Does NEC 445.13 require generator conductors to be sized at 115%?

Often yes. When the generator does not have overcurrent protection integral to the machine, NEC 445.13 commonly drives the conductors to the first distribution device to at least 115% of the generator nameplate current, but the equipment listing and exact arrangement still matter.

What voltage-drop target is reasonable between a generator and transfer switch?

A practical target is about 2% to 3% on the generator-to-transfer-switch run so the total path stays near the familiar 5% design guidance once feeder and branch-circuit losses are added downstream.

Can a generator circuit pass ampacity and still fail in the field?

Yes. A 22 kW, 240V standby generator draws about 91.7A at full load. On a 200-foot run, a conductor that barely passes ampacity can still leave too much voltage sag when a 40A well pump or 60A HVAC compressor starts.

Should I size the generator feeder from the transfer switch breaker?

No. Start with generator nameplate current, equipment instructions, NEC 445 and NEC 702 requirements, then check route length and motor-starting conditions. Breaker size alone does not describe the generator source impedance or the voltage-drop risk.

Is aluminum acceptable between a standby generator and ATS?

Yes, aluminum is often economical on longer outdoor runs at 100A and above, but copper can be the better answer where the run is marginal, the environment is corrosive, or the load mix includes high inrush motors that need tighter voltage control.

What other pages on this site help with backup-power wiring?

Run the wire size calculator first, then compare generator work with the detached garage feeder guide and the well-pump wire-sizing article if the standby system must carry long feeders or heavy motor loads.