Long run to sub panel

[electric-ed]

For voltage drop calculations, the CEC has Table D3, which can be difficult to use.

For a load of 20 amps (at 240 volts) at a distance of 75m, #8 would be required to limit voltage drop to 3%, which is the recommended amount. (Rule 8-102)

#10 would result in a somewhat higher voltage drop, which you may be able to tolerate.

Even if you used the #8 you would still have some light dimming when starting a good sized motor, such as a compressor.

My shop is about the same distance, and I'm thankful now that I ran three # 6 TWU in black poly pipe, as I am able to use my welder in that location.

Ed

[Ellement]

I would like to supply power to a remote garage that will supply general lighting and a few outlets (maybe 4 single pole circuits total).

The distance from main panel to the remote sub panel is approx 75m. I would like to know if I de-rate the wire by installing a 20 amp breaker in the main panel to supply a 10/3 NMWU to the sub panel if this would be OK?

If not what would you suggest? I tried to find a formula in the CEC to calculate the wire size to distance to load demand but couldn't find anything straight forward.
I suspect the voltage drop will be most prominent on high current demand like a motor or compressor start up, how will it be possible to accommodate these demands without incurring a substantial wire expense?

All your opinions are welcome. Thanks