Subpanel question

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  #1  
Old 10-20-13, 05:29 AM
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Subpanel question

My apologies if this have been covered:

I have a main service panel located on the OUTSIDE of my outbuilding. This panel has a 200A breaker in it that feeds the house. It also has a second 200A breaker that I would like to use to feed a panel for the inside wiring of the outbuilding (thus now delaring it, something passible, as a 'shop')

BUT - I need to wire from this 200A breaker on the outside, to feed the inside panel.

The way its mounted has everything flip flopped - meaning the breaker on the outside panel would naturally feed out of the right hand side of this box, but then I would need to go up, across the top to the left, before going through the wall and into the inside box. Conduit would look pretty ugly for this. Service entrance wire might look worse (Im trying to make a nice clean job of it)

I could go straight through the wall to the inside - and then have standard 2x4 framing. I assume the feed wire would all need to be contained in conduit if I go through the wall - but then I would have to go all the way through and have exposed conduit inside, which would then go back into the inside panel which is flush mounted to the interior wall.

I guess I could pull the inside panel out so it didnt mount flush - just thought of this option.

Can I run conduit inside of an insulated wall? (I dont think this really works anyway, because I have to go through a wall stud and the hole would be too large)

Can I run service entrance wire through a wall?

Can I run some other wire - separates would be ideal, through an interior wall to feed a panel?

Thoughts/recommendations? (I can likely get some pics up - I know is always helpful)
 
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  #2  
Old 10-20-13, 07:52 AM
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Thoughts/recommendations?
My first thought is you don't need anywhere near 200 amps for a shop. Can you install a smaller 2 pole breaker in the panel; perhaps a 60 amp 2 pole? The conduit/wire you'd be working with would be substantially smaller and easier to work with.
 
  #3  
Old 10-20-13, 08:10 AM
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I agree Joe - and the answer is from a practical sense, its already there. (and these large breakers in this panel cannot be cheap at all). But I will see what it would cost to bump down to a 100A breaker - which would match the inside panel better anyway.

Originally the shop started out with a 100A panel. The largest item I have is a 15hp induction motor for a widebelt sander, with a 1hp conveyor running at the same time plus lights/etc. Then someday I might add a welder (these two are likely my largest loads). Startup current on the large induction motor pulls some juice.

BUT - the outside panel with the 200A break is in and done. Wasnt how I was going to do it originally but through a long winding road its how it ended up. Not a disaster by any means, and it will be a great install when done. The house side came out great.

I just need to sort out how to go from the outside 200A panel to the inside panel (currently 100A, but I may just pull it and put in a 200A panel to match the outside breaker, or as mentioned get a 100A breaker on the outside).

Overkill. Yep. By a lot.
 
  #4  
Old 10-20-13, 09:39 AM
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Pictures are always welcome and helpful.
http://www.doityourself.com/forum/el...-pictures.html
 
  #5  
Old 10-20-13, 12:41 PM
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The panel from the outside prior to hookup:



And the breakers:



And this one shows a crude outline of where the inside panel sits, partially behind the outside panel. I need to go from the lower right outside, through the wall and into the inside panel. If I could just punch through on the lower right and then once inside I could go right across to the inside panel - BUT - I need to go through a 2x4 stud and putting it all in a conduit would be way to big a hole through the stud (I try to stay with 1" hole on center). I could split it into a couple wires and put two each in smaller conduit - might be one option. Or a short piece of service entrance wire - but Im not sure if its allowed to be run in an inside wall (and to be honest I much prefer the idea of putting it all in conduit, just so a screw doesnt get run through it as easily)

Or come out the right side and conduit up and across the top and then through/into the inside panel. This puts a section of conduit on the outside.

Im hoping to get something very 'clean' looking, even if it takes a little more work.




And I suppose I could move the inside stud over a few inches and put a header and give a bigger space to work with - could just go through, and then straight over and put it all in conduit.
 
  #6  
Old 10-20-13, 04:50 PM
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Is it just me or do those conductors look really small for 200 ampere overcurrent protection?
 
  #7  
Old 10-20-13, 05:28 PM
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They do look small in the picture Furd, but in reality the box is pretty large.

What you see on the incoming side are two sets of three each 4/0 AL (yellow for ground). So 6 cuts - two 4/0 sets in parallel incoming. These are approximately 160ft to the street.

Then on the outgoing side are three 250mil Al cuts, and a #4 Cu ground. These run about 175 - 180 ft to the house. (overall a fair distance from street to house, but with the first section in parallel and the second section at 250mil it should be pretty decent for a 200A service).

The liklihood of pulling 200A at both the shop and the house at one time is about zero imo (just saying its unlikely, so this seemed sufficient to me)

Its 3" PVC on both sides.

The wires prewired to the breakers are Copper - Im not sure the guage but they are bigger than the picture makes it all appear (it was a prewired box and Im comfortable they are sized appropriately).

My latest thoughts are to move the stud and just go through the wall directly and put conduit inside the wall. Given its about 2ft - 2/0 Copper should do it. 2" conduit should fit.
 
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Old 10-20-13, 06:04 PM
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Yes....definitely go thru back of main panel to garage panel. You don't really want any connections in the top of that main panel.
 
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Old 10-20-13, 06:11 PM
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OK, I see now. What you have is a 400 amp Milbank meter socket with two 200 amp breakers. Now that I see the pictures, I don't believe changing the breaker to 100 amps is a logical move. The factory installed 3/0 conductors will not fit the lugs on a 100 amp breaker and I doubt the frame size of a 100 amp breaker would fit. Besides that, I know from past experience that Milbank breakers have to be ordered and take several weeks to get and they are pretty pricey. What may make more sense is to use a 250 MCM AL SER cable and exit the socket through the back at the lower right knockout and then continue to the new panel location............OR............ use 2" conduit with copper THHN conductors like you mentioned, but I think you should use 3/0 instead of 2/0. I know 2/0 copper is allowed for a 200 amp residential service, but this isn't service entrance wiring, it's a 200 amp branch feeder. Check with your local AHJ to confirm the size they will approve.

Furd
Is it just me or do those conductors look really small for 200 ampere overcurrent protection?
I believe the breakers are pre-wired with 3/0 copper, can't tell what type.
 
  #10  
Old 10-21-13, 09:58 AM
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I do think conduit is the way to go.

But for my own education - can service entrance wire be used and run through an inside wall?
 
  #11  
Old 10-21-13, 06:48 PM
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can service entrance wire be used and run through an inside wall?
If you mean service entrance cable, yes, it can be used. You would want to use SE Type R commonly referred to as SER cable with three insulated conductors and one bare grounding conductor. It can be commonly found with aluminum conductors in stock at supply houses, but copper SER cable usually has to be ordered.
 
  #12  
Old 11-16-13, 09:37 AM
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Ready to hook up these feed wires. A question: Should I try to create a strain loop before going into the lugs?

You see in this picture a small loop for the grounds. My thinking is that if we have slip joints for frost/ground heave, then there should be some available wire to go with the expansion. But if I try this on the larger wire its going to look messy. Second picture is the larger wire where I could go up and then bend back down - not a full loop, but something at least.

Before I cut these I want to be sure. The first choice is to just come straight out of the conduit and connect directly to the lugs - which would be pretty straightforward.





 
  #13  
Old 11-16-13, 11:44 AM
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For the ground rod connections I just used a clamp around the ground rod. Did keep it a continuous wire from the one rod to the next, and also put some No-Ox on it.



 
  #14  
Old 11-16-13, 07:03 PM
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Second picture is the larger wire where I could go up and then bend back down - not a full loop, but something at least.
There are three double barrel lugs to feed power into the meter socket, you feed all 3 sets of lugs from the bottom. You do not go up and bend back down.

Ready to hook up these feed wires. A question: Should I try to create a strain loop before going into the lugs?
Nope, not necessary. Why didn't the utility company terminate these wires? Normally the utility company furnishes and installs the power to the meter, but if this is an overhead service area, you may have to furnish and install your own power conductors underground to the meter socket, if you want optional underground service.

Before I cut these I want to be sure. The first choice is to just come straight out of the conduit and connect directly to the lugs - which would be pretty straightforward.
I would take each conductor directly to the lugs on the left 200 amp breaker. Remember, you don't want to waste space as you probably will eventually have a 2nd set of 200 amp feeders coming into this section too.

How long is the ground rod, do you have 8 feet minimum rod in the ground? Where does the ground wire go after it loops through the ground rod clamp? What size is the ground wire?
 
  #15  
Old 11-17-13, 04:59 AM
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Thanks Joe, I will skip the strain relief and just come straight into the lugs.

This is a project I have been doing myself - pulling it all the way to the transformer (which required having the electric company unlock the transformer). Its been a big project (and a lengthy one), including a complete overhaul of the house main panel. But getting to the final steps.

Indeed there will be another set coming out of the breakers, so any space I can save is great.

The ground rods are another story. This is all ledge (granite a lot of it). I pounded the snot out of them (a technical term I know). Considered going in at an angle instead, but got them within a couple feet of ground level and will let the inspector tell me what he prefers (I tried 12 different ground rod locations all around this building and no go on any of them).

The grounds are 4 ga copper. The panel is using braided (no sheath) - the run to the house side is stranded. They run from the farthest rod (over 8ft apart) to the near rod - no splicing - then to the panel.
 
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Old 11-17-13, 07:14 AM
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Considered going in at an angle instead, but got them within a couple feet of ground level and will let the inspector tell me what he prefers (I tried 12 different ground rod locations all around this building and no go on any of them).
You also have the option of digging a trench and laying the rod in horizontally. The NEC gives a minimum depth of the trench, but I am not sure what it is without looking it up. I suspect the inspector may not like the short rod in the ground, but that is up to them.

The grounds are 4 ga copper.
The ground to a rod doesn't have to be any larger than a #6, but #4 is OK. As I recall, this service is on an outbuilding with no water service.
 
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Old 11-17-13, 08:13 AM
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You also have the option of digging a trench and laying the rod in horizontally. The NEC gives a minimum depth of the trench, but I am not sure what it is without looking it up. I suspect the inspector may not like the short rod in the ground, but that is up to them.
Good to know. On one of them, the portion that was sticking up I bent over into a trench (it might not be deep enough, will look it up). Neither rod was cut. The one sticks up about 18". Im perfectly happy to do them in some other way, but need the direction from the inspector (in my town they dont like giving direction up front - saying its not their job to 'design' it. So I just need to do the best I can figure out, and then redo if they take exception to something. Not the way I would like to work, but hey, its on me to adapt to their way of working)


The ground to a rod doesn't have to be any larger than a #6, but #4 is OK. As I recall, this service is on an outbuilding with no water service.
Correct, an outbuilding with no water. On the house panel I ran a #4 to the water main inlet from the panel ground. A PITA, because it was on the complete opposite diagnal side of the house. But its done.

Thanks for all the insights. After your post, Im contemplating calling and asking the electric company if they want to do the hookups to the meter - at the same time as the street hookup. There is some logic there that they would own everything up to the meter, although I did lay the underground and pulled the wire. Would only take a few minutes, and I can go either way they prefer.

Thanks for all the great questions/insights.

(ps: just looked it up and ground rods can be layed in a horizontal trench 30" deep)
 
  #18  
Old 11-17-13, 10:02 AM
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It would take some pre bending, but you could use SER in the wall and into the inside panel.
 
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Old 11-17-13, 01:44 PM
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Did the hookups. Wanted the outgoing on the breaker to the right, simply because thats the side the house is on so natural to expect to use the breaker on that side - and want to use that knockout straight out the back to feed into the out building directly.





 
  #20  
Old 11-17-13, 02:34 PM
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There is some logic there that they would own everything up to the meter, although I did lay the underground and pulled the wire.
I seriously doubt the power company will ever take ownership and responsibility for the underground conduit/wire you installed, but they may. No two power companies are exactly alike. Did you use antioxidant on your aluminum wire terminations?
 
  #21  
Old 11-17-13, 03:48 PM
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Did use antioxidant on all the connections, including the ground to ground rods.

Time to call for inspection, will post an update on what doesnt pass.
 
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Old 11-17-13, 03:52 PM
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Antioxidant paste , while a good practice, is not required.
 
  #23  
Old 12-26-13, 11:20 AM
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OK - the primary hookups all inspected and passed and power company connection appointment scheduled.

Now.... onto the next step of connecting to the shed. Inside the shed is standard 2/4 construction. It has a 100A panel.

So I will go through the main panel seen in the pictures - out the back and into the inside wall. then it needs to go through one stud before entering the inside panel. Since its going through a wall stud, I want to have the smallest hole that is needed.

My first thought was that it needs to be sized for the outside breaker - 200A - until it gets to the inside 100A panel. However, one electrician told me there is a section of code that would allow the wire to be sized for the inside panel (because its within 3 feet of each other... or something like this?)

Keeping the wire as small as possible will reduce the hole size in the stud.

If I could just pull copper service entrance (SER, or SE Type R as suggested) it would be great. For 100A the wire size could be #4 Cu. For 200A it would be 2/0 Cu (?) which would be quite a bit larger, so you see the motivation to keeping it to the smaller size.

Welcome any insights on whether trying to go to this smaller wire size is doable per code??
 
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Old 12-26-13, 01:25 PM
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Your electrician is referring to the "tap" rules but I don't know if they would apply in this situation.
 
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Old 12-26-13, 06:28 PM
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Your electrician is referring to the "tap" rules but I don't know if they would apply in this situation.
Good point, Furd. I don't believe any of the tap rules apply. Generally tap rules could apply if this new conductor were tapping a 200 amp feeder conductor, but that isn't the case. In this situation this new conductor terminates right at the circuit breaker. I believe the choices are 1.) Change the breaker to 100 amps OR 2.) Install a 200 amp rated feeder. I am almost sure the breaker cannot be changed because of the frame size. Here is a better explanation of the tap rules.

Understanding the Rules for Feeder Taps | Code Basics content from Electrical Construction & Maintenance (EC&M) Magazine
 
  #26  
Old 12-27-13, 05:52 AM
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Thanks guys, and exactly why I love this forum. Appreciate the link.

For 200A then its looking like 2/0 Cu SE-R

(or individual cuts pulled through conduit, still the preferred).

This electrical code stuff is fascinating. I hear so many different opinions and interpretations, even between the electrician and the inspector (and power company engineer for that matter!). And although I need to pass inspection - the inspection is really just a means to an end to ensure its safe (nothing is ever 100%). Then certain electricians like to talk mumbo jumbo to scare the customer into just letting them do whatever they want (I had one guy that did this - and my take was he just wanted me to stop asking questions about what he was doing). And others really didnt know any more than I did - maybe were just going to go ask someone else.

Without being able to educate myself I have no way of sorting through good advice from bad.

Thanks again! So far Im quite pleased with a very nice upgrade and clean install - maybe a little overkill, but I dont mind that at all.

 
  #27  
Old 01-08-14, 06:34 PM
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The inspection passed.

The hookup was made at the street.

New 200A panel to the house wired.

Throw the breaker and, wala! Im live on the new system. Im pretty sure the lights in the house are brighter now......

 
  #28  
Old 01-08-14, 06:37 PM
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.......................................
 
  #29  
Old 01-08-14, 06:56 PM
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Congrats. .
 
  #30  
Old 02-17-14, 01:12 PM
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Phase II

OK, the house is wired, inspected, and all is good.

I decided to run the shop subpanel via conduit on the inside wall. It meant cutting out a stud and putting in a header. A little more work, but its better in the conduit.



The main breaker is a 200A and the breaker panel is a 100A main. I ran 2/0 Cu from the main breaker to the panel.

And a ground.

But here is where I get confused. The ground comes in and connects to the chassis of the breaker panel. The neutral to the neutral bus, and two hot ones. I get that.

But all my 220V shop equipment only has three wires. And I pulled 10/2 (two conductors and ground) to all the outlets.

So normally I would hook this 220 up as two hots, and the ground going to the neutral bus. But my neutral, and my ground are isolated from each other. For the 110V I get it - black to hot, white to neutral, ground to ground.

Do I need to redo all the 220 pulls to 3 wire? (plus ground). My house certainly isnt this way.

And if some 220 grounds going to the neutral, and some 110 runs having a bare wire going to ground, its pretty easy for these to touch thus grounding the neutral bus.

What am I missing?
 
  #31  
Old 02-17-14, 01:26 PM
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But all my 220V shop equipment only has three wires. And I pulled 10/2 (two conductors and ground) to all the outlets.
That is correct for 240 (you don't have 220). Note 10-2 is only good for 30 amps maximum.
all my 220V shop equipment only has three wires
Really 2 conductors and a ground for 240.
So normally I would hook this 220 up as two hots, and the ground going to the neutral bus. But my neutral, and my ground are isolated from each other.
Yes, because you have a subpanel.
Do I need to redo all the 220 pulls to 3 wire? (plus ground).
No, 240 uses two hots and a ground. No neutral is used.
And if some 220 grounds going to the neutral,
That is wrong in a subpanel. All ground must go to the ground bar and neutral only to the neutral bar. Correct any that are in the wrong place.
my neutral, and my ground are isolated from each other
The ground should be bonded to the panel housing. The neutral should be isolated from the panel housing. Is that what you have?
 
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Old 02-17-14, 01:27 PM
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Many panels require an ground bar to be added. Can't see if yuor panel has one.

Straight 240 is two hots and a ground.

The grounds should not touch the neutral bar.

The cover of the LB needs to stay accessible.
 
  #33  
Old 02-17-14, 02:01 PM
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Thanks for the replies, and sorry for my poor terminology (yes, it matters I know)

I have 240.

I did install a ground bar to the panel. In fact I added one on each side just to make it easy to route the wires.

The neutral is isolated from the ground. (had a jumper that needed removed.

It sounds like all I need to do for the 240V is two hots to the breaker, and then the bare wire to the ground bar (NOT the neutral). Thank you for this clarification. Yes 30amp (10/2). (and the white wire should be made red or black where exposed).



"The cover of the LB needs to stay accessible"

I would have missed this - will put an opening in the paneling to accommodate it.

Thanks again - will try to get a pic of the panel posted...
 
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Old 02-17-14, 02:42 PM
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You have it. Good luck on the rest of the project.
 
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Old 02-21-14, 03:25 PM
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Yet another question:

Is there any reason I can't put the ground bus bars horizontally across the top and bottom?

Normally I see them vertically along side the neutral bar. Was thinking if I put it across the top and bottom I could attach grounds first and it would be neater then when running the neutrals/hots down the sides.
 
  #36  
Old 02-21-14, 04:33 PM
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Depends where the holes for the ground bar are in the panel. Most panels come pre-tapped.
 
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