Reading AMP Draw 230 VAC 1 ph


Thread Starter

Jay Johnston

If a load on an item is rated MAX AMP or FUSE SIZE 40 AMPS, is an amp draw figured on per wire of the 230 vac 1ph load? Or, is the total damp draw 20 per leg which would be 2 x 20= 40 Total amps. Would each leg read 20 AMPS on a 230 VAC 1 PH?

Thank you,
Jay Johnston
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Yes, the rating is stated in terms of per wire, and yes, both wires will read 20 amps or whatever with an ammeter.

See, the amps aren't additive, it's the same 20 amps in both wires. Remember those two wires are the only connection from the load to the power source -- where do the amps flowing in the wire connected to phase A have to go but back up the wire connected to phase B?

It's considered bad electrical etiquette for the electricity to get out of one of the wires and return to the source without coming back through the other wire(s). Three phase works the same way.
Max amp and fuse size usually aren't the same thing, so I am a little puzzled by that. A single-phase 20 amp load will show 20 amps on each of the 2 wires. It is not 40 amps total.