almost anything you want with heat so flexibility is probably not an issue.
 
Re: What's in the box?

I would still install a DP100 breaker in the sub to allow < 6 switches. Doesn't that rule also apply to sub panels?

Only if the sub panel is in a detached building so you are correct. See 225.31 on.

-Hal
 
Re: What's in the box?

Ok, I will run PVC all the way.
For the conductor size: Can I consider the conductors from the main breaker panel to this sub panel in another building a "feeder" per 31015(B)(6)?
 
Re: What's in the box?

JJ,
1.This is not a service lat.(art.230.71 does not apply.)
2.You are feeding this garage from a main breaker pnl. You will be connecting to a 100 amp breaker to feed from this exst. main pnl,(right?) So the the 100 amp. conductors will already be protected to the sub. pnl. at garage.
3.J.Box's cost more than lb's. Service cable cost more than conduit. Spliceing lugs and tape cost more than none at all. And,a sub pnl. with a 100 amp main cost more than a sub pnl. with just lug's.
4. You are in to this for the money. Mounting J.Box's and making spices take time.Time is money.
Although, I would,(personally), make the sub pnl. a pnl. with a 100 amp. main. Just for convience as a disconnect for the garage.
 
Re: What's in the box?

4 cond. or not, you need a grounding electrode.

If you are using 4 cond., the SER cannot be used underground. It has an un-insulated Aluminum ground.

I would use a 100a MainBreaker Loadcenter. I can buy them cheaper than an MLO panel.
 
Re: What's in the box?

[QB]
Don't you need a grounding electrode? 250.32
Click to expand...
------------------------------->Yes, he does..He will need a electrode at the separate structure thats is fed from feeder per Article 250.32 as stated.Correct me if I'm wrong,but he stated he was installing a 100 amp subpanel in Garage.Isn't that over and above requirements of Exception: of single/ multiwire branch circuit..

edited: Beat me to the button luke,I"m slow today..

[ April 04, 2005, 12:34 PM: Message edited by: dillon3c ]
Click to expand...
 
Re: What's in the box?

I am agreeing with Luke. My supplyer scratches his head on this, but a panel with a main breaker is less exspensive than a MLO Panel. This may not be true all places, but it is here.
 
Re: What's in the box?

4 cond. or not, you need a grounding electrode.

If you are using 4 cond., the SER cannot be used underground. It has an un-insulated Aluminum ground.
Click to expand...
I dont think anybody was saying to use SER under ground. The person who started the thread was asking about running conduit with 4 conductors, one being the grounding electrode. Then he wanted to end the conduit in a box located under a deck with a SER run to the sub-panel. Can this be done, yes, would I recommend it no, would I do it this way no.
 
Re: What's in the box?

Thank you all for the input. Yes, it is less $s to run the conduit and pull the 4 conductors through it. I can get 500' of 2 awg CU for $274. The 65' of SER cable would be about $75, then the two boxes wtih splices and labor, still would have some conduit at both ends with 4 conductors in them...
KISS..run the conduit, pull the conductors. But I think I need to use 1 awg to allow for temp derating. These conductors will see ambient temps at 100◦F
 
Re: What's in the box?

JJ, Make sure to watch your depth on the conduit, 18". Also make sure to use schedule 80 PVC for areas that are at risk for damage e.g. above ground.

I stick by a general rule to use schedule 40 under ground and anything above ground schedule 80. You also have other codes to consider if the conduit runs under a roadway like running rigid. You may know all this already but I thought I would just throw it out there.

Steve
 
Re: What's in the box?

4 cond. or not, you need a grounding electrode
Click to expand...
Just a quick lesson: SER has four wires, 2 hots, 1 ntrl and one GROUNDING ELECTRODE.

SER is used to feed a subpanel from the main. The main being the source of the grounding.

When you feed a main you use SEU that only has 3 conductors, 2 hots, one ntrl fed from the utility.

The moral of the story is: Use the grounding from the main by use of SER cable to feed a sub.

Steve
 
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