Electrical connection between cut off switch and power distribution board

The rule book says that 6 gauge insulated wire should be used for this connection.

Can an insulated bus-bar be used for this connection instead? :confused:

Good question. The relevant rule appears to be:

*R38 The ROBOT battery, the main 120-amp (120A) circuit breaker (Cooper Bussman P/N: CB185-120), and the Power Distribution (PD) Board shall be connected as shown in Figure 4-7.

Figure 4-7 indicates: 6 AWG Wire (min.)*

It is somewhat vague whether the minimum refers to the “6 AWG Wire” statement, in which case something with greater current handling capacity than 6AWG wire would be allowed, or whether the minimum refers to the 6 AWG, in which case only larger wire would be allowed.

Personally, were I doing the inspection, and without further guidance, I would interpret this to mean the bus bar (assuming it has a greater current carrying capacity than a 6AWG wire) would be legal. Another inspector could rule differently, however, and I can’t say they’d be wrong. They could cite R48 All active circuits shall be wired with appropriately sized insulated wire: Personally, I read that as referring to branch circuits after the PD board, because the resulting table only goes up to 40A, however I totally see how someone else could read it differently, or use it as guidance that the GDC intended for wires to be the only way to conduct electricity.

There is also R50 to keep in mind: R50 All active circuit wiring with a constant polarity (i.e., except for outputs of relay modules, motor controllers, or sensor outputs) shall be color-coded as follows: so even if the bus bar were legal, it would have to be appropriately colour coded.

My suggestion would be to either ask the question on the Q&A forum, or prepare a length of 6AWG wire with appropriate terminal ends and bring it with you to the competition. That way, if the inspector does request a change, you undo two nuts and replace the bus bar with the wire.

Good question… but in lieu of a Q&A, I don’t think there is a definitive answer.


I disagree with Jason. I interpret “shall be” to mean “you must do it this way”, and with the other wiring rules using “minimum” to refer to a wire gauge (i.e., you can use larger wire, but you have to use wire), so no bus bar.

Given that two experienced FIRSTers with inspection experience disagree, I strongly recommend Q&A (nobody’s asked this one yet)–and then make sure to bring documentation with you, including the Q&A, at the event if it is ruled legal.

As The LRI for your team’s regional (North Star), I strongly, strongly encourage you to post this to the Q&A. With appropriate data sheets you could convince me it was safe… I would probably then feel the need to get a second opinion and have to place a call in to the GDC.

Please, safe us both a lot of time at the competition and ask on the Q&A before you implement it!