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jay_haitch

help me with my subpanel planning & calculations

jay_haitch
15 years ago

A hearty thanks to any who can give me advice on my decision making.

The Prologue: 2 year old house. I want to add a subpanel for basement workshop, subpanel for attached garage, and have things ready to run another sub to a future detatched garage. I spec'd 400 amp service when we built, despite the calculations coming up with 178 amps, so I have lots of extra overall capacity as I wanted.

The details:

Basement workshop to have 3000w saw, 2200w dust collector, 1000w lights, 400w air filter, two 15 amp general receptacle circuits for 9600w gross load.

Attached garage: 5000w unit heater, 1500w lighting= 6500w or 27.1 amps.

Future detached garage: 4 car, so CEC requires 15 amp circuit per bay, plus outside plug, plus general lighting and garage door opener circuit, which I assume must be a separate one. Therefore 1500w each x 6= 9000w or 37.5 amps.

My question is how best to feed this all. I could run 1"conduit (with 3/0 copper x2, plus #8 neutral and #6 ground based on current CEC) from the service panel to the basement workshop, same again from workshop to attached garage, and then 8/3 to the future detached garage. But this means conduit and stiff individual wire.

My other choice is to run 8/3 with 40 amp breaker from service panel to basement workshop, then run 6/3 with 60 amp breaker from service panel to attached garage, and same again to future detached garage.

Which of these is the best? Anyone have other options? Cost isn't the main thing, doing it right with the least future possible complications/regrets is.

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