When do parallel installation rules apply?

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TexasMaster

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Lubbock Texas
For example; what articles if any is keeping someone from running 2 200a main breaker sub panels in different locations of a building (100s of feet apart) independently from the lugs of a fused 400a service disconnect. Or would you be required to parallel and "join" it at the other end? Would these be considered feeder taps and the length, being too long, requires you to join it as a parallel feed and tap disconnects from its end and run to panels from there? I've always thought that the parallel is correct but just not sure how to back it up with the nec...
 

infinity

Moderator
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Location
New Jersey
Occupation
Journeyman Electrician
Unless the conductors are connected together at both ends they are not parallel conductors by NEC definition. As you stated if they're separate at one end then the tap rules may come into play. If they're still SEC's then the feeder tap rules do not apply.
 

TexasMaster

Member
Location
Lubbock Texas
Unless the conductors are connected together at both ends they are not parallel conductors by NEC definition. As you stated if they're separate at one end then the tap rules may come into play. If they're still SEC's then the feeder tap rules do not apply.
I apologize.. I think my subject line is misleading. Just not sure how to word it. I understand what a parallel set is and even how to comply with their rules. The better way to put it is; is the stated example correct one way or another and what code articles apply
 

infinity

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No need to apologize. :cool:

In your example two 200 amp panels off of a 400 amp feeder would require that you use the tap rules. If the tap conductors are within the building then the 25' rule would apply. If they're outside of the building then the taps can be of unlimited length. So if the 25' rule {240.21(B)(2)} is applied you would need to keep each set of tap conductors to a maximum length of 25' therefore putting the panels 100's of feet apart won't work unless the tap conductor are run outside.
 

Smart $

Esteemed Member
Location
Ohio
I apologize.. I think my subject line is misleading. Just not sure how to word it. I understand what a parallel set is and even how to comply with their rules. The better way to put it is; is the stated example correct one way or another and what code articles apply
Running 2 x 200A subpanels off a 400A fused disconnect can be done, but if you use anything less than 400A conductors to each subpanel, you have to comply with the tap rules of 240.21(B).
 

GoldDigger

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Placerville, CA, USA
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Retired PV System Designer
Instead of a single 400A disconnect you could use two 200A breakers to supply the two feeders. Might not be economical, but would be compliant.
 

TexasMaster

Member
Location
Lubbock Texas
Instead of a single 400A disconnect you could use two 200A breakers to supply the two feeders. Might not be economical, but would be compliant.

Wish I could. I have an old 400a bucket in an mdp that's already at 6 throws. This 400 is only feeding a 200a sub and I'm into a project needing another 200 amp sub in a different area and working space for gutters and disconnects isn't available in the boiler room/ electrical room of this facility:slaphead:
Thanks to all for the replies. I think I knew it was bad news but worth double checking before I build 400a parallel way out of the way to catch my feed.
 

infinity

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Wish I could. I have an old 400a bucket in an mdp that's already at 6 throws. This 400 is only feeding a 200a sub and I'm into a project needing another 200 amp sub in a different area and working space for gutters and disconnects isn't available in the boiler room/ electrical room of this facility:slaphead:
Thanks to all for the replies. I think I knew it was bad news but worth double checking before I build 400a parallel way out of the way to catch my feed.

If you can run 400 amps worth of conductors to the remote panel the tap rules do not apply.
 

kwired

Electron manager
Location
NE Nebraska
As long as your "subpanels" are in the same building, nothing requires them to have an internal main breaker, so you could use main lug only panels and place the "mains" within a distance from the tap that complies with the tap rules.

I guess such panels wouldn't require an internal main in a separate building either, but in that case the separate building still requires a main disconnect at the separate building, and the panelboard would still require proper overcurrent protection.
 

kwired

Electron manager
Location
NE Nebraska
a 200A CB or fuse block is not all that big. you could put it in a jbox within 10 feet of the 400A disconnect and then there is no tap rule issue.
You still have tap rules and 4 conditions for 10 foot taps that must be met. OP's install likely complies with all 4 conditions though, but condition 3 has not been verified yet - feeder tap must be in raceway - not a cable.
 
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