sub-panel disconnect

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derease

Member
I ran a sub-panel to a garage that is 25 feet from the main residence. It is a 100 amp sub-panel with 16 spaces. It is a lug panel with the main breaker in the residence at the main panel. my question is do I need a disconnect (main breaker) in the sub-panel? I already missed having a grounding rod for the sub and don't want to miss anything else. Any advise would be appreciated. Thanks Dave
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
How many breakers are being installed in the sub-panel ?
If more than 6, you need a main in the panel.
The sub panel must comply with 225.21 nad 225.36
 

charlie b

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Location
Seattle, WA
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Electrical Engineer
To be more precise, there must be a way to disconnect all power from the garage, and it has to be local to the garage. The breaker in the house panel will not suffice. The easiest way to achieve this is to have a main breaker in the garage panel. But that is not the only way. A non-fused disconnect outside the garage is another option.
 

Dennis Alwon

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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Dave, be careful if you use a MLO panel and install a main breaker then you will have to use a retainer clip for the main.

408.36(D) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel.
 

derease

Member
There is a square d panel in the garage (lug panel). Can I just add a 100 amp breaker inside the panel to feel the bus bars?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
You can. If you are using a branch breaker spot be sure to heed Dennis' advice on the retainer clip.
 

haskindm

Senior Member
Location
Maryland
How many breakers are being installed in the sub-panel ?
If more than 6, you need a main in the panel.
The sub panel must comply with 225.21 nad 225.36

I many areas, if the panel has the capacity for more than six breakers a disconnect will be required. Any other words, if I only install 4 breakers in a 40-circuit panel, the AHJ in this area would require a disconnect. If I install a 6-circuit panel, they would accept it and no additional disconnect would be required.
 

roger

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Location
Fl
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Electrician
I many areas, if the panel has the capacity for more than six breakers a disconnect will be required. Any other words, if I only install 4 breakers in a 40-circuit panel, the AHJ in this area would require a disconnect. If I install a 6-circuit panel, they would accept it and no additional disconnect would be required.

What do these inspectors do if you have to supply a load requiring 70 amps with a fusible disconnect?

Roger
 

roger

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Location
Fl
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Electrician
To the wire, did you run 3 conductor with ground? If you did I believe there is no need for a ground rod.

The GES is required, read 250.32 taking note of the first sentence of 250.32(A)


Roger
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I many areas, if the panel has the capacity for more than six breakers a disconnect will be required. Any other words, if I only install 4 breakers in a 40-circuit panel, the AHJ in this area would require a disconnect. If I install a 6-circuit panel, they would accept it and no additional disconnect would be required.

So you install a six circuit panel or 12 circuit panel--- suppose I want 6 DP breakers as my disco. Here's the problem. I install 4 dp and have space left for 2 more DP or 4 sp---- then what do you do. :)
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I install 4 dp and have space left for 2 more DP or 4 sp---- then what do you do. :)
Nothing; it's not my issue.

What, me worry?
newman.jpg
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
. . . im not understanding why i cant just run a 4-wire and no groundrod at the garage
Because, unless the supply is a circuit (single or MWBC), the separate structure is required to hane an electrode system.

In a nutshell, a separate structure fed by a feeder is wired like a service as far as grounding is concerned, and like a sub-panel as far as bonding is concenred.
 
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