Detached Shop Sizing Feed

[Nif@Home]

100amp panel in detached shop 340-feet from main breaker panel @ house (buried UG PVC conduit raceway)

My largest loads will rarely be used non-concurrently and only for short durations:

• Tankless H2O (240V, 70a) - the voltage drop killer serving one sink and shower that will rarely be used
• Welder (240V, 50a) - also just hobby welding so a tack here a short bead there
• Air Compressor (240V, 30a) - Maybe some painting
• Car Lift (240V, 20a) - 1 min up/down

All other load is just small hand tools and LED lights.

If I assume 83% (NEC 310.12) amperage (83amps) for residential this requires 2/0 CU (4/0 AL) conductor for voltage drop.
If I assume 80% load to the H20 and bath circuit simultaneous load (72a) I drop to 1/0 CU (3/0 AL).
This still seems HUGE given the loads are so transient that the conductor will likely never heat up.

Given these knowns, LOL and spending your own money, what would you use? Neutral size too?

 

[Little Bill]

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