Busway System

Kidd

Member
Location
Texas
Hey gents,

so i have a question about a busway system I'm designing. I dont do a whole lot of designs for busways so i want to make sure I'm not missing anything.

I have a 5000 amp, 480v service going to a 15 story condo/apartment. The main switchgear is located on the south side of the building at floor level. the electrical rooms for each floor are located on the north side of the building and start on the 5th floor. The first floor has a main entrance area, with one half being office/lobby area and the other half being parking. The second floor is split the same way with a staff office/break area on one side and the other half is parking. the 3rd and 4th floor is all parking and then the rest of the building is apartments/condos.

I'm planning on running a 4,000 amp feed with pipe and wire from the switchgear over to the south side of the second floor and placing a tap box on the second floor (directly under the where the electrical rooms are) that will feed a 4,000 amp vertical busway. the vertical busway will go from the tap box straight up through every floor going through the 3rd and 4th floor parking garages and then hitting the electrical rooms in floors 5-15.

My feed at the main switchgear will have gfi protection since it's over 1,000 amps. At each electrical room, I'll have three fused disconnects with current limiting fuses to help bring down the fault current since it was pretty high.

two things I'm not 100% sure of -

When I'm transitioning over from pipe and wire to the busway. I dont believe I'm required to have a disconnect, or if I'm ok with just a tap box. I have ocp at the switchgear, but I'm not sure if a disconnect would be required on the second floor. I dont think so, because it's not really a tap right? it's all just one big feeder?

The busway will be all vertical and pass through 2 floors that are parking garages, but I'm not sure this is allowed. Section 368.10(A) states "Busways shall be permitted to be located in the open where visible ....." So i believe we're good there, but then section
368.12(a) states Busways shall not be installed where subject to severe physical damage or corrosive vapors"
Would a parking garage be an area where it could be subject to severe physical damage, say if a car hits it? The busway would be against a wall, that cars would have to circle around, so there is a possibility that a reckless driver could hit it. If this is an issue, could i get away with installing pipe bollards, or would i have to build a wall/room around the busway?

Thanks for any input guys, i really appreciate it!

Thanks!
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Tap boxes that simply transition from pipe and wire to the busway do not require anything special. If the busway is in a damp location then it would need to be listed for damp locations. Running exposed in a parking garage is not permitted when subject to sever physical damage. IMO getting hit by a motor vehicle would qualify as meeting sever physical damage so something would need to be done to mitigate that possible damage.
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
If pipe bollards are used I think guard rails should also be attached in front of them to deflect errant vehicles away from the busway area.
 

Todd0x1

Senior Member
Location
CA
Look at the amount of time that building (that people live in) will be dark when someone hits the busway in the garage. Even if not required I would make sure someone could crash a large SUV into it at above normal garage speeds and not damage the busway. Is the wall the busway is against cast concrete? I don't know how deep the busway is, and am not an engineer, but maybe something like vertical members of rectangular tube bolted to the wall on either side of the busway, horizontal crossmembers spanning those, then a bolted on cover steel plate covering everything. Seems like a few thousand well spent. And dams at floor penetrations of course and other water protection where needed. Had a busway in a garage burn down due to water leaking onto it from above, was inspected and IR annually but no one noticed the top all rusted out until that final drop of water did its job. It had a drip tray over most of it too, but the water was running down a wall the busway passed through.
 

Kidd

Member
Location
Texas
Thanks for yalls input.
Just a few comments
- the tap box is in an open office area so no need for the dam/wet location rating
- the busway is the pow r way iii that comes fully enclosed and has fittings for outdoor areas.
- the wall the busway runs up is the wall on the outside of the elevator shaft that runs up the entire building.
- the busway is about 18” deep.

so it sounds like at minimum, I’ll be adding pipe bollards and a guard rail (good idea on that one). But your set up to have it enclosed is what I’ll try to pitch, it sounds like a better option

thanks guy!
 

Todd0x1

Senior Member
Location
CA
I was talking about dams where the busway passes through the garage levels in the event of a leak or sprinkler activation.
 
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