Feeding two loads from Single UPS 1

[cherry2000]

I have a query..can we feed two panelboards from a single UPS? Each panelboard has a MLO. The UPS outgoung breaker is 600A rated; each panelboard has 250A bus. Please let me know the relevant sections of NEC, and the options available.

 

[rbulsara]

Would you also like your car washed while you wait on one of us?

Please make some efforts of your own to research the Code.
Overcurrent protection for panel boards is very clearly spelled out therein.

Rafiq Bulsara

http://www.srengineersct.com

 

[cherry2000]

That's a good start! Can we use Exhibit 240.7 from the NEC Handbook, and size equal ampacity cables to each PAnelboard (for 600A), and meet the Code?

 

[rbulsara]

That may only be for the feeders. Try little harder for 'panelboards'.

Rafiq Bulsara

http://www.srengineersct.com

 

[cherry2000]

The complete story is : One of the panelboards have an Incomer breaker of 250A. So pulling a cable suitable for 600A ampacity and terminating on this Panelboard is ok. Now the second one is tough..obviously a 600A breaker cannot protect a 250A bus (Sec 408.36). Here a seperate CB of 250A needs to be installed near the Panelboard. Taking the second tap from the UPS should not pose a problem, as long as the cable is sized for 600A. I am not sure about the longest permissible lengths for these two taps from the UPS.

 

[rbulsara]

OK, you are doing well so far. Now check out the tap rules under 240.21 for permissible lengths.

A little hint as a reward for your efforts: Consider installing the 250A CB (or CBs or a sub panel) nearby the UPS (within allowed lengths under the tap rules) and running a feeder rated 250A.

Rafiq Bulsara

http://www.srengineersct.com

 

[waross]

You saved him a few dollars there, Rafiq. LPS

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rbulsara]

Thank you, Bill!

Rafiq Bulsara

http://www.srengineersct.com