Plenum cable: Is it legal?

Trying to find wires for our 2018 bot and wondering if will be acceptable in competition.
Thank you.

Yeah I think that is fine, but check the rules. From what I can see, it is just wire within an additional insulated housing. Looks like a very small gauge though.

I think it should be OK anywhere that 18 AWG wire is allowed (20A breakers, roboRIO power, VRM/PCM power etc). But please remember that the rules could be different in 2018, so no guarantees.

Whether it’s legal will depend on what you are using it for. You cannot use 18 gauge wire on a 40 amp circuit, for example. Those same people do sell a 12/2 cable, which you could use. But, most people here would recommend using 10 AWG for those circuits. Also, you probably want zip cord and not something with an extra sheath that you have to deal with.

See table 8-4 in last year’s manual for the requirements. It’s conceivable that those would change this year, but that seems unlikely.

Yep, definitely watch the wire gauge. For 40A breakers, you’ll want this one.

There are two concerns the inspector will verify, so be sure to have the data sheet ready:

  • The wires must be the right gauge. No one wants a robot fire. 2017 rules stipulate 31-40A breakers must have 12AWG wire.
  • The wires are all-copper, not copper-coated tin.

I’m not saying you WILL run into problems with R59, but it’s something you should pay attention to.

By my reading, that should be okay because each wire is colored correctly. But I could see an inspector reading that differently and saying “the negative wire is also white on the outside, so it’s not legal”

I don’t see a problem with it as far as rules go, I guess I’m just wondering what the advantage to using this kind of cable would be over something like the far more common bonded wire that a lot of teams use. It seems like you’re just adding weight with the extra jacket.

Some jacketed wire does not have the wire sizes printed on the outside. Most un-jacketed wires have the wire sizes printed along the length. A really picky RI might try to make you prove that the wire sizes are what they are, causing delays in the inspection process.

The extra bulk and stiffness of the jacket may make it more difficult to run the wires if your layout is cramped.

Jackets on wires have their most value in avoiding abrasion when long runs of the wire are pulled along cable trays or through conduits. They are hard to justify on FRC robots.

Thank you all so much for your quick and very helpful replies.
We are trying to find the best wires to use. we thought that red/black zip-wire would help keep things neater, so we were wondering your thoughts on zip-wire in general and is there a better price anywhere else? (the extra weight from the outer jacket was a concern here also). Thank you.

Also, note that Plenum cable is generally more expensive than non-Plenum. Non-plenum cable gives off more smoke and toxic gasses when it burns than does plenum cable. That’s an important consideration if you’re wiring a building and have thousands of feet of the stuff going all over the place, but not so much on a robot.

Here’s what we’re planning on this year:

This is far-and-away my favorite solution for FRC wiring.

Plenum cable exists to provide a fire rating to electrical cabling above suspended dropped ceilings.

It has a minimum bend radius of around 2 inches. You need to use a special (~$30) tool to strip the jacket off consistently. Using a knife to strip the jacket is almost guaranteed to nick some of conductor wires on a regular basis.

The use of zip ties (with anchors) and perhaps some clear heat-shrink-tubing would seem to be a far simpler solution to organizing your wiring as needed.

We have used other covered wire extensively in the past. As long as other robot rules are followed (wire gauge, individual wire colors, ETC) you should not have a problem. This is something I would politely refer to the LRI if an inspector has a concern with it. Of course if your inspector is the LRI, then you are rewiring your robot. :eek:

Thank you all so much for the great suggestions, recommendations and warnings. After comparing the costs of 100 feet, 12 ga, stranded copper wire with red and black pvc-jacket, we decided to purchase two spools: one (less expensive) with the white outer sheath and a zip cord, for our practice wiring from Monoprice
And one zip-line spool with which we will do our final wiring from Newark (formerly Stellar):
We compared the 100-foot equivalent price (shipping to south-central Michigan) from 8 companies and found these to be for us the least up-front cost.
If you have any further suggestions or warnings, please let us know, otherwise thank you so much for this help. :slight_smile:

Here’s more information than you probably wanted about what plenum and riser cable ratings (like CL2, CL3 and CM) mean. Yours was rated CMP, which is a highly flame-resistant cable.

Note that plenum or riser doesn’t inherently say anything about the flexibility or gauge of the cable. It’s just that a lot of the cables that happen to be rated for plenum use are for mains electrical wiring, which tends to be big and stiff. But you can get rather flexible plenum-rated network cable too, for example.

First point… definitely.

Second point… that’s not something I’ve ever checked for as an inspector. Could you please reference the relevant rule?



It was a rule at one time, if I’m not mistaken–or else there was a ban on aluminum wire. One of the two.

The 2017 rule is “appropriately sized insulated wire” (R57). 2018, who knows?

We use the monoprice 12awg and 18awg wire for most of our wiring. It’s cheap, works well, and it’s already covered in white so we don’t have to (no one has to, we just like to) put mesh sleeves over it if we don’t want to (we still do sometimes).

The reference to copper covered tin is really the other way around, as in ‘tinned copper’. Generally the only copper plated wire or copper cladding is for steel core wires. These have specific uses and are generally used where the wire must support it’s own weight without sag.
Plenum rated cables should meet electrical rules provided all other electrical rules are in compliance. However, plenum and other jacketed cables weigh almost twice what unjacketed cables will for the same AWG sizes. A strip string will add even more weight. When you are looking to lose weight, jacketed cables are the first thing to replace for weight reduction.
Plenum rated cables are designed to reduce harmful gasses from being emitted by the cable during a fire. Many building designs use the space above a suspended ceiling as the return plenum for the HVAC system.
Where I work there is so much video coax, camera cable and audio wiring there is no way to make all of it plenum rated. I have told all my coworkers to just get out as fast they can if there is ever a fire. There is nothing they can do to save anything worth the alternative to staying inside.

I feel like this is just good advice in general - regardless of plenum grade cabling.