120 volt circuit in 480 volt switchboard

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jimingram

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Location
St Paul MN
A new scoreboard for the soccer field was donated to the private school my children attend. It draws 3 amps at 120 volts. There is an empty conduit from the MDP I want to use to get into the building. The conduit is conveniently located near the soccer field. It was meant to be used for future lighting.

My concern is running a 120 volt, 20 amp multiwire circuit through this 480 volt switchgear. The engineer must have thought any outside ligthing would have 480 volts. Specifically I plan to install a 10-3 UF cable close to the available conduit. I assume the UF cable would not be permitted to enter the switchgear. I would make install direct burial cable through the underground conduit, unspliced through the switchgear, and then through a new conduit to a 120/208 volt panel. I would install a junction box to splice the two sets of water together outside the building.

I would appreciate your thoughts.

Jim Ingram
 

tom baker

First Chief Moderator
Staff member
See 300.3(C)(1) for the 120 and 480 together.
If your circuit to the scoreboard is conduit - use XHHW-XLP instead of the UF. UF in a conduit is, well, cheesy.
As far as the 120 volt circuit in the 480 panelboard see 312.8 for wire fill.
If you are under the 2011 NEC there is a new requirement for feed thru conductors in 408.4(B) you will have to comply with.
 

tom baker

First Chief Moderator
Staff member
One more comment if the new scoreboard is at the back of the ball field, have you looked at voltage drop?
I did a scoreboard once and fed it with 480 and then used a mini power zone to get the 120V
 

jimingram

Member
Location
St Paul MN
To be more specific, the UF cable will be installed to the side of the soccer field in the ground. There is a 3" PVC conduit from the switchgear to an area near the soccer field that I can use to get into the building.

I'm also aware of the voltage drop.

Thanks for your input.

Jim
 
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