Max amperage off a sub panel?

[Rich Sumen]

Does anyone know what the maximum amperage would be allowed from a 100 amp sub panel to power another sub panle?

I observed a 200 amp main in a home, powering a 100 amp sub. This 100 amp sub had 4 - 20 amp breakers to various rooms, and it also powered (with a 100 amp breaker) an additional 100amp panel in the garage. I think I remember reading that you can only pull 70 ot 80% of a panels capacity, out to another panel.
Anyone know what's proper or code?

Thanks

[Jerry Peck]

Well ... ;) ... first you would need to bring the sub up onto dry dock so we could look at it.

You mean what is the most you can feed off one PANEL to another PANEL when the first PANEL is 100 amp?

100 AMP.

More than that and breakers will be tripping upstream somewhere. :)

It all depends on the PANEL, the panel may have breaker tabs rated only for 70 amp breakers. Then you would need to do some load calculations to figure out what was going to be on with what so as to not trip the 100 amp main protecting the first 100 amp panel.

[Garry Sorrells]

Jerry,
Doesn't it just boil down to a load calculation for the circuits and breakers?
If the house main was 200 amp in an appropriate panel and you had 40 - 100amp panels that fed off of that main each one having a main for that panel which feed other breakers in that panel, it still would be all about load calculations and the correct breaker for the size wire used??

[Jerry Peck]

Gary,

He had a 200 amp panel (presumably with other loads on that panel) feeding a 100 amp panel (with other loads on that panel) feeding a 100 amp panel.

*IF* the most-downstream 100 amp panel is to be used to it maximum, then nothing could be used in the intermediate 100 amp panel as the breaker protecting that intermediate 100 amp panel would trip.

Yes, it is all about what loads are where, but at some point there is a point of diminishing returns on what one thinks they are getting.

Think of it this way, if you feed a 3/4" garden hose from the hose bibb, which feeds a two-way tap to two 5/8" garden hoses a) and b), and one of those garden hoses, a), feeds two 1/2" garden hoses, and ... you turn the 5/8" garden hose b) on full blast, you will not get much out of the two 1/2" garden hoses, and you will not be able to use the 3/4" garden hose for much of anything at all without after 5/8" garden hose b) output.

Will the above set up work if all things are only partially opened? Sure. But someone seeing that 100 amp panel in the detached garage may think 'Hey, I can plug my welder in there, and my table saw, and my ... and THINK they have sufficient power ... until someone in the house turns the a/c and the water heater on ...

Yes, it is all about loads, but the designer (if there was one) should have thought about the loads and limited the farthest panel to a 60 amp panel or something like that. Just for common sense - the code does not address things like that.

[dana1028]

Well ... ;) ... first you would need to bring the sub up onto dry dock so we could look at it.

You mean what is the most you can feed off one PANEL to another PANEL when the first PANEL is 100 amp?

Jerry aren't you getting tired of this crusade of yours yet?

This is a universally accepted term [sub-panel], like it or not, by most folks in the electrical trade - it is used by tradesmen, electricians, inspectors, instructors, etc.

If you do a web search you will find 1000's of references for this.

Just because you don't like this term doesn't mean it is not a legitimate term.

Example: For years I hated people using the term forte improperly [i.e. they were using this musical term instead of the correct word, fort, as their strong point]. Finally, so many people were using this term incorrectly that the dictionaries now include this definition [strong point] under the word forte. Can't help myself, I still cringe when people use this term - but I KEEP MY MOUTH SHUT.

In other words - get over it already - the world is against you and you are sounding like an old biddy.

[H.G. Watson, Sr.]

Does anyone know what the maximum amperage would be allowed from a 100 amp sub panel to power another sub panle?

I observed a 200 amp main in a home, powering a 100 amp sub. This 100 amp sub had 4 - 20 amp breakers to various rooms, and it also powered (with a 100 amp breaker) an additional 100amp panel in the garage. I think I remember reading that you can only pull 70 ot 80% of a panels capacity, out to another panel.
Anyone know what's proper or code?

Thanks

Nope. Temperature rating of equipment and panel ratings, listed, labeled limitations, bus stab ratings, etc. of the various panelboards being described.

No idea type or style of panels, could very well have sub feed through. No assumptions series connected short circuit ratings, if are - can have a 200A breaker/disconnect supplying a 60 amp sub feeder for example, the "protection" is on the "other" end (termination).

Without the correct information and details (example apparently two panels ahead of "garage" attached or detached, separate structure, who knows, etc.). 70 or 80 percent of ??? has nothing to do with it. Calling something a "100 A panel" is meaningless by itself and communicates little without requiring a LOT of assumptions as to your intended description(s).

There is "more than one way to skin a cat". Temperature limitations, weakest link in the chain. More, or higher not always better nor always permitted. With disjointed vague post, there is no singluar answer, except to say unclear, incomplete information and question(s) to respond further.

[Jerry Peck]

Jerry aren't you getting tired of this crusade of yours yet?

This is a universally accepted term [sub-panel], like it or not, by most folks in the electrical trade - it is used by tradesmen, electricians, inspectors, instructors, etc.

Nope. Not when the mis-application of that term leads to the confusion that it leads too.

Being willing to encourage the use of that term with the obvious presence of the confusion leads one to wonder about the willingness of such a person to try to do things correctly and make sure that others can understand when and where to do something and when and where not to.

[Rich Sumen]

Wow,
I didn't mean to start anything.
Just looking to see if there was any "Electrical code or guideline"
on powering one panel (A Remote Distribution Panel) from a another
panel.
Anyone Know or any "codes" apply?

Rich

[Bill Kriegh]

Rich, the short answer is to read the labels in all the involved panels. This tells you the max breaker size that can be installed on the buss of the first panel in line, the max rating of the buss in the second panel, the max breaker size on the second panel's buss, and on and on down the line.

The long answer is a bit more complicated. It involves calculating all the loads involved and making sure all the panels in line can handle the loads and any fault currents.

I hope you don't get put off by all the mumbo jumbo but dealing with the NEC and the attendant hookups is seldom as simple as read "A" and it tells you all you need to know. And, many times "B", "C", and "D" may not tell it all to you either. Best advice is if you aren't familiar with what you find get a hold of someone who is. The book says it's not supposed to be an instruction manual. You'd be well advised to take that to heart when trying to figure out if something is OK or not

And, excuse Watson. He just can't help himself.

[Rich Sumen]

Thanks Bill. I appreciate it. Here is some more info.

Panel "A", 100 amp sub. (Rated for 100 amp, proper feed wire, 10 feet from the main with a 100 amp breaker in the main. It also has a 100 shut off into the panel) The main powering it is 200 amp, all proper.

Panel "B", another 100 amp sub panel (Rated for 100 amp, proper feed wire, located 100 feet from sub panel "A", powered from a 100 amp breaker that is in sub A)

I guess this is OK, from what I'm reading and I know that if say, 70 amp is being used from "A", that "B" will not be able to pull the full 100 amp as, the upstream panel (A) is limited to its overcurrent protection of 100 amps.
Pretty much, common sense.
I was just trying to find out if this was a violation of a code or should be reported as "improper"?

It appears I should be posting this on an another "Electrical Forum" perhaps.

[H.G. Watson, Sr.]

You still haven't clearly identified the service equipment, or first panel "wiring diagram", etc. Although it is obvious others have assumped a singluar MCB; and a series rating method, as opposed to a full rating application.

There is more than one way to skin a cat. Note you made a special point of mentioning the next panel was 10 ft.

I've posted these self-study modules before, suggested reading:

http://www.colorado.edu/ceae/classes/aren4570/panelboardspaper.pdf

http://www.enm.com/eandm/training/siemenscourses/panelboards.pdf

This can be/is effected by the local POCO rules regarding service equipment, the NEC, local ammendments to same, the NEMA and UL Standards applicable to the equipment of vintage of manufacture, the Listed instructions, labeling, and limitations of the equipment, and how employed amongst others, and considerations required as later modifications/additions/replacements made to the overall system.

See standards of vintage of equipment manufacture, UL marking guides, listed instructions, labeling, etc. of equipment, etc.

I think you may have some confusion over just "how" molded case circuit breakers actually perform in various "situations", and the different types of circuit breakers "behave" differently/time/sensitivity/in different "situations" depending on their type, rating, etc.

I also think you may have some confusion over the different types of "loads" or "pulls" as you call it. Not all "loads" are purely resistive. Simplified electrical theory is often taught or discussed in the form of a simple DC circuit - hence the idea of electricity "flowing" or "pulling" in one direction. AC does not get "pulled" or "flow" in a one-way direction, in the manner of a simplified DC battery circuit.

Controlled short circuit vs. work, etc. Presume your "pull" reference regarding "work" and/or "duty". Momentary peaks, inrush, slow climb, vs. time; and the type of "load", etc. and if, for example the "continuous duty" rating is full or 100% or more common in residential - 80% rating. If the equipment and MCCBs are temperature rated as 60C, 75C or 60/75C and their application to other equipment is matched, etc. etc. (example a factor when discussing those of the size you indicate in your vague example (100A) etc.)

present UL marking guide for Molded Case Circuit Breakers may begin to assist you in understanding SOME of the distinctions with differences in applications: http://www.ul.com/global/documents/offerings/perspectives/regulators/electrical/newsletters/MoldedCaseCircuitBreakersMG.pdf

Would be further helpful to understand if that first equipment is a power panelboard (2005 NEC or prior) combo equipment, etc. and configuration was clear.

Hope you're "picking up" what I'm putting down.

Short answer - it depends, and you're not having provided enough to reasonably and correctly answer in the most minimal fashion without having to make a huge series of assumptions which may not be correct to your proposed situation. Appears it is not a hypothetical but an actual installation, so please provide the details, photos, wiring diagram with specifics.

If this is a proposed DIY question not an inspection/education question, please so clarify, because the return to asking "is there any code..." etc. is off-putting.

Perhaps you've got this distant panel 110 feet plus away in a separate structure with a mixed use or inductive loads, not purely resistive, subject to and protecting for voltage drop.

Still unclear just what your question really IS, or what exactly IS the path from POCO to distribution panel or disconnect and what equipment is involved.

[H.G. Watson, Sr.]

Wow,
I didn't mean to start anything.
Just looking to see if there was any "Electrical code or guideline"
on powering one panel (A Remote Distribution Panel) from a another
panel.
Anyone Know or any "codes" apply?

Rich

ahh...yeah.:rolleyes:

Depends on what and where the installation is and the application!! e.g. POCO distribution, TelCO, premisis, watercraft, vehicle, federal, state, local, etc. Missle silo, fire suppression or alarm system, communications, CD, home, business, MAX VOLTAGE of system, refrigeration equipment, welding equipment, etc. etc. presence of switches, fuses, MCCBs, Source and type of power system, etc. etc.

[H.G. Watson, Sr.]

Jerry,
Doesn't it just boil down to a load calculation for the circuits and breakers?
If the house main was 200 amp in an appropriate panel and you had 40 - 100amp panels that fed off of that main each one having a main for that panel which feed other breakers in that panel, it still would be all about load calculations and the correct breaker for the size wire used??

Nope.

For example, voltage drop, ambient temperatures, equipment temperature ratings, short circuit ratings, duty ratings, and much, much more.

[Rich Sumen]

"G.R. Watson Sr." need not reply any more! Please!
He is absolutely, no help at all!

Thank You, to all the others.

[Bill Kriegh]

Rich, the easiest way for you to deal with Watson is put him on the "ignore" list. Threads flow amazingly well and the distractions are gone. If you elect not to do that, just be aware that all the threads he gets involved in rapidly turn into a game of oneupmanship and folks with things to contribute get driven away. Shame. Excellent forum otherwise.

[Rich Sumen]

Thanks Bill, I took your advise.
I was starting to think I came across an "Inspector's Metal Rehab" forum for a moment there!

Regards

[Jerry Peck]

Rich,

The sad part about H. G. is that he IS a very knowledgeable person, the problem is that his beside manner is akin to a doctor who tells his patient that the patient has a terminal disease and will die soon, then walks out as if nothing bad was said, only to walk back in 10 minutes later and say "Why are you still here? I told you you were going to die, so get it over with already."

[Paul Johnston]

sub-
prefix
1 at, to, or from a lower level or position : subalpine | sub-basement.
• lower in rank : subaltern | subdeacon.
• of a smaller size; of a subordinate nature : subculture.
• of lesser quality; inferior : subhuman | substandard.
2 somewhat; nearly; more or less : subantarctic.
3 denoting a later or secondary action of the same kind : sublet | subdivision | subsequent.
4 denoting support : subvention.



Nope. Not when the mis-application of that term leads to the confusion that it leads too.

Being willing to encourage the use of that term with the obvious presence of the confusion leads one to wonder about the willingness of such a person to try to do things correctly and make sure that others can understand when and where to do something and when and where not to.

[Guy W Opie]

Basicly any size panel can be fed by another panel, providing that the TOTAL calculated load does not exceed the amperage rating of the incoming service.
If one is not sure about doing load calcs than I would suggest getting licensed electrician to come in an do the calcs for you.

[Chris Roth]

Does anyone know what the maximum amperage would be allowed from a 100 amp sub panel to power another sub panle?

I observed a 200 amp main in a home, powering a 100 amp sub. This 100 amp sub had 4 - 20 amp breakers to various rooms, and it also powered (with a 100 amp breaker) an additional 100amp panel in the garage. I think I remember reading that you can only pull 70 ot 80% of a panels capacity, out to another panel.
Anyone know what's proper or code?

Thanks


Rich;

I had a basement finished back in 2002 and had to bring a SUB-PANEL into the basement. The basement was only 458 sq. ft. Anyway the Main Panel Box was rated @ 100 Amps for the house. To bring a 60 Amp service into the basement to run A/C and electrical outlets I had to do some swapping or double-up on some of the lights in the main panel. After that was accomplished the regional inspecter signed off on my permit. Oh I forgot to mention, since I had only a 100 AMP MAIN the main electrical feed was copper so legally I removed the 100 AMP MAIN BREAKER and replaced it with a 125 AMP BREAKER in which was also signed off. You can't do that if your main electrical feed is aluminum.

Chris

[Joseph Peake]

Jerry,
Just so you know, your clarification of terms is well received in some circles.
Some time ago, I changed the wording in my reports from "sub panel" to "distribution panel".

Here's another one, "footing vs footer".

"Never give in, never, never, never".

[Donald Farrell]

Rich,

It's a two step process.

1) The max size breaker that the Main Service panel can take is set by the manufacturer of the panel. Once that is determined:

2) The "Load Calc." needs to be presented to verify that there is adequate amperage to service the load.

Most home owners just plug in the new panel without taking that step. Some electricians will by-pass the Load Calc. and just do what they were hired to do.

Don

[Paul Johnston]

I think Jerry will tell you it is a remote panel.



Jerry,
Just so you know, your clarification of terms is well received in some circles.
Some time ago, I changed the wording in my reports from "sub panel" to "distribution panel".

Here's another one, "footing vs footer".

"Never give in, never, never, never".

[Joseph Peake]

uh oh....

[Phil Brody]

So H.G. is analogous to "House" entertaining and knowledgeable, still good info elect to learn what you will.

[Rick Cantrell]

still good info elect to learn what you will.

More like
if you can follow

[Donald Farrell]

Paul,

I choose to take umbrage with your comment for two reasons.

1) I never used the term, "Sub-panel" in my response. I did use the term "Main service panel"

2) I agree with Jerry's position. However, if you can point me to the definition of "Sub-panel" in the NEC, I'll be happy to apologize to you.

Don

[Donald Farrell]

Rich;

I had a basement finished back in 2002 and had to bring a SUB-PANEL into the basement. The basement was only 458 sq. ft. Anyway the Main Panel Box was rated @ 100 Amps for the house. To bring a 60 Amp service into the basement to run A/C and electrical outlets I had to do some swapping or double-up on some of the lights in the main panel. After that was accomplished the regional inspecter signed off on my permit. Oh I forgot to mention, since I had only a 100 AMP MAIN the main electrical feed was copper so legally I removed the 100 AMP MAIN BREAKER and replaced it with a 125 AMP BREAKER in which was also signed off. You can't do that if your main electrical feed is aluminum.

Chris

Chris,

Are you an electrician or an electrical inspector? So, you "legally" changed the main breaker for 100A to 125A because you ran copper conductors as your Service Entrance Conductors?

Have you ever read NEC Table 310.15(B)(6)? If you have not than I'm sure that you do not realize that you have a code violation staring you in your face. Unless your service point is already wired for a amperage greater than 125 amp, than you have the wrong size conductors in use and it is a fire hazard.

100A service requires a min. copper conductor of <TYPO -I meant 4 AWG, not 1AWG>. 125A service requires a min. copper conductor of 2 AWG. Now, if as in our area, Dominion Power has pre-wired the area with 4/0 AL SER cable. So that they could up-grade service to customers as high as 200A without having to change out the conductors for the upgrades. And the meter base has 4/0 AL conductors, you would be fine.

Regardless, putting a larger breaker in without increasing the service size from the utility is an exercise in futility.

However, just changing the breaker to 125A from 100A is meaningless unless you had the service increased by the utility.

[Chris Roth]

Chris,

Are you an electrician or an electrical inspector? So, you "legally" changed the main breaker for 100A to 125A because you ran copper conductors as your Service Entrance Conductors?

Have you ever read NEC Table 310.15(B)(6)? If you have not than I'm sure that you do not realize that you have a code violation staring you in your face. Unless your service point is already wired for a amperage greater than 125 amp, than you have the wrong size conductors in use and it is a fire hazard.

100A service requires a min. copper conductor of 1 AWG. 125A service requires a min. copper conductor of 2 AWG. Now, if as in our area, Dominion Power has pre-wired the area with 4/0 AL SER cable. So that they could up-grade service to customers as high as 200A without having to change out the conductors for the upgrades. And the meter base has 4/0 AL conductors, you would be fine.

Regardless, putting a larger breaker in without increasing the service size from the utility is an exercise in futility.

However, just changing the breaker to 125A from 100A is meaningless unless you had the service increased by the utility.


No I am not a electriction by any means. When the regional Building Inspecters reside I had to pull an electrical permit to install a sub-panel in the basement. No I did not run a new feed into the MAIN PANEL as you suggest. The inspector allowed me to change the 100 AMP Service Breaker to 125 AMP SERVICE BREAKER "LEGALLY". The main feed WOULD ALLOW THAT ACCORDING TO THE REGIONAL BUILDING INSPECTERS. So do me a favor and quit making a mountin out of a an ant hill.

[Donald Farrell]

Chris,

I am not trying to be a horse's fanny. What you did is not as simple as you think.

You are absolutely correct. Why should I care that you may have a melt down because you have the incorrect conductor size for your service entrance conductors.

The ampacity of a conductor is strictly defined within the NEC. It is dependent on the type of insulation, the type of conductor, the type of connection being used, the temperatiure of the conductors and connection in use.

Also, a "Building Inspector" does not necessary mean an "Electrical Inspector". It means a "Building Inspector" and while it is true that "Building Codes" include "Electrical Codes" it does not mean a Building Inspector knows the NEC. Two different animals. It may be true in your instance but it also may not.

For example, if your home was built to a 100A service, it is unlikely that the electrician put in copper conductors for 200A to your Main Service Panel. The dollar cost of copper over aluminum is significant.

Also, is the panelboard you have installed capable of taking larger conductors.

Conductors that are to small for the load will overheat, insulation will melt. Fire can and does happen.

If you pulled a permit for the service change than fine. If an inspector signed off on conductors without seeing them then shame on him/her. But in either case, you are the one that might have a fire on their hands. Not me and not the inspector.

[Chris Roth]

Chris,

I am not trying to be a horse's fanny. What you did is not as simple as you think.

You are absolutely correct. Why should I care that you may have a melt down because you have the incorrect conductor size for your service entrance conductors.

The ampacity of a conductor is strictly defined within the NEC. It is dependent on the type of insulation, the type of conductor, the type of connection being used, the temperatiure of the conductors and connection in use.

Also, a "Building Inspector" does not necessary mean an "Electrical Inspector". It means a "Building Inspector" and while it is true that "Building Codes" include "Electrical Codes" it does not mean a Building Inspector knows the NEC. Two different animals. It may be true in your instance but it also may not.

For example, if your home was built to a 100A service, it is unlikely that the electrician put in copper conductors for 200A to your Main Service Panel. The dollar cost of copper over aluminum is significant.

Also, is the panelboard you have installed capable of taking larger conductors.

Conductors that are to small for the load will overheat, insulation will melt. Fire can and does happen.

If you pulled a permit for the service change than fine. If an inspector signed off on conductors without seeing them then shame on him/her. But in either case, you are the one that might have a fire on their hands. Not me and not the inspector.


Don;

Thanks for the info. The inspecter is a certified electriction. Anyway does not matter. He did inspect the main feed and it WAS copper and not aluminum. So I pulled a 60 AMP sub panel into thew basement and out of that 30 AMP to the A/C.

[Rich Sumen]

Wow, there sure are a lot of "know it alls" here, and lot of egos also.
What about discussing conditions from a "inspectors" point of view,
on this "inspectors" forum, talking specific codes and or verbage.
Is this an "Inspection forum"? Or just a place for people to argue with each
others. Talk Codes, or what an "Inspector" would discuss or write.

[Guy W Opie]

If the main serice is for a dwelling the correct wire is this.
#4 cu or #2 al ,per 310-15(b)(6), if it's a 'dwelling'

[Rollie Meyers]

If the main serice is for a dwelling the correct wire is this.
#4 cu or #2 al ,per 310-15(b)(6), if it's a 'dwelling'

Correct. IF the panel carries the entire load of the dwelling, it cannot be used for a subfeed to another panel or outbuilding.

[Jerry Peck]

I think Jerry will tell you it is a remote panel.

I would not, do not, refer to them as remote panels as that indicates the panel is remote from something else, and "remote" is usually taken as meaning "far away".

There is "service equipment" and 'not service equipment', and using the term "remote panel" just seems strange when you are referring to the panel which is setting right next to the service equipment.

Thus, why do some people insist on adding un-needed wording to a a panel when it can be called a "panel".

Joseph, glad to hear that some get it and can understand why things are presented as they are, thank you. :cool:

[Jerry Peck]

So H.G. is analogous to "House" entertaining and knowledgeable, still good info elect to learn what you will.

"House" is entertaining, H. G. is not, "borish" would be a better description of H. G.

Of course, though, H. G. would say something like 'You probably mean "boorish".'

Which reminds me of a joke I heard on NPR today on a show about the English language:
- A Georgia boy enrolls into Harvard and meets an upperclassman there, the Georgia boy asks the upperclassman "Do you know where the library is at?"
- The Harvard upperclassman, in true Harvard fashion and to show his superiority replies "This is Harvard, at Harvard you do not end a sentence in a preposition."
- The Georgia boy looks at the upperclassman and replies "Okay, I will state my question without ending it in a preposition: Do you know where the library is at, jerk?" :D

[Donald Farrell]

Rich,

I'm very new here. My comments were not made out of ego or to "show off how much I might or might not know". They were about safety, for both the facility and the family inside of it. Safety is something we all live and die by in the electrical field.

Using undersized service conductors and swapping out a MCB for a larger size are just flat out unsafe. Thinking that because I have a copper conductor I can just increase the amperage without any concerns is foolish. Let's extrapolate that one. Lets see, I have a 20A circuit and I want to put a 120 water pump that draws 30 amp. By this poster's statement, that's fine because the existing circuit is made with copper conductors. Thinking that because I change out the MCB I increased my electrical service is foolish.

Then again, the inspector that did approve the installation was a certified electrician. By the way, what exactly is a certified electrician. I know of apprentice, journeyman and master, but not certified.

If I stepped on toes, I apologize. My purpose was to warn the poster that he may have a serious problem.
:confused:

[Rich Sumen]

Member
Join Date: Feb 2011
Location: Ohio
Posts: 7


Re: Max amperage off a sub panel?


Don,
I think your answering a different "Rich".
I dont know how a simple question got into all this conversation. I had a simple question.......
Are there are codes, or guidlines on how much amperage could be pulled off a panel (Say a 100 amp,) to power a distribution panel. You see sub panels very offten, 30, 50, 70, 100amp... of a )lets say, a 100 amp main). But is there a limit?
This is a very "odd forum". And just going by my first post, very hard to get any commen sense answers.
No offense to anyone.
-------------------------------------------------------------------

[Jerry Peck]

I dont know how a simple question got into all this conversation. I had a simple question.......

Rich,

One thing you will find out about this site is that, yes, you will get your simple answer (you actually did get it, you either missed it or did not recognize it) AND you will get much additional information for things you may not have considered but which others feel is worthy for others (not just the person asking the original question) - that thread drift does, much of the time, lead to a lot of the learning which goes on here.

Ask a simple "Is the grass green?" and you will get information about chlorophyll and the care of grass and plants in general, and, yes, the question of "Is the grass green?" gets answered the vast majority of the time.


Are there are codes, or guidlines on how much amperage could be pulled off a panel (Say a 100 amp,) to power a distribution panel. You see sub panels very offten, 30, 50, 70, 100amp... of a )lets say, a 100 amp main). But is there a limit?

You were given that answer here, in post number 6:

Temperature rating of equipment and panel ratings, listed, labeled limitations, bus stab ratings, etc. of the various panelboards being described.

You just had to dig for it:
Q. "Are there are codes, or guidlines on how much amperage could be pulled off a panel (Say a 100 amp,) to power a distribution panel."
A. " ... panel ratings, listed, labeled limitations, bus stab ratings ... "

The other answer regarding what code reference would be: 110.3(B), which relates to the A. above in listing and labeling, in which you would find the bus stab ratings.


This is a very "odd forum".

Yes, this is where the learning really happens as everyone shares their knowledge with others, whether the others like it or not.

Join the fray, share what you know with the rest of us when we ask questions on things we do not know. :cool:

[H.G. Watson, Sr.]

Funny how he wastes four posts with unprofessional personal insults and then resorts to quoting the answer to the OP's question (and repeated follow-ups), from MY post isn't it? The OP didn't ask for code citations, nor was he specific.

[Jerry Peck]

Funny how he wastes four posts with unprofessional personal insults and then resorts to quoting the answer to the OP's question (and repeated follow-ups), from MY post isn't it? The OP didn't ask for code citations, nor was he specific.


Funny how Watson cannot take an indirect compliment by someone pointing out that Watson actually answered the question.

What is NOT funny is how many posts, and such verbose posts at that, with such effluent too, that Watson spews forth in NOT answering any questions.

[Garry Sorrells]

Thanks Bill. I appreciate it. Here is some more info.

Panel "A", 100 amp sub. (Rated for 100 amp, proper feed wire, 10 feet from the main with a 100 amp breaker in the main. It also has a 100 shut off into the panel) The main powering it is 200 amp, all proper.

Panel "B", another 100 amp sub panel (Rated for 100 amp, proper feed wire, located 100 feet from sub panel "A", powered from a 100 amp breaker that is in sub A)

I guess this is OK, from what I'm reading and I know that if say, 70 amp is being used from "A", that "B" will not be able to pull the full 100 amp as, the upstream panel (A) is limited to its overcurrent protection of 100 amps.
Pretty much, common sense.
I was just trying to find out if this was a violation of a code or should be reported as "improper"?

It appears I should be posting this on an another "Electrical Forum" perhaps.


Rich,
At times this site gets a little wacky and off the original topic.
The people that respond are quite diverse in their backgrounds and personalities.
This diversion makes the input by its responders unique and at times very trying.
You will receive an answer and a whole lot more. Sometimes it just requires separating out what best answers your question.
By going to an site of only electricians you is not bad for conformation but you will not get some of the humor that you can receive here at this site.
Take all things with a grain of salt.

The simplistic answer on the basic information as if it were on a test is that there is no code violation against the number of panels used.
The rest is a mater of how they are used, with all of the details that would be required to determine if they then met code.

You might ask why would a 100amp panel be used instead of a 30amp panel if only one breaker is needed?
If the home owner is offered the option for a larger panel that will offer a wider range of options in the future for a few dollars more and says OK.
The difference in cost is not much for the actual equipment. Today the cost of the wire is now the big cost (copper) in running the lines.
The labor to screw a 30amp or a 100amp panel to a wall is the same, so why not go for future options.
I would think that an electrician might not tell you the basis on why they sell different equipment when it is just about creating a job in the future. (((( $$$$$ for them)))