wire gauge

[Guest matthmelt]

There are a bunch of panels around here that use 12 awg, which is too difficult to work with. I noticed that the NFPA 79 says that 18 awg is the minimum for control circuits. From experience, is there any problem with wires pulling out, etc. using 16 awg (instead of 14 awg)? By the way, this is a great site/community and I appreciate all of the help. I just stumbled across this site a couple of weeks ago, but now it's always opened on my computer! Thanks, Matt

[ianbuckley]

You will need to know the current rating necessary for the circuits involved to know the minimum wire size required. With that caveat, 16 AWG is a fairly common standard for simple control signals inside a panel for the purposes of wire strength. 12AWG is a fairly common minimum size for motor wiring.

[Chris Elston]

Here is what we use. See attached. wire_info.pdf

[Sleepy Wombat]

So u guys all use 1.5mm for PLC IO wiring as well ? With a lot of PLC IO blocks gettting smaller and smaller 1.5mm can be a pain to work with i would go down to 1mm or 0.75mm on these anyway... American_Wire_Gauge__AWG__to_mm_Chart.PDF

[TimWilborne]

I looked through several companies wiring standards. None of them allow 18 awg wire. 16 awg minimum for control wiring 12 to 10 awg miniumum for motors

[TimWilborne]

Hey Sleepy, what is the difference between 18 and 18 (UL) in your chart?

[Sleepy Wombat]

Here's another one.. i chance to bet that when you guys use prefabed cables between a PLC io block and a terminal block say flex io the cable is a lot smaller the 16AWGWhat_is_the_different_between_AWG__SWG__and_BWG.pdf

[TimWilborne]

Well that just added two more methods. Wouldn't you hate to do it in lbs/mile

[gravitar]

This is a great reference. Practical guidelines, too! Allows DC conductors as small as 20 AWG individually, or 30 AWG as part of a cordset. Makes sense to me!

[Stupidav]

Personally I use 18 ga for most all of my internal wiring, and 16ga for external, unless device load dictates otherwise. I have seen equipment that utilized larger gage wire, 14ga or 12ga, that many of the wires have just fallen from the terminals. In equipment that I have seen with the smaller gage wiring, I haven't noticed same problem. Whether it has been a coinsidence or not is another story. With the smaller wire sizes, the panels generally look cleaner and installation generally goes alot faster because it is easier to work with.

[Clay B.]

I see alot of the 12 AWG in older equipment. New stuff seems to utilize the small wire more. I tend to stick with 18 awg for most control stuff. Motors I look at my drive/motor rating and size accordingly. For me it has been more the type of wire insulation instead of the size that dictates how easy it is to use. I have noticed that with newer terminal strips. larger varity of wireways, and most electronic items being Din rail mounted, that making a pannel look good is alot easier than in my fathers day. He has reminded me of that on several occasions.

[gravitar]

for sensors and low current outputs (lights, air valves, etc) 18 AWG is more than adequate. Remember that sensor cords are usually 22 AWG anyway! for everything else, let the load be your guide.

[Clay B.]

One other thing I noticed on European equipment that i have started doing is using ferrules. Like Gravitar mentioned, sensor wire tends to be 20 awg or smaller. Getting this to stay in place on a terminal block rate for 10 AWG can be a pain and can result in some weird happenings. Using ferrules makes for a better connection and the ferrules I use are nickle plated so less likely to corrode. I mention this due to seeing older equipment fail due to bad connections. Have gotten rid of alot of "grimlins" by just redoing the terminations with ferrules.

[charlesm]

Furrels are a must. They are well worth the extra time to install. We use 18awg for everything we can. I do like to go to 16 for anything that goes out of the panel.

[Crossbow]

18 for PLC I/O is more than adequate. I had a customer once used 22 for wiring DC transistor inputs and outputs. Since the inputs pull a couple mA, and the outputs rate out at typically .1 or .2A, there's no reason for large wires. And since the PLC relays outputs can't exceed 2A, 18 is more than enough. I've had customers want 12 for everything in the panel, and I kept an old PLC terminal block around. It was so hard to see what went where that they never asked again when I said 18 was enough.

[kcor]

Thanks Great Article