Wire Size

[Alwayslearningelec]

Perfect scenario as I'm currently taking the MH calculations course.

If I DID NOT have the mechanical nameplate/equipment schedule data info could I still size the wire off ONLY the breaker size?
I would assume the order is this in design?

1. Select the equipment.
2. Size the breaker.
3. Size the wire from the breaker size?

 

[augie47]

You normally determine the load (on HVAC this would be nameplate, on motors Art 430 FLA), select the conductor to feed that load (taking into account adjustments for fill, ambient, etc) and then select the breaker to protect the conductor and load.
If you don't know the load the you can base the conductor on the breaker size as you suggest. (Occasionally that will bite you when you find the actual load or you may find the conductor is oversized but it's done every day.)

 

[Alwayslearningelec]

You normally determine the load (on HVAC this would be nameplate, on motors Art 430 FLA), select the conductor to feed that load (taking into account adjustments for fill, ambient, etc) and then select the breaker to protect the conductor and load.
If you don't know the load the you can base the conductor on the breaker size as you suggest. (Occasionally that will bite you when you find the actual load or you may find the conductor is oversized but it's done every day.)

Thank you. So essentially your working backward....load, wire, breaker .