I am in charge of reviewing illumination and ITS plans for a roadway project. If any mistakes are found, I adjust them.
The original designer never received the power requirements (from another design firm) in time for the latest submittal of plans i am reviewing. i have since acquired those power numbers.
example: on a branch circuit, I have a single cabinet (nothing else will be added to the circuit) that needs 600 W of power. By using 120 volts on the service, I know that the current necessary is 600/120=5 amps. The designer, not having this information, went conservative and decided to design for a current of 20 amps. The electrical service ordered used a KVA load and branch circuit load based on 20 amps, but what is really needed is 5 amps.
I am not familiar enough in electricity and services so i have the following questions:
i know the branch circuit only needs 5 amps, but 20 is provided. So long as the conductor sizes can carry the load safely, is the design safe and conservative? Or is the extra amps (15 more than required )dangerous to any of the equipment?
Does the electrical service need to be altered at all for this to work properly, assuming it was designed with a higher KVA load due to the 20 amps? In other words, reducing the amps means reducing the KVA load necessary
is there anything in the NEC that states the branch circuit must equal what is necessary for the device to work?
is it possible to adjust the branch circuit from 20 amps to 5 amps after the service has been ordered? Switching to 5 amps (while maintaining the breaker size from the 20 amp design) would help tremendously with conductor and conduit sizes, but I'm not familiar enough with a service to know if the circuit and KVA load can be adjusted.
if so, what is the time frame?
I feel like I know enough to be dangerous. I can provide any more information regarding the design as needed if its not clear.