OCP for sub-panel

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smallfish

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In a dwelling, a 200-amp disconnect is installed at the nearest point of entry because the panel is to be located on an inside wall. The feeder panel is a 200-amp, 40-circuit main lug only panel. A 100-amp main lug only 24-circuit sub panel is fed from it and is located immediately adjacent to it. Is overcurrent protection required for the 100-amp panel?
This will be one of several forum questions whose answer I want to be sure of. Thanks.
 
smallfish said:
In a dwelling, a 200-amp disconnect is installed at the nearest point of entry because the panel is to be located on an inside wall. The feeder panel is a 200-amp, 40-circuit main lug only panel. A 100-amp main lug only 24-circuit sub panel is fed from it and is located immediately adjacent to it. Is overcurrent protection required for the 100-amp panel?
This will be one of several forum questions whose answer I want to be sure of. Thanks.
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You really got me thinking with that question. :)

After a quick review of the tap rules I think you have to provide over current protection for the 100 amp conductors that are feeding it.
 
Here is a twist for your question, how many circuit breakers are going in the 24 circuit panel ? If you have "One" 200 amp main and "Five" handles or less in the 100 amp panel, you are less then Six throws, and they are grouped.
It would be a really cheezy install but it would comply with 230.71
 
smallfish said:
In a dwelling, a 200-amp disconnect is installed at the nearest point of entry because the panel is to be located on an inside wall. The feeder panel is a 200-amp, 40-circuit main lug only panel. A 100-amp main lug only 24-circuit sub panel is fed from it and is located immediately adjacent to it. Is overcurrent protection required for the 100-amp panel?
This will be one of several forum questions whose answer I want to be sure of. Thanks.
Click to expand...

Looking at this question again, is there any OCP or is this just a 200 amp Non fused disconnect ?
 
smallfish said:
In a dwelling, a 200-amp disconnect is installed at the nearest point of entry because the panel is to be located on an inside wall. The feeder panel is a 200-amp, 40-circuit main lug only panel. A 100-amp main lug only 24-circuit sub panel is fed from it and is located immediately adjacent to it. Is overcurrent protection required for the 100-amp panel?
This will be one of several forum questions whose answer I want to be sure of. Thanks.
Click to expand...

If I'm reading your question correctly, you are saying that the 100 amp panel is being feed from the 200 amp panel, not the feeder feeding the 200 amp panel? correct? If so, are you not installing a breaker in the 200 amp panel for the 100 amp MLO feeder? Properly sized for the panel and wire of course, then you already have your OCP for the 100 amp MLO panel. Or are you using feed through lugs or some other means to tap off the 200 amp feed?
 
I realize that the question that I posed, begs questions itself. I'm sorry that all I have is the wording of the question and nothing more.
 
smallfish said:
I realize that the question that I posed, begs questions itself. I'm sorry that all I have is the wording of the question and nothing more.
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Who wrote the question, It sounds like it was translated from another language and lost some important information in the process.
 
smallfish said:
I realize that the question that I posed, begs questions itself. I'm sorry that all I have is the wording of the question and nothing more.
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No pun intended, smallfish, but we're kinda like pirhanas here. :D We keep posting until nothing but bones are left.
 
smallfish, it seems nothing in the NEC is ever real simple.
There are some varibles that might effect the answer to your question, among them, wheather the panel is classified as a lighting and applliance panelbord and then only if that was prior to the '08 Code as '08 eliminated L&A panels.
Keep in mind the primary consideration is to protect the panel (100 amp buss) and the wire feeding it.
There might be some situations where you would not need a breaker ahead of the panel, but they would be rare. In actual practice, you would normally install a breaker in the main panel to protect tye sub-panel and feeder.
 
smallfish said:
In a dwelling, a 200-amp disconnect is installed at the nearest point of entry because the panel is to be located on an inside wall. The feeder panel is a 200-amp, 40-circuit main lug only panel. A 100-amp main lug only 24-circuit sub panel is fed from it and is located immediately adjacent to it. Is overcurrent protection required for the 100-amp panel?
This will be one of several forum questions whose answer I want to be sure of. Thanks.
Click to expand...
Since the feeder panel is MLO, presumably this means the disconnect has an OCPD in it.

Normally one might expect the subpanel to be fed from a 100A breaker in the feeder panel.

If you are running feedthrough w/o going through a breaker in the feeder panel, the conductors going to the subpanel would need to be sized for whatever OCPD is in the 200A disconnect.
 
smallfish said:
In a dwelling, a 200-amp disconnect is installed at the nearest point of entry because the panel is to be located on an inside wall. The feeder panel is a 200-amp, 40-circuit main lug only panel. A 100-amp main lug only 24-circuit sub panel is fed from it and is located immediately adjacent to it. Is overcurrent protection required for the 100-amp panel?
This will be one of several forum questions whose answer I want to be sure of. Thanks.
Click to expand...


This sounds like the classic example of a subpanel supplying another subpanel.

The 100 amp subpanel does need some type of OCPD on its supply side as per 408.36



The one question that begs answering is:
How have you supplied the 100A panel? -from the 200 amp panel via a 100A circuit breaker? or -from the 200A panel via the bus without a 100A OCPD?
 
smallfish said:
In a dwelling, a 200-amp disconnect is installed at the nearest point of entry because the panel is to be located on an inside wall. The feeder panel is a 200-amp, 40-circuit main lug only panel. A 100-amp main lug only 24-circuit sub panel is fed from it and is located immediately adjacent to it. Is overcurrent protection required for the 100-amp panel?
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I say yes, as you phrased the question. The only way around it would be to replace the 200a main with 100a OCP.
 
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smallfish said:
Is overcurrent protection required for the 100-amp panel?
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I removed all other words from your post, when I captured the quotation above, because no other words matter. Yes, a panel requires overcurrent protection. Period. End of story.

As a separate matter, we can get into what the question's author was trying to ask, or what the author thought he or she was asking. But that is what was actually asked.

Perhaps the question's author was attempting to get into tap rules, or into using one breaker on the main panel to protect the sub-panel, or into the six handle rule. But no words in the question, as written, lead us down any of these paths. Perhaps the author wanted us to figure out how this particular sub-panel is being protected in this scenario, or figure out whether this scenario actually does provide adequate protection for the sub-panel. But no words in the question, as written, call upon us to address these questions.

Bottom line: it's a badly worded question.
 
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