How To Run 60 Amp Service To Garage

Question

There'southward little to add to ThreePhaseEel's excellent reply. Simply hither are a few thoughts.

Aluminum wiring

I recognize the "Aluminum wiring is good" statement can be hard to take given 30 years of retrofitters whipping people into a barm about aluminum pocket-size-appliance circuit wiring. There is a asset of truth there.

Back in the 1970s there was a copper shortage. Aluminum actually has nearly twice the conductivity of copper by mass and 12 times the conductivity by dollar, which makes 1350 blend the darling of power companies. Wire companies who make both said "Hey, nosotros could simply put house-wire insulation on 1350 blend, merely use the next size larger (-2 numerically)" because aluminum has less conductivity by volume. Given the urgency of the shortage, this was rushed through, including rushing through UL listing of essentially copper-rated terminations. This became a problem on small branch circuits <=30A, which is eighty-ninety% of the circuits in a house.

Turns out aluminum and copper's different thermal expansion ratios mean over many thermal cycles, copper terminations shell and deform aluminum wire, loosening the clamping force. That, plus oxidation, causes trouble. The reverse is not truthful; aluminum terminations are perfectly resilient on copper wire.

Now, bored electricians whip the public into a froth about aluminum branch-circuit wiring, considering rewiring a whole firm is a slap-up gig if you can go information technology. But instead you can utilise CO-ALR rated ("R"=revised) receptacles/switches, pigtail with Alumiconns (lug terminals fabricated of aluminum, meet higher up), or AFCI breakers come up to the rescue, by detecting the master trouble - arc faults. Also, a new AA-8000 blend was formulated specifically for in-firm wiring. You could wire a new firm today with CO-ALR receptacles and AA-8000 (if you could observe anyone who stocked it in pocket-size sizes).

However, nobody's e'er disputed that aluminum wires (fifty-fifty 1350) were always prophylactic for larger feeder connections (4AWG and larger). Nonetheless 1350 is banned and they should sell you AA-8000. Employ the No-Ox goop, and tighten to torque spec.

Voltage drib

In that location's another bit of oogabooga about "voltage drib". Lawmaking says null nigh 3%, but somehow that number has been finer ..... marketed.

That was e'er incorrect. It was always intended every bit a "rule of thumb", and fifty-fifty and so, information technology was meant to be applied to the routine daily/continuous load non occasional loads and certainly not the breaker rating. And and then, it became a lot wronger with computers. Trouble is, people do this:

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and that's the default for Pete'due south sake! What'due south wrong with that? I encounter a huge number of cases where I override the number and looks what's hiding backside the pall:

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Oh, come on. And like I say, I get a 3.01-3.60% number on well over half the calcs I practice. Calling for a bump in these cases is certainly non the intent of the 3% rule-of-thumb, heavens no!

Your bodily loads

Once again, voltage drib calcs should be based on your typical loads when active, never your circuit breaker rating. You're expecting 47A @ 120V, which ways ideally 23.5A @ 240V (but more than cynically, say 17 and 30A, with 13A on the neutral).

For 240V circuits, information technology isn't fifty-fifty worth checking the voltage drop calc for <115', merely 30A on a 60A circuit, fuggedaboutit.