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400a Main breaker fed with 350mcm

M

Mustang125

Member
Location
New Hampshire
Occupation
Master Electrician, Project Manager and Estimator
See attached image. This is showing a 400a main breaker panel fed with 350mcm, wouldn't this need to be 600mcm by code?
See the attached image showing 350mcm feeding a 400a main breaker panel. This seems like it would need 600mcm by code, wouldn't it?

Electric plans.jpg
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Yes the conductors are too small. Is the 400 amp "existing main disconnect" the service disconnect with overcurrent protection?
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Mustang125 said:
The existing main disconnect is a 400a fused disconnect
Click to expand...
So then it looks like the tap rules will apply to the new conductors feeding the nonfused disco from the wireway. Assuming the exiting conductors are 600 they would need to be 600 kcmil since the next size up rule cannot be used.
 
M

Mustang125

Member
Location
New Hampshire
Occupation
Master Electrician, Project Manager and Estimator
I agree. Not exactly sure. We do see disconnects ahead if its 480v service "hot sequence" and no disconnect before "cold sequence" on 208v. But this is a very old install
ptonsparky said:
Who owns the disconnect? POCO would change things.
We would never see a customer owned disconnect ahead of the meter here.
Click to expand...
 
M

Mustang125

Member
Location
New Hampshire
Occupation
Master Electrician, Project Manager and Estimator
the existing conductors leaving the main disconnect into the wireway where everything is tapping off are 500mcm copper
infinity said:
So then it looks like the tap rules will apply to the new conductors feeding the confused disco from the wireway. Assuming the exiting conductors are 600 they would need to be 600 kcmil since the next size up rule cannot be used.
Click to expand...
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Mustang125 said:
the existing conductors leaving the main disconnect into the wireway where everything is tapping off are 500mcm copper
Click to expand...
Then 500 kcmil should have been used instead of the 350's and you don't need the non-fused disconnect after the wireway.
 
kwired

kwired

Electron manager
Location
NE Nebraska
Occupation
EC
ptonsparky said:
POCO may have supplied and own the secondary conductors. Not your problem. Still wouldn't hurt to ask questions because that new 400 you're putting in lowered the demand. Right?:rolleyes:
Click to expand...
I believe he said those are 500's the 350's are feeding the equipment on the right of the diagram
 
kwired

kwired

Electron manager
Location
NE Nebraska
Occupation
EC
infinity said:
Then 500 kcmil should have been used instead of the 350's and you don't need the non-fused disconnect after the wireway.
Click to expand...
The disconnect after the wireway would allow you to disconnect the far right equipment without shutting the entire service down.
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
kwired said:
The disconnect after the wireway would allow you to disconnect the far right equipment without shutting the entire service down.
Click to expand...
The new panels have a main so the disconnect is redundant and not required. It could be used as you've suggested to completely de-energized the new panels ahead of the main CB.
 
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