When would you use 14 AWG, please? (Or another way to ask the same question: What type of circuits would be 21 - 30 A, as per R57, pg. 87?)
Size of the breaker on the PDB power distribution board determines wire size requirement.
Thank you. Based on your experience, have you ever used the 30A circuit? If so, what was hooked up to it? We haven’t yet and are wondering just what would be used there?
Well, you have to use 12 gauge with anything hooked up to a 40A breaker. Everything else though could easily be 14 gauge. Even if you’re putting a 20A breaker on it, I think it’s worth using 14 gauge wire. That gives you the flexibility to up it to 30A if you start tripping the breaker, without needing to rewire the robot.
Oh, so you oversize the gauge of the circuits that have a smaller gauge requirement? Is that correct?
Yes. You’re allowed to exceed the gauge requirement in size, just not go under it. A thicker wire will have less resistance anyway. The only real penalty is that thicker wire is slightly heavier, so if you’re close on weight it can be an issue, but this is a fairly small edge case.
Yes, you can always go larger wire safely. Don’t overdo it, but going up a size for a circuit does give more flexibility, and it’s safer to a degree. However, make sure your connector can accept the larger wire. You never want to remove strands of wire to get it to fit properly into a connector.
Great! Thank you all, so much.
Still one nagging question, though… What type of circuits or components use 30 A?
For instance, any of the motors that draw from 21 to 30amps would be candidates, like the snow blower motor.
Any motor with a maximum draw less than 20a (like the throttle motor), and most custom circuits could use a 20a breaker.
Any motor drawing more needs to be on a 40a breaker.
Although, you can go over the breaker limit for short amounts of time, and if your usage is not stressful you can sometimes get by with a lesser breaker.
2017-motor-information.pdf (222 KB)
2017-motor-information.pdf (222 KB)
Per R56, only motor controllers and custom circuits may use breakers larger than 20A. Note that you can put two smaller motors on one controller which may be useful for “doors” or light duty intakes/feeders that may come to fit on a 30A breaker.
It’s tough to imagine what custom circuit would require 30A, unless it was really a bunch of different items on breaker.
Thanks. and thanks for the reference.
Thank you, it helps round out our thinking of what we were wondering about.
Also once you are over 8 motors on your 40A breakers you have to start moving them down to 30A breakers. So we wire MiniCIMs and 775pros to 30A breakers all the time. Basically motors 8-16 on any robot have to be on 30A or 20A breakers.
We normally wire all of our motors with 10 or 12 AWG wire just encase we need to swap them to a larger breaker. Then most of our smaller gauge items are wired with 18 AWG. This keeps things simpler.
Ah, that’s why it hasn’t yet come up for us: we have never run out of 40A breakers yet, but this is great to know. We took the advice and got 10 AWG for all the great reasons mentioned. Thank you.