stupid sub panel question?

[rust bucket bronco]

I am wanting to bring a 90 amp service to my 30x48 shop and am having questions on the sub panel. First off I can't find a 90 amp sub panel for the shop, do they exist? I have the 90 amp breaker for the house and enough #2 aluminum wire for the run to the shop, that were given to me. Does any one know were I could get a 90 amp sub panel? I would like to run a square d homeline if possible since that is what I have in the house. I went to one of the big box stores and found 60, 70, 100, and 125 amp sub panels but no 90 amp.

[TRDon]

buy the 100 or the 125 for that matter. A panel's rating is only what it is fused at. I have run so many 60 amp sub panels using 125 amp panels just for the extra spaces alone beyond the fact that you can get a main lug only panel for about $30 with 20 spaces in it. For that kind of space and availability, why not go that route?

So in conclusion, buy a 100 or 125 with the spaces available to suit your needs and you can fuse it at 90 and you automatically have a "90A Sub-panel" :)

[rust bucket bronco]

I didn't know the main breaker on the sub panel was replaceable. If thats the case I'll go with the 100 amp sub panel it had a total of about 24 spaces on it. Thanks

[Torque1st]

You want a sub panel with a main breaker anyway to use as a disconnect. The size of the main breaker in the sub panel does not matter to the feeder wire. The breaker in the main panel protects the feeder wire.

[2LTim]

Correction:
You have 4 possible disconnect points, depending on which one has the lowest current carrying capability; The main breaker in the house panel. The breaker in the house panel that goes to the garage. The wire that goes to the garage. And last but not least, (If you use one) The breaker in the sub panel.
The "Weakest Link" determines the amperage capacity in your sub panel and system. If you have a 100 amp breaker in the house and a 100 amp main breaker in your sub panel, and #10 wires connecting the two panels, you have a 30 amp sub panel, like it or not!
I agree with TRDon, why spend the extra $30 or so to have a "Main" breaker in a sub panel. If you want to "Disconnect" the power to the garage, just go in the house and turn off the breaker. I have been in my home for ten years now, and can't think of a single instance where I needed to cut all of the power to the garage.
That's my two cents worth,
Tim

[rust bucket bronco]

I was assuming that a detached garage had to have a main breaker in the sub panel. Guess I have another question for the inspector on mon.

[Aceman]

I agree with TRDon, why spend the extra $30 or so to have a "Main" breaker in a sub panel.

The code requires a disconnect.

[sberry]

Yes, the only way to not have a main is to have a panel with 6 spaces or less, too few to really split a lot of tool circuits.

[MisterCMK]

buy the 100 or the 125 for that matter. A panel's rating is only what it is fused at. I have run so many 60 amp sub panels using 125 amp panels just for the extra spaces alone beyond the fact that you can get a main lug only panel for about $30 with 20 spaces in it. For that kind of space and availability, why not go that route?

So in conclusion, buy a 100 or 125 with the spaces available to suit your needs and you can fuse it at 90 and you automatically have a "90A Sub-panel" :)

TRdizzle, is that you?

[sberry]

Guess I have another question for the inspector on mon. No need to question him here,,, if the panel has more than 6 spaces you need a main.

[rust bucket bronco]

thanks guys, i'm sure i'll have more questions once i get into the meat and potatoes of the wiring.

[Torque1st]

The disconnect is for your own safety and for anyone else that might work on the sub panel. If your disconnect is the main panel breaker you might turn that breaker OFF. Then go to work on your sub. In the meantime a kid or the wife pops another breaker then goes to the main and starts flipping breakers that are OFF back ON. -ZAP!!!!! -You are toast! That is why there are line-of-sight rules etc.

[TRDon]

No need to question him here,,, if the panel has more than 6 spaces you need a main.

Are you sure that isnt a local code? I have installed and had inspected quite a few MLO panels in garages where the disconnect is the breaker in the main panel feeding it. I havent needed a disconnect in my area. I also cannot find anything in the 2008NEC about such requirement of disconnect for a garage either :confused:

Bottom line, make your life easy and ask your local inspector how he wants it done. He is the athority having jurisdiction in your town for this so if he wants it, give it to him :) Im just saying make a 3 minute phone call or question and potentially save yourself $30 in the process.

CMK- SN95 5.0 > * :bounce:

[TRDon]

The code requires a disconnect.

In the NEC? Reference number? I cant seem to find it. If so, it hasnt been enforced in my area.

Edit: I just realized that this is probably not an attached building. If there is more than one circuit going to it, than these guys are correct, you will need a disconnect for that building. For that, you can either run a main breaker panel and use that as a disconnect or use the MLO panel and feed the panle via installed breaker.

Upon realizing this, I tried to look it up but I still cant find it. If you have the reference for me that would be greatly appreciated :)

[dwilliams35]

The 2005 code was fairly clear that you could just use the breaker in the main panel as the disconnecting means for a subpanel: they changed some language in the 2008 to say something down the lines that it "shall be inside the panel oir ahead of the panel on the feeders". Now just what the heck that means, I don't know: (I don't have the book with me at the moment, so I'm just winging this from memory). Sounds to me like you could use the second part of that and just use a Main-lug panel no problem just like you could before. Of course, it's going to be up to any local inspector's interpretation.

[Aceman]

In the NEC? Reference number? I cant seem to find it. If so, it hasnt been enforced in my area.

Upon realizing this, I tried to look it up but I still cant find it. If you have the reference for me that would be greatly appreciated :)
Here's a few:
225.31
225.32
225.33
225.36

The 2005 code was fairly clear that you could just use the breaker in the main panel as the disconnecting means for a subpanel: they changed some language in the 2008 to say something down the lines that it "shall be inside the panel oir ahead of the panel on the feeders". Now just what the heck that means, I don't know: (I don't have the book with me at the moment, so I'm just winging this from memory). Sounds to me like you could use the second part of that and just use a Main-lug panel no problem just like you could before. Of course, it's going to be up to any local inspector's interpretation.
Where are you getting your information?

It was the same in 05 as 08, no changes were made. Aside from a local amendment not requiring it, the code says you need a disconnect in a detached building.

[dwilliams35]

Where are you getting your information?

It was the same in 05 as 08, no changes were made. Aside from a local amendment not requiring it, the code says you need a disconnect in a detached building. Well, like I said, I don't have it in front of me, so I can't quote chapter and verse, but I sat there at my desk with both years' code books for a couple of hours last week trying to decide whether I needed to buy the extra ten grand worth of main breakers or not: It's in there somewhere, with the nifty gray highlighting for when they change something between code editions.

[TRDon]

Here's a few:

225.32



Those were exactly what I was looking for, Thanks :) That would explain why it hasnt been a problem for me with attached garages, it isnt considered a seperate building and doesnt require a disconnect. It now seems that all buildings regardless of circuitry require a disconnect according to that article.

[Torque1st]

The Code is a minimum and does not cover everything. For my own safety and that of anyone else working on the equipment, if the power source is not within line-of-sight and near enough for me to shout I always provide a disconnect. My life and that of others is worth more than a few bucks saved.

[nissan_crawler]

The Code is a minimum and does not cover everything. For my own safety and that of anyone else working on the equipment, if the power source is not within line-of-sight and near enough for me to shout I always provide a disconnect. My life and that of others is worth more than a few bucks saved.

I'm with you on that one. Is it worth saving $50 to fry somebody? Even the lock down, tag out procedure isn't enough sometimes. I've seen people do some real bonehead stuff.

[checkthisout]

The Code is a minimum and does not cover everything. For my own safety and that of anyone else working on the equipment, if the power source is not within line-of-sight and near enough for me to shout I always provide a disconnect. My life and that of others is worth more than a few bucks saved.

I agree. It just makes sense too.

Not having a Main Breaker in a detached building's breaker panel is akin to having one in the detached building but not one in the house's Main Panel.

[sberry]

Not having a Main Breaker in a detached building's breaker panel is akin to having one in the detached building but not one in the house's Main Panel. You need a breaker in the main panel, simple as that and you need one in a detached building if there is more than 6 spaces in the panel. There is a bunch of logic not requiring one in an attached building (lengthy) but one reason it encourages turning off the main panel breaker completely de-energizing the panel for work. Even a single circuit to a shed requires a disconnecting means, simple switch may do.
As for code version changes and local amendments there will be very little variation in regards to this aspect. Many places are doing away with local amendments in most applications, I heard even NYC is going to adopt NEC? Most are concerned with methods and some supplementary ground issues, etc. You wont find a problem if you follow Aceman here, he has just been thru code study and current testing, probably as familiar with these issues and changes as most inspectors, more than some.

[TRDon]

You need a breaker in the main panel, simple as that and you need one in a detached building if there is more than 6 spaces in the panel. There is a bunch of logic not requiring one in an attached building (lengthy) but one reason it encourages turning off the main panel breaker completely de-energizing the panel for work. Even a single circuit to a shed requires a disconnecting means, simple switch may do.
As for code version changes and local amendments there will be very little variation in regards to this aspect. Many places are doing away with local amendments in most applications, I heard even NYC is going to adopt NEC? Most are concerned with methods and some supplementary ground issues, etc. You wont find a problem if you follow Aceman here, he has just been thru code study and current testing, probably as familiar with these issues and changes as most inspectors, more than some.

I didnt find anything in the code about a single circuit or 6+ breakers anywhere. I just read that if a seperate building (from the main service) is fed with any circuitry, all ungrounded conductors need to have a disconnect wether it be a breaker or a switch or series of switches. The way I interpret that is that any seperate building being fed requires a disconnecting means for all ungrounded conductors regardless of quantity.

I just want to know so I can have it correct in the future. :)

[sberry]

I would have to look up the exact wording, but,,, for service entrance a 6 space panel doesn't even require a main, same for a garage, they call it "one throw of the hand" However,, these days 6 spaces isn't much.

[Aceman]

I didnt find anything in the code about a single circuit or 6+ breakers anywhere. I just read that if a seperate building (from the main service) is fed with any circuitry, all ungrounded conductors need to have a disconnect wether it be a breaker or a switch or series of switches. The way I interpret that is that any seperate building being fed requires a disconnecting means for all ungrounded conductors regardless of quantity.

If you read part II of article 225 it covers it. Here's where it gets a little tricky, the disconnecting means at a garage for a feeder needs to be service rated. If you run a little branch circuit out there this doesn't apply. All main breaker panels as far as I know are service rated, it's easy to check though, just flip the panel door open and read the writing on the inside of the cover. It'll usually say "suitable for use as service equipment." On the other hand, if you buy a six space main lug panel, and try and use the six handle rule instead of buying a main breaker panel, make sure the panel door instructions allow it to be used as service equipment that way. As far as I know, there are no panels that allow it and is why I always recommend a main breaker. Besides can anyone really get away with only six spaces anymore?

[Junkman]

If you read part II of article 225 it covers it. Here's where it gets a little tricky, the disconnecting means at a garage for a feeder needs to be service rated. If you run a little branch circuit out there this doesn't apply. All main breaker panels as far as I know are service rated, it's easy to check though, just flip the panel door open and read the writing on the inside of the cover. It'll usually say "suitable for use as service equipment." On the other hand, if you buy a six space main lug panel, and try and use the six handle rule instead of buying a main breaker panel, make sure the panel door instructions allow it to be used as service equipment that way. As far as I know, there are no panels that allow it and is why I always recommend a main breaker. Besides can anyone really get away with only six spaces anymore?

My wife takes 6 spaces just to land her broom!!!!:lol_hitti

[sberry]

I believe the 6 space panels are service rated, seems I read it on one the other day. Like you said, one should look but I used one on an entrance a while back. Even some of those little 2 space units list service I believe.
I certainly agree that amount of spaces isn't enough by modern standards especially with so much specialized equipment, with a piece like a chop saw for example I like a dedicated circuit.

[Torque1st]

Be safe, regardless of what minimum standard is specified by "The Code" and always provide a line-of-site disconnect for any electrical panel or device.

Once a person has been "buzzed" a few times they get a little anal about it. I have been "buzzed" by the wife while working on a ceiling fixture when she forgot I was doing it then walked in and threw the light switch.

[TRDon]

If you read part II of article 225 it covers it. Here's where it gets a little tricky, the disconnecting means at a garage for a feeder needs to be service rated. If you run a little branch circuit out there this doesn't apply. All main breaker panels as far as I know are service rated, it's easy to check though, just flip the panel door open and read the writing on the inside of the cover. It'll usually say "suitable for use as service equipment." On the other hand, if you buy a six space main lug panel, and try and use the six handle rule instead of buying a main breaker panel, make sure the panel door instructions allow it to be used as service equipment that way. As far as I know, there are no panels that allow it and is why I always recommend a main breaker. Besides can anyone really get away with only six spaces anymore?

Does a 60 amp branch circuit apply or are you just talking a 15 or 20 amp. I am just curious because at that point, whatever comes from the main panel after a braker is considered a branch circuit.:shocking: This is getting sticky :confused: I think I am finding myself asking more questions about this the more get answered :(

[sberry]

For a single circuit a simple switch inside the door of the building would count as a disconnect means, again, if the building is detached it needs disconnecting method, if it is attached it does not. Look at it this way, you can run several circuits to an attached garage from the main service.
We get some argument here but as far as code is concerned a service to a detach garage is a service to that building,,, needs disconnect means as well as its own supplementary grounding system.

[sberry]

Copied from Bob Keis at code forum.
The panels in separate buildings are not really subpanels as far as code is concerned. They are the service equipment for the structure. You can have a subpanel from the service equipment in each building if you want. Between buildings, section 250.32 applies and if there are metal interconnections between buildings such as water piping, or air lines, or any metal interconnection at all, then you must install an equipment ground wire so if you have a 120/240 system, you would have four wires. The neutral would be separated in each building and a grounding bar would be installed, just like a subpanel. Then the code requires a grounding electrode conductor (GEC) to a grounding electrode (usually a ground rod). The GEC will be connected to the equipment ground bar at each building. This is not to clear overcurrent devices, this is for two reasons. One is lightning, the more important one is to put the equipment ground at the same relative potential as the earth. This is for step potential or touch potential voltages so that what you touch in the building is at the same potential as what you are standing on. Now the tricky part. If you do not have any interconnecting metal between buildings, the code allows you to install three conductors between buildings. When you do this you bond the neutral and ground the neutral just like a new service. Some inspectors think that every panel in a separate building must be treated as a subpanel, but this is not true. In past codes (1996 and older) these rule were in section 250-24 and Exception 2 addressed the grounding bus.

[TRDon]

I get what you are saying :) Thanks. Probably why it hasnt become an issue for me. I have only done 1 detached sub panel and if I remember correctly, I back fed a breaker for that one. I didnt do a seperate grounding for it though and I had that discussion with the inspector and he said that it was fine since I ran a ground back to the panel with my feed.

[TRDon]

Awesome explanation. You said you got that at a code forum? Do you have a general link to that so I can look over some code stuff and stay fresh on this. I dont dig into the code too often and I would like to stay sharp :)

[sberry]

I didnt do a seperate grounding for it though and I had that discussion with the inspector and he said that it was fine since I ran a ground back to the panel with my feed. It needs a rod even with ground wire unless its in the same building. I will get back with some code links later.

[sberry]

http://www.tchism.proboards49.com/index.cgi?board=general
http://forum.doityourself.com/electrical-c-d-c-9/
http://www.selfhelpandmore.com/home-wiring-usa/accessory-structures-to-dwellings/wiring-a-detached-garage-2002.php
The first one is not really a DIY forum but the second is good as they come across about every conceivable question and are good at explanations, the 3rd is specific page to garages and they do have a forum.

[vc-onthepc]

i just had a 200 amp service panel installed not a sub panel and not sure if this will help but in maryland it was required to have a service dissconect before the main breaker in the panel . .. it also required a seperate mouning location not on my building along with the electric meter . why you ask ?

it was not permantly attached to the ground i.e drop off garage ....

[TRDon]

i just had a 200 amp service panel installed not a sub panel and not sure if this will help but in maryland it was required to have a service dissconect before the main breaker in the panel

That is the same case here in MN, IF there is a pipe that carries the unfused conductors within the house longer than 3 feet. If the piping within a building is less than 3 feet, the main breaker can be used as the disconnect for the site.

[sberry]

Ace may help with this one but I dont think it actually mentions 3 ft anywhere, its called nearest point of entrance or something like that? The idea is that someone can figure out where its at at any rate.

[TRDon]

Ace may help with this one but I dont think it actually mentions 3 ft anywhere, its called nearest point of entrance or something like that? The idea is that someone can figure out where its at at any rate.

3 feet may be how it is interpreted here by all the local inspectors. It has been how it has been done here since I have been an apprentice. You do want to have the disconnect at the nearest point of entrance, but if your design does not allow your panel to be on the exterior wall at the point of entrance, than the fused disconnect can be either just inside, than pipe to the panel, or on the exterior with the meter.

[roger55]

The code requires a disconnect.

Where I live, if the sub is within 50 feet of the main, then the disconnect is not required.

[Torque1st]

...In past codes (1996 and older) these rule were in section 250-24 and Exception 2 addressed the grounding bus.
Just one reason I keep all my old copies of the code. Old copies can sometimes be picked up at public library book sales.

[sparky1562]

Copied from Bob Keis at code forum.
The panels in separate buildings are not really subpanels as far as code is concerned. They are the service equipment for the structure. You can have a subpanel from the service equipment in each building if you want. Between buildings, section 250.32 applies and if there are metal interconnections between buildings such as water piping, or air lines, or any metal interconnection at all, then you must install an equipment ground wire so if you have a 120/240 system, you would have four wires. The neutral would be separated in each building and a grounding bar would be installed, just like a subpanel. Then the code requires a grounding electrode conductor (GEC) to a grounding electrode (usually a ground rod). The GEC will be connected to the equipment ground bar at each building. This is not to clear overcurrent devices, this is for two reasons. One is lightning, the more important one is to put the equipment ground at the same relative potential as the earth. This is for step potential or touch potential voltages so that what you touch in the building is at the same potential as what you are standing on. Now the tricky part. If you do not have any interconnecting metal between buildings, the code allows you to install three conductors between buildings. When you do this you bond the neutral and ground the neutral just like a new service. Some inspectors think that every panel in a separate building must be treated as a subpanel, but this is not true. In past codes (1996 and older) these rule were in section 250-24 and Exception 2 addressed the grounding bus.


This has been changed in the 2008 code. Now you have to pull the ground wire, not an option. That part about metal to metal connection always confused people. What about a pone line or Cable TV? I might go out on the NFPA web site and see why they changed it.

On edit: here are the comments, page 70-193
http://www.nfpa.org/assets/files/PDF/ROP/NEC2008Article250-280.pdf

[sberry]

I believe it includes phones or cable, says ANY metal. I agree, in todays world it only makes sense to use 4 wire.

[diveman52]

If this is a seperate building a main disconnect is required by the NEC. (National Electric Code)