if you feed the sub panel from a breaker in the main that breaker counts as the disconect.
as for seperating the ground and netural usually you can unscrew a bar conecting the two at the bottom of each.

I bought a main breaker Cutler Hammer panel today, and exactly as you said it has an S-shaped metal strap attaching the right hand neutral bus to the metal case with a green bolt. I'll take it off.

I'll replace the 100 amp breaker with a 60 amp one.

One more question: I'll be running #6 wire in conduit with a bottom feed. There's space between the metal shield covering the always hot top part of the panel, which I assume is for gaining access to that part of the panel, then loop each wire 180 deg to attach to the main breaker/neutral bus/ ground bar, attachment points for each are under the shield. This is only way I can see using a bottom feed. Am I correct?

Yes, you can bring the wires in at the bottom and then loop them back down to connect to the lugs at the top. With #6 wire this will be very easy for you to do and there will be plenty of room to make some nice gradual bends.

You could also install the panel with the main at the bottom and then your connection points are right there where the feed comes in. As far as I know all of the newer CH main panels can be installed either way. If your main breaker moves side to side - then the panel can be mounted with the main at either the top or bottom.

One last thing - if your panel came with a 100 amp breaker already installed just leave it in place as is. Get a 60 amp breaker and install it at the panel you are feeding the new one from.

Two more excellent points!

The instructions with the panel do say it can be mounted vertically, inverted, or horizontal.

So if I feed this subpanel from my service panel with a 60 amp breaker/#6 wire, I can leave the 100 amp breaker as a disconnect? Never thought of that. Thanks! It saves me the cost of another 60 amp breaker.

This main breaker panel was less than $20 more than a main lugs CH 12 circuit panel, so it's absolutely worth it for the convenience of having a shut off in the garage if nothing else.

My dear departed dad was a POCO high voltage cableman, and I know my questions would have been kids stuff for him. But I'm always amazed at the excellent information and advice I get on this forum. I really appreciate it. Thanks again!

Your dear departed dad worked with a totally different set of rules than you need to now.

I know a guy who does that sort of work. He lives in a cabin in the woods, his power source is a rack of forklift batteries, which he has rigged up in such a way that it randomly shorts out at various inopportune times, shooting monster sparks across the livingroom and scaring the living bejeezus out of his poor girlfriend.

I've been meaning to get up there and straighten out his wiring for quite some time...

You'll never see me climbing a pole, nor will I ever be recommending my friend to wire someone's house. Leave the outdoor pole stuff to the linemen and the indoor stuff to the electricians. There IS a big difference :)

"his power source is a rack of forklift batteries, which he has rigged up in such a way that it randomly shorts out at various inopportune times, shooting monster sparks across the livingroom and scaring the living bejeezus out of his poor girlfriend."

ROFLMAO!

Point taken.

I am about to do the same thing (if I can) -- buy a 100-amp main breaker panel and use it as a subpanel that is fed from a 60-amp breaker in the original main panel. The wiring from the original main panel to the new subpanel is #6 wire.

jmvd20 wrote,

"One last thing - if your panel came with a 100 amp breaker already installed just leave it in place as is. Get a 60 amp breaker and install it at the panel you are feeding the new one from."

So, do I understand this correctly? -- I can leave a 100-amp main breaker in the new main breaker panel that I am going to use as the subpanel? I assume the #6 wire is protected by the 60-amp breaker in the original main panel and that's why it's okay to leave the 100-amp main breaker in the new panel?

Thanks.

Exactly. The 100 will simply be a disconnect, and the 60 will properly protect the feeder.

As was stated earlier in this thread, a sub-panel within the same structure as the main does NOT need a disconnect or main breaker. The feeder breaker serves this purpose.

Thanks.

While looking at 100-amp main breaker panels, I noticed that the specs all state the minimum and maximum wire size -- and they all say that the minimum wire size is #4. Since I will be using this main breaker panel as a sub-panel, I will actually have #6 wire coming into it. I assume that is okay, and that the only reason that they state a minimum wire size of #4 is for when it is being used as a main breaker panel rather than as a sub-panel. Is that correct?

That can't be right for a 100A panel. I know for fact that those terminals can typically accept down to #8 and sometimes #10.

Same here, I am not sure where the #4 is coming from - I have installed numerous 100 amp main panels as subs and used #6 to feed them.

Okay thanks. It makes sense to me that the smaller size wire would still be able to be connected to the main panel being used as a sub-panel. I just thought I'd double check since when I read the specs for the 100-amps panels online they talk about minimum wire sizes.

Sorry, I now need more help.

I just bought a Siemens 100 Amp Main Breaker Panel (Model G1224B1100cu) that I will be using as a subpanel. I can't figure out what to do in terms of the neutral bar and grounding bar. The so-called "instructions" are very brief, very vague, and confusing to me. There is a vertical bar with connecting screws on each side. The one on the right has a big green screw near the top that is attached to a metal clip which also has a large connecting set screw for connecting a wire to it. I assume that I am supposed to connect the incoming neutral wire to that set screw. The bar on the left has no green screw and no set screw. There is also a jumper bar that goes across and connects the two vertical bars.

I assume that since I am going to be using this main breaker panel as a subpanel, I have to figure out away to have a neutral bar that is not connected (bonded) to the metal panel box itself, and I also have to figure out a way to have a grounding bar that IS connected (bonded) to the metal panel box.

How do I do this? If the neutral bar on the right is not supposed to be bonded to the metal panel box, I guess that menas that I connect the incoming white wire to the big set screw on that bar and I do NOT tighten the big green screw so that bar on the right will NOT be bonded to the panel box.

Do I then remove the bar going across that connects the two vertical bars, and then figure out a way to bond the vertical bar on the left to the metal panel box and use that as the grounding bar? If so, how do I bond that bar on the left to the box? If I take the big green screw and clip off of the vertical bar on the right to use it as a way to bond the bar on the left to the box, there is no way connect the white neutral wire to the neutral bar on the right.

Would another option be to: 1) leave everything as is; 2) leave the connecting bar in place that connects the two vertical bars and use them both as unbonded neutral bars; 3) NOT tighten the existng big green screw so that neither vertical bar is bonded to the metal panel box; and then, 4) buy a separate grounding bar, bond it to the metal box, and use THAT as the grounding bar?

I'm going to answer my own post here.

I figured it out.

I left the neutral bars on the panel as is and I didn't bond them to the panel box. Then I bought two grounding bars and I added them to the panel box and they are bonded to the box. I bought and added a "Grounding Lug" and used that to bond the incoming bare ground wire to the box.

Personally, I think that it is unfortunate that Siemens provides so little information either with their product or on their website.

About the instructions issue. This type of thing usually does not come with instructions. In fact, I have seen some that did and was pissed to see it.
This type of stuff does NOT require "instructions". It is assumed that anyone buying such items knows what they are doing, or at least should before buying.

You can liken it to car parts. When was the last time you saw an alternator or fuel pump that came with instructions?

I'm adding a sub-panel to my main and bought a sub-panel. The sub-panel is set up to use as a sub with neutral and ground seperate and neutral insulated from the box. Buying a main panel means you have to do this seperation stuff yourself and instructions wouldn't cover a main as a sub.

The manufacturer makes both sub and main panels and wouldn't necessarily give instructions to change one into the other.

Depends on the manufacturer. If you order a SquareD panel, even in the main lugs only configuration you still have to buy an additional grounding bar.

I bought Cutler-Hammer to match the original box. Neutral bus and ground bus were installed seperately. It also included a pin to bond the case to neutral if needed, or you leave it out.

The two year later follow up :)

I just wanted to add a comment to the OP about using the same size breaker for the sub as the main. While it is correct that I am not aware of any NEC codes related directly to your SPECIFIC situation there is certain instances where that would be a problem. Its called "Selective Coordination" and mostly relates to health care systems and emergency/backups - Panels or breakers of importance if you will. So while it is not a code it is best practice to Selectively Coordinate your breakers so that the main does not trip but rather the sub trips first. Just wanted to add food for thought and to clarify in case someone see this thread as I did and thinks that its ok for all sub panels/breakers to be installed in such a mannor.

"it is best practice to Selectively Coordinate your breakers so that the main does not trip but rather the sub trips first. "

If you think by using the same rating that the local breaker will trip before the remote you are badly fooling yourself.
The breakers are there to protect the wiring, NOTHING ELSE.

Even two breakers of the exact same rating does not mean the local breaker will trip before the remote.

There is a rather wide tolerance on the trip time of breakers, and the inverse time ones most commonly used are slightly worse than the more sensitive magnetic only breakers.

Brickeyee,
""""If you think by using the same rating that the local breaker will trip before the remote you are badly fooling yourself.
The breakers are there to protect the wiring, NOTHING ELSE. """"

I THINK YOU NEED TO RE-READ MY POST.
I never said anything about using the same size breaker or trip settings will gaurantee tripping the main first or sub first. If you use the same size then yes depending on the different characteristics one will trip before the other. If you understand selective coordination then you will understand that if done correctly it is designed to prevent for example the main tripping before lets say the secondary panel. Whether it is done through trip settings or different size breakers/fuse/invertise time delay etc. This is done "selectively" to not only protect the wiring but prevent incorrect tripping where it would cause dangerous conditions.

That is fine if you have a simple overload where you're suddenly in between the ratings of the breakers, but with a substantial overcurrent (like a dead short), it's pretty much a random shot which breaker will open first regardless of the ratings.

"Its called "Selective Coordination" and mostly relates to health care systems and emergency/backups"

This is not a site thast deals with "health care systems and emergency/backups" it deals pretty much exclusively with residential wiring.

ronnatalie has it correct.

A significant short is going to have many thousands of amps flowing nearly instantly, and all the "selective coordination" is not going to ensure one breaker goes before another, no matter what there nominal ratings are.

The high current tripping of most breakers is in the magnetic portion of the mechanism, and while it is much faster than the thermal portion, it still has a lot of tolerance in the allowed response time.

The time is pretty independent of rating and is limited by the mechanical operation of the mechanism (and that adds tolerance on top of the tolerance in the electrical portion of the device).

One day on a job, one of my guys goofed making up a box for a 15 amp multi-wire circuit. Instead of connecting the red to the black of the outgoing circuit, it got mixed up with the black wire of in the incoming 14/3. Turning on the 15 amp circuit breaker caused the 200 amp main breaker to open. I was a bit baffled for a few seconds before investigating the junction. Then of course the two of them that worked on that particular junction pointed fingers at each other. Neither of them work for me any more hah, not that that incident contributed to it...

It�s called "Selective Coordination" and mostly relates to health care systems and emergency/backups"
This is not a site that deals with "health care systems and emergency/backups" it deals pretty much exclusively with residential wiring.

I agree, but the selective coordination theory still applies (at heart)

""A significant short is going to have many thousands of amps flowing nearly instantly, and all the "selective coordination" is not going to ensure one breaker goes before another, no matter what there nominal ratings are. ""

Absolutely Incorrect- I�m not sure you fully understand what selective coordination is.....

Google Selective coordination study.

When done properly all the variables are taken into consideration to "ensure" that one will open before the other. Now without doing such a study since it is just a residential panel and a homeowner you still should in best practice would like to have a breaker lower then the main rating and in MOST cases (not all) without doing the study the lower breaker will open before the higher breaker. Obviously again there are certain conditions where this may not be the case, but 99% of the time on RESIDENTIAL panels this holds true if they are the same brand/type breakers with similar characteristics but one is lower then the other.

Definition of Selective Coordination
"THE ACT OF
ISOLATING A FAULTED CIRCUIT FROM THE REMAINDER OF
THE ELECTRICAL SYSTEM, THEREBY ELIMINATING UNNECESSARY
POWER OUTAGES. THE FAULTED CIRCUIT IS ISOLATED
BY THE SELECTIVE OPERATION OF ONLY THAT OVERCURRENT
PROTECTIVE DEVICE CLOSEST TO THE OVERCURRENT
CONDITION."

-Tony
Licensed Electrician & Engineer

Here is a link that might be useful: Reading up link

I stand by my original statement, the premise provided that expecting a 100A breaker to trip before a 200A breaker when faced with a dead short is not going to be reliable. It's not even going to raise to your level of "USUALLY."

"Selective coordination" is NOT going to determine what breaker trips firs under fault conditions.

It may be useful for OVERLOAD conditions were a lower rated breaker could be expected to trip before a higher one, but that is relying on the thermal trip mechanism (and it has generous tolerances also, like many minutes at smaller (say 150%) overload (intended to allow starting surges in equipment to NOT trip the breaker).

For fault conditions there is NO WAY to predict what breaker in a cascade is going to trip.
The idea that a 20 ampo breaker WILL trip before a 100 amp breaker under fault conditions is WRONG.
There is NO WAY to predict the breaker that will open first.
Besides the breaker tolerances, things like wiring inductance will come into play in how fast a fault current builds up.

The whole thing sounds like an academic exercise with little connection to reality.

Overload is NOT the same as FAULT behavior.

If you want overload coordination that is achievable if you watch the breaker tolerances and ratings carefully.
The upstream breaker must be selected to account for the tolerance (and mechanism) of overload tripping.

Fault behavior is NOT going to work the same way.

WOW!!!!

""""Selective coordination" is NOT going to determine what breaker trips firs under fault conditions.""""

I guess you need to call up Square D and tell them to stop making adjustment pots on their breakers and spec charts. There are time delay adjustments to prevent such..... See the link below. This covers FAULTS not just overloads.

Excerpt form square D
The ground-fault function is divided into pickup and delay components (see
Figure 4). The pickup portion determines at what point the circuit breaker will
begin detecting a ground fault. The delay adjustment determines how long the
circuit breaker will delay tripping after a ground-fault has been detected. It is
supplied with both an "I�t IN" and an "I�t OUT" function on the LE, ME, NE, PE
and SE circuit breakers.

""""The whole thing sounds like an academic exercise with little connection to reality.""""

This is performed everyday in a lot of commercial and industrial applications (which have gardens :)) and it works. In fact most equipment of higher voltage will get a study performed to ensure safety upon start up. This hopefully will include an arc flash study my link below came from square d so it�s not just some little fairy making this up.

"""""I stand by my original statement, the premise provided that expecting a 100A breaker to trip before a 200A breaker when faced with a dead short is not going to be reliable. It's not even going to raise to your level of "USUALLY." """""

In normal conditions of residential panel in a garage you are going to deal with overload conditions (as well as faults). IE: too many electric heaters, lights battery chargers etc. So for this is why I say a lot of the time it isn't going to be a phase to phase short or a dead drop to ground. This DOESNT SAY IT (faults) DOESN'T or CAN'T HAPPEN(It happens at times too). Now in the event of a shorted wire or phase to phase short you have a more serous problem and which case yes the main may indeed open before the lower breaker or vise versa depending on the amount of amps and characteristics of everything combine. This is because in real life no one does a selective coordination study on a resi panel, but if you did do some research it is possible to pick out a set of breakers using the charts they provide where it will selectively open in BOTH conditions. Period!

Remember too that even if no study is performed does it hurt to at least have the breaker trip at the garage even if it�s just an overload condition?

Here is a link that might be useful: SQUARE D LINK

"I guess you need to call up Square D and tell them to stop making adjustment pots on their breakers and spec charts. There are time delay adjustments to prevent such..... See the link below. This covers FAULTS not just overloads. "

So you are going to fault the circuits and then adjust the breakers, then fault them again, then adjust the breakers.

Just because someone makes something does not mean it will operate as desired in the real world of the field.

The damage under fault conditions from delaying the trip time can be pretty extensive.
Fault currents can easily exceed 5,000 amps.

I have sen them blow holes in rigid metal conduit, even when the breaker was NOT adjustable.

The ensuing fire from the molten metal sprayed over the storage racks below only caused a few million in damage.

""""So you are going to fault the circuits and then adjust the breakers, then fault them again, then adjust the breakers. """"

Again and again, this is what the study does ---- it takes in account everything you have onsite and the conditions. They have specs that were tested in the lab and conditions to duplicate. Then a coordination study firm makes qualified decisions based on this data and other data and recommends the settings.
"""Just because someone makes something does not mean it will operate as desired in the real world of the field. """"

So you mean to tell me that when a company pays let�s say 7k to do a study this is just for fun? Are you going to trust the voltage rating on NM cable or go with the theory just because it�s designed for that doesn�t mean I can put that voltage to it???? Look things happen every day, and yes calculations get messed up or other factors change things but when a study is done correctly and I stress correctly it nearly eliminates all the guess work. What would you do if you were in an industrial environment that did the study, tell them to forget it and just randomly install breakers and settings any way you want?? Next time you visit a large industrial/commercial job look and see if the settings were just picked out of a hat or a study done. Imagine the hospital!

""""The damage under fault conditions from delaying the trip time can be pretty extensive.
Fault currents can easily exceed 5,000 amps. """""

This is why you need to look at a breakers AIC rating before just throwing it in. I have a 10K AIC in my hand now. This means that the breaker is design and tested to handle such. Maybe 1 in 50K or 75K will fail due to improper build and there is nothing you can do to prevent such

"""""I have seen them blow holes in rigid metal conduit, even when the breaker was NOT adjustable.
The ensuing fire from the molten metal sprayed over the storage racks be low only caused a few million in damage. """""

I don�t doubt you that this has happened as it does from time to time. We have all seen things like this being in the trade but I would be willing to bet 10-1 that the AIC rating was incorrect and/or no study was done or it was not installed correctly.

**See the link below for more information about another person asking about a study and should he do it himself**

Here is a link that might be useful: STUDY LINK

"Again and again, this is what the study does ---- it takes in account everything you have on site and the conditions. They have specs that were tested in the lab and conditions to duplicate."

unless you do the test with the actual wiring and fault it repeatedly to adjust everything it is NOT going to work.

This is a very application dependent item, not anything a lab can do for you.

Ever seen conductors move under fault current?

You should see power lines jumps.

It is the huge surge in the earths magnetic field, and the field form the return leg.

The wires jump very nicely. and occasionally a weak splice fails form the forces created.

We had to place concrete blocks over cables for fault testing to keep them from damaging terminations.

"""""Unless you do the test with the actual wiring and fault it repeatedly to adjust everything it is NOT going to work"""""

""""This is a very application dependent item, not anything a lab can do for you. """"

It�s like beating a dead horse.... This will be the last time I am going to try to explain this to you because I am not getting it through to you. I guess square D, engineering firms and hospitals do this kind of thing for fun and like to spend 7, 10 or 20K on things that don't work. You are only talking in opinion. Please provide your comments with some articles that a selective coordination study is bogus from a reputable source? You say you have seen all these issues but provide not details as to the specs or conditions it was under. It�s almost an insult and as if you�re saying the engineer who performs these studies is performing a job that serves no purpose. What else are you stating that can't be duplicated at a test site???? You can get the resistance of the wire, the temp, weather conditions, motor torques, load, time ran, splice types, terminations, age etc. During the study the engineer should get plans that show your entire setup. If there is something odd then they will review that and take it further into consideration. If someone doesn't do a spice correctly that is an incorrect installation, but if you take into account the available AIC at the site and spec your breaker correctly it will open without damage. The amount of time and calcs is why it cost thousands and thousands of dollars. Let�s take one common sense note, if it�s BS then why does the code require it in certain instances?

Once again the study will take into effect the amount of available current and if done correctly will match the equipment to this. You say that a lab can't duplicate the field conditions???. Some labs test some of their gear at 200% in some instances. Take a look at MGE gear and see what they do upon testing/commissioning. So if you are in the field and a splice fails or a phase to phase short and the breaker blows off the wall or does something off normal then you better start looking at who designed it or setup the settings, because in MOST (not all) cases it wasn't correctly installed to handle the fault.

Please before you go any further please read the link I added. It is an example of a study and it is from cooper/bussman. Look at page 1 number two on "SHORT CIRCUIT STUDY"

I do hope you understand this better and that this helps clear things up for you.

""""""Ever seen conductors move under fault current?

You should see power lines jumps. """""

I have a lot of experience in high voltage and yes the air can become a conductor. Where are you going with this?

Here is a link that might be useful: READ THIS LINK! Example of a study and what it includes

Wow, what a crack-up this argument is! It's almost like an argument between repubs and dems, or atheists and christians ... and here all I was looking for was to find out what to recommend to my friend whose electrical panel (or possibly meter) has a buzzing sound audible through much of the house. Didn't know that electricians could have such intense debates ... or that there were electricians who think like conspiracy theorists, that the ratings and tests and such are irrelevant and things will blow up randomly no matter what you do.

Out of curiosity, the "selective coordination" idea--basically you're setting up the fault / breaker sequence to try to insure that an issue in one area of, say, a hospital, trips ONLY ONLY ONLY that specific circuit, so as to prevent a loss of power to a large area of the building, making sure there's no interference with critical systems such as life-support or operating-room lights ... do I have the general idea?

The problem here is that more than half the people here are not electricians.
However most of the posters who aren't understand it's pointless to respond to a thread that has been dead for three months.

This is all good stuff but are you having it inspected?

I just installed a new Main panel on a job and back fed the original panel with 100 amps (originally a 200 amp Murray main panel). Properly isolated the neutral buss bar with the ECLX210M kit.

The inspection department turned it down because it wasn't listed as a sub panel. They required the sticker tag to list the panel as a sub panel. You know darn well that the sticker on every main panel describes the main panel as a main panel. Yet I have this approved for years.
At this point it appears that the only way to go is to gut the panel and make it a junction box. But will they approve that it is not listed as a junction?

Here is a link that might be useful: Frustrated Electrical Contractor

"The inspection department turned it down because it wasn't listed as a sub panel. "

Someone is just incompetent at the AHJ.

Sub-panels are a sub-set of main panels, and do not require a separate listing.

There's no such thing as a "subpanel" listing.

It's either a main breaker panel (which means nothing about how it's used) or a main lugs only. You won't even find the term "main panel" or anything like it in the NEC. You've got a SERVICE DISCONNECT (which may or may not be part of a panel) and everything else.

If the panelboard was marked "Suitable Only for Use as Service Equipment", it cannot be used as feeder panel. The reason is, the neutral is factory bonded to the enclosure. Other panels, such as feeder panels will be marked "Suitable for Use as Service Equipment". (Note the difference, 230.66). BTW in a garage for a SFD you can just use a 3-way or 4-way snap switch as the disconnect. (226.36 Exception)