sub panel questions

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gserve

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Hi, In a residential detached garage a 6 space sub panel is installed by homeowner which can hold 12 circuits(via tandem beakers).#1 does this panel need a main breaker? #2 What is the min feeder capacity? They have 40A feed(#8 conductors)Because there is room for more than 2 circuits (article #225)I say it need a 60 A feeder min. Whats your opinion on this? Code references please. Thank You.
 
Re: sub panel questions

How many breakers are actually installed?
It has a single breaker supplying it so the requirement for a panel to be supplied by one or two OCPDs is met!
What is your calculation that justifies your position on the size of the feeder?
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Tom
 
Re: sub panel questions

I agree that 225.39(D)requires 60amp min. If you have 6 or less breaker throws, no main breker is needed. Only when a 7th. or more is added would you need the main breaker. 225.33(A)
 
Re: sub panel questions

lukewarmwater, I disagree with your position that a main is not required unless there are more than 6 breakers. 225.31 Disconnecting means."Means shall be provided for disconnecting all ungrounded conductors that supply or pass through the building or structure." And 225.32 Location. "The disconnecting means shall be installed either inside or outside of the building or structure served or where the conductors pass through the building or structure." Factor in 225.38(B)"Each building or structure disconnecting means shall simultaneously disconnect all ungrounded supply conductors that it controls from the building or structure wiring system." If you have more than one breaker you would need a main to simultaneously disconnect all ungrounded supply conductors. The only situation where a sub panel would not need a main is when the sub panel is in the same structure as the main distribution panel or the sub panel contains only one over-current device. When there is only one circuit supplied to a separate structure on resiential property the exception in 225.38 allows the disconnect to be a snap switch or set of 3-way or 4-way switches.
 
Re: sub panel questions

There are 3 breakers installed, 1 for outlets, 1 for lighting and 1 240v 20a outlet for air compreeser. What size feeder would you install?
 
Re: sub panel questions

Don, Does 225.38(B) apply to each of up to 6 breakers in a subpanel in a separate structure? I was always under the assumption that 225.30 limited the number of feeders or branch circuits to additional buildings or structures to 1 per unless one of 225.30 A-E was met. So if you had 1 feeder serving a separate building or structure you would need to disconnect all ungrounded conductors serving that building simultaneously at that building. I thought 225.33 applied to where the feeders originated from the MDP. I could be wrong and probably am. Please clarify.
 
Re: sub panel questions

amptech,
Yes, 225.38(B) applies to each of six breakers that are permitted by 225.33.
Each building or structure disconnecting means shall simultaneously disconnect all ungrounded supply conductors that it controls from the building or structure wiring system.
Click to expand...
The key words are "each disconnecting means" and "that it controls".
Don
 
Re: sub panel questions

i believe that a main is needed because 12 "breakers" -- twins could be used, and by poster's question this leads me to believe that this may happen.

60A min.
 
Re: sub panel questions

I do not believe what "could happen" has anything to do with this.

If this was 6 fused disconnect switches nothing would stop someone from adding a seventh other then the fact they should know the code.
 
Re: sub panel questions

So, Is the consensus that there be a main breaker added to this panel and that it be 60A min? Also the feeder be sized for 60A min?
 
Re: sub panel questions

I will probably get shot down here. If you carry this logic through you would have electrical inspectors passing main lug 40 space panels (no main) for dwelling services as long as there are no more than six breakers installed at the time of the inspection. Before you say it, I agree no electrician would do that. I am only trying to make a point. You are saying if a homeowner installs this I should pass it. You are saying it is code compliant.

I ask again is the panel listed as a service disconnect with out a main?

408.16 Over current Protection.
(A) Lighting and Appliance Branch-Circuit Panel board Individually Protected. Each lighting and appliance branch-circuit panel board shall be individually protected on the supply side by not more than two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panel board.

And I know this always gets thrown into the discussion, but this panel would also be classified a Lighting and Appliance panel board, limiting the main to max. two disconnects.
 
Re: sub panel questions

Thanks Don. I stand corrected. My apologies to luke warmwater. I agree with iwire. You can't wire for what someone may add in the future. You could install a MLO 20 space panel in an unattached building fed with #6 feeders with 6 two pole breakers in the MLO 20 each feeding a 12 space MLO panel of their own in that same building and still be code compliant. Even with the potential of having 80 single pole breakers and 6 two pole breakers fed with a set of #6 feeders from another structure. You would have to be a moron to do this but I'm sure we all know someone who would. You can try to make a job idiot resistant but you simply can't make it idiot proof.
 
Re: sub panel questions

Dan,
As I understood what Don pointed with regard to a similar question on another forum correctly, that if one were to fill a 6/12 panel with six full size breakers, thus filling the six space panel, then you would comply with the maximum of 6 disconnects as far as the initial inspection is concerned.
It is of my opinion that it would be up to the AHJ to make the judgment whether to accept the original installation under the six circuit disconnect rule or to reject it under the assumption that it could be violated in the future.
 
Re: sub panel questions

amptech, no apology needed. You can disagree with me whenever you want, I'm not always right, not always wrong. Besides, I like to argue. It exercises my mind.
I will say that I would install a main breaker if at all possible.
 
Re: sub panel questions

David, Exception #1 covers your argument. As long as the feeder OCD does not exceed the rating of the panelboard, the 408.16(A) requirement is not applicable. Which brings me to the question of, is there a way to compliantly have a feeder OCD larger than the rating of the panel board? 408.13 says the panelboard cannot have a rating less than min. feeder capacity, or is this a next size higher OCD situation.
 
Re: sub panel questions

Originally posted by david:
I will probably get shot down here. If you carry this logic through you would have electrical inspectors passing main lug 40 space panels (no main) for dwelling services as long as there are no more than six breakers installed at the time of the inspection. Before you say it, I agree no electrician would do that. I am only trying to make a point. You are saying if a homeowner installs this I should pass it. You are saying it is code compliant.

I ask again is the panel listed as a service disconnect with out a main?

408.16 Over current Protection.
(A) Lighting and Appliance Branch-Circuit Panel board Individually Protected. Each lighting and appliance branch-circuit panel board shall be individually protected on the supply side by not more than two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panel board.

And I know this always gets thrown into the discussion, but this panel would also be classified a Lighting and Appliance panel board, limiting the main to max. two disconnects.
Click to expand...
David
Your question about the listing is very apropos but I haven't purchased one of those smaller panels in years that was not listed as service equipment when certain conditions are met. The conditions I have encountered are that not more than six breakers are installed or that a back fed main be installed with an anchor kit. In this case the first condition is met. The fact that you might install more breakers later is a non issue. As IWIRE has already pointed out any trough and disconnect service can have additional disconnects installed after the inspector departs. Some idiot could also remove the main breaker and replace it with lugs in any convertible panel assembly. You can only inspect what is there at the time of inspection. If you turn down the installation based on the likelihood of a future violation you are ignoring a basic principal of law. No agent of the government can take action against a future bad act. The phrase is somewhat over used but that truly is black letter law.

The feeder breaker meets the requirement for not more than two disconnecting means for a lighting and appliance panelboard. The language of exception one clearly exempts panels when "the panelboard feeder has overcurrent protection not greater than the rating of the panelboard."

I have used the six breaker rule to update homes that have multiple sub panels when the owners are elderly or disabled on fixed incomes. The solution is not elegant but installing a twelve slot MLO panel that is listed for use as service equipment when not more that six main disconnecting means are installed and then running individual feeders and branch circuits to existing panelboards or larger loads can cut the cost of a heavy up in half. You only have to make sure that you convert the original service equipment panel to a four wire feeder supplied panelboard by installing the appropriate Buss bar and terminating the neutrals and grounds onto the correct bar. I've had two inspectors who really hated it but both eventually agreed that it was code compliant. The SquareD panel I use for this is available with a QOM2 main breaker but I do not want a single main breaker when the equipment supplies the current to a water pump that will also be used for first aid firefighting.
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Tom

408.16 Overcurrent Protection.
(A) Lighting and Appliance Branch-Circuit Panelboard Individually Protected. Each lighting and appliance branch-circuit panelboard shall be individually protected on the supply side by not more than two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard.
Exception No. 1: Individual protection for a lighting and appliance panelboard shall not be required if the panelboard feeder has overcurrent protection not greater than the rating of the panelboard.

[ March 10, 2003, 11:59 AM: Message edited by: hornetd ]
 
Re: sub panel questions

Originally posted by templdl:
Dan,
As I understood what Don pointed with regard to a similar question on another forum correctly, that if one were to fill a 6/12 panel with six full size breakers, thus filling the six space panel, then you would comply with the maximum of 6 disconnects as far as the initial inspection is concerned.
It is of my opinion that it would be up to the AHJ to make the judgment whether to accept the original installation under the six circuit disconnect rule or to reject it under the assumption that it could be violated in the future.
Click to expand...
templdl
If you were looking for a sore spot you found it. Rant mode is on! :mad: I am passionately opposed to any tolerance for inspectors making up amendments to the code as they encounter situations that do not fit their personal views of what the best practice would be. This is exactly the same thing as a police officer trying to ticket you for driving to endanger because you were driving at a slower speed than he/she thought was safe when you are going at a speed that is between the minimum and maximum speeds allowed by law.

Acting on "the assumption that it could be violated in the future" is an inherent abuse of power. I will repeat what I said earlier. Presuming a future bad act is something no public official may lawfully do. An inspectors power is limited by law to enforcing the code as written. It is a basic axiom of the law that all that is not forbidden is permitted. An appointment as an electrical inspector does not make you a super majority that can over rule the legislature and executive of your state or local government. When an inspector enforces personal preference as law he/she is abusing the power of the office by arbitrarily and capriciously wielding the police powers of the state. The mere fact that the absence of accessible appeals processes in many jurisdictions allows those few inspectors who are inadequately trained and supervised to behave as little tin pot gods year after year does not make their conduct right. In the end the entire society pays the increased cost of electrical construction caused by the complete unpredictability of inspection compliance in some jurisdictions. The Henry M. Robert quote "Where there is no law, but every man does what is right in his own eyes, there is the least of real liberty." applies to those enforcing the law as it does to those constrained to obey it.
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Tom
 
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