Branch Circuit Question

T

Travis C

Member
Location
VA
Occupation
Controls Electrician
I have been asked to run a circuit that is part of our automatic transfer switch and emergency generator backup. This circuit will contain 6 IT switches that are plugged into 6 uninterrupted power supplies. Each of these UPS are rated at 9.2A maximum load and are suggested to be placed on a 15A breaker. Total load of this circuit would be 55.2A which would size my breaker at 60A for the circuit. My thought is to run 60A wire to the top of a disconnect for each of the six UPS. I would then fuse that disconnect with a 15A fuse. To continue the circuit from each disconnect, I would use one that had multi lugs on the line side. Unfortunately, there is around 250 feet of distance from the furthest UPS to the breaker panel which would require me to use 1/0 wire for the branch circuit. Is my plan the way to proceed, or should i split the load into multiple circuits? If you have any advice i'd love to hear it. Thanks.
 
Travis C said:
I have been asked to run a circuit that is part of our automatic transfer switch and emergency generator backup. This circuit will contain 6 IT switches that are plugged into 6 uninterrupted power supplies. Each of these UPS are rated at 9.2A maximum load and are suggested to be placed on a 15A breaker. Total load of this circuit would be 55.2A which would size my breaker at 60A for the circuit. My thought is to run 60A wire to the top of a disconnect for each of the six UPS. I would then fuse that disconnect with a 15A fuse. To continue the circuit from each disconnect, I would use one that had multi lugs on the line side. Unfortunately, there is around 250 feet of distance from the furthest UPS to the breaker panel which would require me to use 1/0 wire for the branch circuit. Is my plan the way to proceed, or should i split the load into multiple circuits? If you have any advice i'd love to hear it. Thanks.
Click to expand...
If I understand correctly that would result in the outputs of the UPS units being connected to each other. I don't think you want to do that.
 
ggunn said:
If I understand correctly that would result in the outputs of the UPS units being connected to each other. I don't think you want to do that.
Click to expand...
Each UPS feeds one switch. This would be wired in parallel so that each tap is individual to that UPS.
 
I cringe at the thought of doing this. That many small UPS systems introduce that many more points of failure, not to mention the care and feeding of all the batteries (which a LOT of people completely forget about until it's too late). Figure out how much power the switches could consume at full load, then get a single UPS to match.
 
ModbusMan said:
I cringe at the thought of doing this. That many small UPS systems introduce that many more points of failure, not to mention the care and feeding of all the batteries (which a LOT of people completely forget about until it's too late). Figure out how much power the switches could consume at full load, then get a single UPS to match.
Click to expand...
 
ModbusMan said:
I cringe at the thought of doing this. That many small UPS systems introduce that many more points of failure, not to mention the care and feeding of all the batteries (which a LOT of people completely forget about until it's too late). Figure out how much power the switches could consume at full load, then get a single UPS to match.
Click to expand...
I like your idea, but I don't believe I will be getting a say in how they run the IT department. I would still be left with the dilemma of running power to multiple switches with one being 250' away.
 
Travis C said:
I like your idea, but I don't believe I will be getting a say in how they run the IT department. I would still be left with the dilemma of running power to multiple switches with one being 250' away.
Click to expand...
9 amps run for 250' at 10AWG still leaves you at ~115 volts, according to Southwire. Given that switches are generally 100-240 natively or use a wall-wart (that itself is usually 100-240), voltage drop shouldn't be a concern.
 
ModbusMan said:
9 amps run for 250' at 10AWG still leaves you at ~115 volts, according to Southwire. Given that switches are generally 100-240 natively or use a wall-wart (that itself is usually 100-240), voltage drop shouldn't be a concern.
Click to expand...
Yes, but I have six UPS that I need to feed from one circuit. That would bring me to 55.2A for the branch circuit. From the disconnects to the UPS I can run a smaller gauge wire as it only needs to be rated for over 9A. I am starting to think my best bet would be to run two circuits to subpanels and branch out from there.
 
Travis C said:
Yes, but I have six UPS that I need to feed from one circuit. That would bring me to 55.2A for the branch circuit. From the disconnects to the UPS I can run a smaller gauge wire as it only needs to be rated for over 9A. I am starting to think my best bet would be to run two circuits to subpanels and branch out from there.
Click to expand...
No, you have six switches that need UPS-conditioned power. Flip the thinking around, especially if you're already considering using a sub-panel to branch out. As I said earlier, six individual UPS units might make the IT crew happy, but it's more unreliable than a single unit. Even Vertiv says so, and they have a vested interest in selling more stuff.
 
You must log in or register to reply here.
Top