Leave extra wire in conduit for future expansion

Question

Quick question that's come up when wiring a garage/workshop. I ran 3/4" conduit, and in one length I'm planning to run 3+1 10 AWG for a 240V/30A circuit, as well as 2+1 10 AWG for a 120V/20A circuit. I've intentionally oversized the 120V/20A circuit as I'd like the option of upgrading to a second 240V circuit in the future. If I ever did that, I'd obviously need an additional hot wire. I know that I could leave a pull string, but is there any issue with simply pulling an extra wire now, and leave the ends capped with wire nuts in the sub panel and a junction box?

Thanks.

EDIT for additional details: It is EMT. And this is actually coming from a subpanel. I ran a 60A sub to my (attached) garage, and am now wiring these circuits from that sub. So it's actually a short run of wire, and leaving the extra wire is a negligible cost.

Answer 1

There is no problem having unused conductors, properly capped, in your circuit. Since you'll total 8 wires you're within fill capacity for 3/4" conduit (10 or 11 depending on type).

You might ask yourself whether a 60A or 100A sub-panel isn't a better strategy, though. Four aluminum wires might be cost-equivalent to the copper you're planning and you'd have many more future circuit options.

Answer 2

Given that you're already feeding from a 60A sub, I double-down on isherwood's advice and say: Continue onward with 60A wire from that sub to a new sub here. Attach this wire to that sub simply by "Tee"-ing off the feed wires coming into that sub. Yeah, you can do that.

Note that in THHN/conduit, there is no such thing as a 60A circuit; your choices are #8 for 50A or #6 for 65A, but in the latter case you are entitled to "round up" to the next available breaker size: 70A.

If it's EMT the whole way, then dump the ground wires. Don't need 'em. Even if it's PVC, you only need 1 ground wire shared by all circuits.