Feeders

[Atlas Shrugs]

Hello everyone,

Honored to be posting my first post here, and it is regarding a drawing I am looking at. The architects are asking for a 60 amp subpanel to be fed from a 60 amp breaker. The new 60 amp subpanel is to feed a 100 amp subpanel with a 100 amp breaker. I am somewhat confident that you are not allowed to feed a higher ampacity panel from a lesser one. I am having difficulty locating why this is so in the code book.

Thank You all for any help that may come.

 

[don_resqcapt19]

As far as I know, you will not find such a rule in the NEC.

 

[Atlas Shrugs]

But could it not potentially cause the 60 amp breaker to trip?
The NEC does not care if the circuits trip as long as it is protected?
Should the owner be advised to change it to 100 amps and not 60 amps?

 

[GoldDigger]

On the other hand, except for photovoltaic or other interactive generation or the simple size of the panel, it is hard to think of a solid reason for doing it?

Tapatalk!

 

[John120/240]

What he said.^^^ You can't get any more out of your 60 A sub panel than what you put in.

 

[Atlas Shrugs]

As long as the circuit is protected it does not matter that it is feeding off a lesser amperage circuit?
Could there not be a potential for tripping on the 60 amp breaker?
Should the owner be advised to upgrade the breaker and wiring?

 

[Dennis Alwon]

As long as the circuit is protected it does not matter that it is feeding off a lesser amperage circuit?
Could there not be a potential for tripping on the 60 amp breaker?
Should the owner be advised to upgrade the breaker and wiring?

That is correct. If the 60 amps is the capacity of the service I could add a 200 amp main breaker panel as long as the load does not exceed 60 amps.

Think of it like this-- suppose instead of a 200 amp breaker that was a main lug panel. You could always potential have too much ampacity but the 60 amp main breaker would trip if that were the case. The idea is to not over load it.

 

[augie47]

I have run across your scenario before but normally with a UPS or some type standby power.
Sometimes the job calls for more individual circuits than a 60 amp panel can supply even though the total load will not exceed 60. In order to get the additional over-current devices desired they have to use a 100 amp or larger panel.
How many circuits are connected in your 100 amp panel ?
You may find that in order to have that many breakers, a 100 amp panel is needed.

 

[iwire]

On the other hand, except for photovoltaic or other interactive generation or the simple size of the panel, it is hard to think of a solid reason for doing it?

The designer may know of upcoming changes that the electrician does not.

Another would be the number of circuit spaces available.

I put a 200 amp 40 circuit panel in my parents home but is is supplied with a 100 amp breaker. I did this only to get more circuit spaces.

 

[iwire]

I am somewhat confident that you are not allowed to feed a higher ampacity panel from a lesser one.

As far as the NEC the only issue is that the total calculated load supplied by the 60 amp breaker must under 60 amps. As long as this NEC rule is followed the 60 amp breaker will jot trip from an overload.

 

[kwired]

If you removed the 100 amp breaker and just supplied the main lugs, or changed the breaker to a switch only with no overcurrent protection do you still have any objections to the arrangement? The necessary overcurrent protection is provided by the feeder breaker, you will not have 100 amps or more of current flow without the 60 amp feeder breaker responding to the overload within the trip time curve of that breaker.

 

[jxofaltrds]

Hello everyone,

Honored to be posting my first post here, and it is regarding a drawing I am looking at. The architects are asking for a 60 amp subpanel to be fed from a 60 amp breaker. The new 60 amp subpanel is to feed a 100 amp subpanel with a 100 amp breaker. I am somewhat confident that you are not allowed to feed a higher ampacity panel from a lesser one. I am having difficulty locating why this is so in the code book.

Thank You all for any help that may come.

If I had an AC with a breaker in the panel rated 30 AMPS and used this for a disconnect outside would you have a problem with it? Kinda the same thing.

 

[Dennis Alwon]

If I had an AC with a breaker in the panel rated 30 AMPS and used this for a disconnect outside would you have a problem with it? Kinda the same thing.

[/QUOTE}

:? I see that as the opposite of what the op is asking-- IOW- if the disconnect was 100 amps not 30 amps.. Am I missing something?

 

[jxofaltrds]

If I had an AC with a breaker in the panel rated 30 AMPS and used this for a disconnect outside would you have a problem with it? Kinda the same thing.

[/QUOTE}

:? I see that as the opposite of what the op is asking-- IOW- if the disconnect was 100 amps not 30 amps.. Am I missing something?

He has a 60 AMP feeding a 100 AMP. My example is a 30 AMP feeding a 60 AMP.

 

[Dennis Alwon]

He has a 60 AMP feeding a 100 AMP. My example is a 30 AMP feeding a 60 AMP.

Sorry I thought you were feeding the 30 from the 60.

 

[jxofaltrds]

Sorry I thought you were feeding the 30 from the 60.

Always good to quiz me as my writing style isn't anywhere close to what is in my head. :happysad:

 

[Atlas Shrugs]

Thanks for all the feedback.

I now understand that it is perfectly acceptable to execute the work as originally designed.
However there will be a combined 24 circuits from both panels with room for expansion in the future. I am inclined to believe that recommending an increase to the 60 amp feeder since work has yet to commence would be appropriate here. Keep my mouth closed and install or say something?

 

[kwired]

Thanks for all the feedback.

I now understand that it is perfectly acceptable to execute the work as originally designed.
However there will be a combined 24 circuits from both panels with room for expansion in the future. I am inclined to believe that recommending an increase to the 60 amp feeder since work has yet to commence would be appropriate here. Keep my mouth closed and install or say something?

If competing against other bidders, you probably need to bid as designed, and even if you want to go beyond that design you may price yourself out of the bid.

If not competing, or if adding as an option, then maybe mention any benefits there may be and basically upsell the idea, or even some compromise of installing large enough raceway to accommodate a 100 amp feeder down the road should it be necessary is another idea.