Best way to feed massive RTU loads for a 3 story building

[theophilus88]

I am currently working on a giant rec hall/ concert venue/ arena style building. Due to the large space, we have massive RTU loads which need to be fed from a main distribution panel 3 levels below in the basement. There is currently 8 RTU's all at about 140A's, 480V, 3PH each. Would it be better to feed these RTU's straight form the MDP in the basement, or provide a mechanical panel on the roof which can support these heavy loads? Keep in mind, since I'm in the design build industry, I need to keep the cost down as well. Is there a big cost difference between running that many large feeders 3 floors vs 1 large feeder and a panel? Any help would be much appreciated. Thanks in advance!

 

[Npstewart]

I am currently working on a giant rec hall/ concert venue/ arena style building. Due to the large space, we have massive RTU loads which need to be fed from a main distribution panel 3 levels below in the basement. There is currently 8 RTU's all at about 140A's, 480V, 3PH each. Would it be better to feed these RTU's straight form the MDP in the basement, or provide a mechanical panel on the roof which can support these heavy loads? Keep in mind, since I'm in the design build industry, I need to keep the cost down as well. Is there a big cost difference between running that many large feeders 3 floors vs 1 large feeder and a panel? Any help would be much appreciated. Thanks in advance!

Feed them from the MDP. If you feed it from a new panel then you’re just providing larger infrastructure to carry the load around the building. If it’s only 3 floors then probably not a very long run per unit.


Sent from my iPhone using Tapatalk

 

[Npstewart]

Feed them from the MDP. If you feed it from a new panel then you’re just providing larger infrastructure to carry the load around the building. If it’s only 3 floors then probably not a very long run per unit.


Sent from my iPhone using Tapatalk

Also, I would probably consider having a dedicated run from the transformer to a separate MDP for the rooftop units. Maybe a 1200 or 1600A MDP just for mechanical “MMDP”.


Sent from my iPhone using Tapatalk

 

[zbang]

I kinda sounds like costing it both ways-
On one hand, no intermediate panel to install; OTOH you can possible use less copper with smaller feeders (via demand factors) and less voltage drop concerns in the branch circuits. Heck, if the RTUs are spread around, you might use two mechanical panels instead of one and site them closer to the units.

 

[JoeStillman]

8 runs of (3) # 2/0 @133.1 kCM = 3194 kCM of CU vs. 3 runs of (3) 600 kCM = 5400 kCM of CU plus the cost of a 1200A breaker and panel, and you still need a couple of hundred feet of 2/0.

I'd go with the 8 runs. You can go a mile with 480 to a 460V unit.

 

[petersonra]

run 4160 upto the roof and put in transformers there for the RTUs.

 

[topgone]

Run a feeder up to the location of the large RTUs and install your transformer there. It is cheaper running MV and then stepping down to the utilization voltage at the final load location. I have done a project like that (8 X 80ton RTUs using separate 2 X 500 kVA transformer feeders).