[paulengr]

Depends on use. If you work on old panels you will notice on some those suckers are so glued on a heat gun won’t do anything until they melt and you scrape the goo up. On others they just dangle off the wire like ornaments. I can say I’ve learned a few trick:

1. Wipe down the area first with denatured alcohol. Any oils or other residue will lead to failures.
2. Do not touch the sticky surface to ANYTHING. Peel and stick, period. If it is not a perfect attempt, toss it. Don’t skimp.
3. Maximum distance of about 4-6” between sticky backs. And bend the wire so they provide support and that’s it.
4. Stick them on way ahead of time. For some reason it seems like it takes a little time to really get stuck on good. I put them on before I run wire then stick the tie wraps in then run wire with the tie wraps in loose loops then come back with the tie wrap gun after the wire is landed in that order.
5. Use a tie wrap gun. It makes a difference.
6. Avoid using them!!

So wire duct looks great in the panel. The big advantage here is honestly your wiring can be total crap. Slap those lids on and all your sins disappear like magic. But there are two areas where this does not work. You don’t really want to run wire duct across a door panel because then you have screw heads (or worse) sticking out on the front. The other area is around bulky large components like contractors and drives. I tie wrap and use terminals as anchors where possible. So with a long row of contactor so will daisy chain the neutrals to the coils then run the longest run first tying it to the neutral with a tie wrap so it makes the wire hold a 90 degree bend. Then repeat for the next closest, and so on. This makes a nice tight and neat bundle. I use the same technique on push buttons. This leaves a couple tie wraps going from one row to another and a row leading up to the jumping off point to the back of the panel.

I don’t like the one hole sticky backs. The screw head always interferes with the tie wraps. If I have to use a screw I use the ones with two holes on either side and just pick one. Also a one hole “strap” anchor works way better than any sticky back once you see screwing things down.

My only downfall is anchoring the other end of the bundle going to the door. Drilling through and using a bolt and nut us a very strong anchor but if I could get rid of the bolt head i would. Maybe I’ll try a rivet nut next time.

 

[paulengr]

There’s rarely any need for sticky backs and tie wraps in a panel. If I’m the poor slob going into that panel after Leonardo DaVinci finished his masterpiece, I’m snipping tie wraps and tugging on wires just to re-arrange things. No thanks. Make it reasonably neat and put the cover on.

If I put the tie wraps on by hand, you can hand trace my wiring. If I use a tie wrap gun, you have no chance at all. It takes all of 5 minutes to put them all back and retie it. It takes less time to use the gun and it snips off the end so there is no sharp end. So if you attempt to trace my tie wraps, cut them. Just put them back for the next guy.

If done properly there should be an inch or two of slack. In a wire duct I just leave the inch or two in the duct. I cut it so it reaches the back/center of the trough. In tie wrapped wiring if you go into every terminal with a 90 degree turn and leave a gap to the turn or roll it down/back from the terminal you will leave plenty.

“Davinci” panels SHOULD have slack. Wire that is too tight can pull out, stress parts, and is a nightmare for parts replacement. If it’s that tight chances are others are too loose. It’s a sign of an amateur. NEC 300.14 requires a little slack for boxes. Panel wiring is different but the principles don’t change. Old panels used SIS or THHN. Most terminations had a 270 degree “roll”. With MTW or THHN “spaghetti” in a wire duct it should be run as if it’s centered in the duct to create 1-2” slack. Don’t be the jerk that zig-zags an extra foot of wire in every connection or has them so tight you can’t dress up the end after replacing a part. In tie wrapping it should still have an inch or two of slack, for the same reason.

CAN I make it “bus bar” tight? Yes. But chances are I will be working on my own stuff. I want to make it easy for me, too.

Ever seen a panel shop? Wire is “free” as in the cheapest part even at todays prices. There are scraps, usually under a few inches, everywhere. Same with a construction site. Except those guys that estimate 25 feet, pull 35 feet, and leave giant air core inductors piled up in the bottom of the panel. Code says 6-8 inches, not 6-8 feet. Do you really feel safe poking through that mess? I don’t either.

 

[paulengr]

I still occasionally use waxed string, I have a few rolls left, more than I have time left to use. But usually for telecom. Have you seen the NASA PDF (attached)?

I use Kevlar lacing cord. Because it’s nearly unbreakable and “free” at the motor shop. Mostly to bundle cables in peckerheads. You can buy it cheap at EIS Sales. This is what it is used to control:

You lace up the turns and the internal wiring at the ends then everything gets coated in epoxy or varnish when used in a motor (dip and bake or VPI and bake).

 

[paulengr]

Wiring duct makes panel building much easier. When using tyrap bases its a real pain to run all the wires perfectly to be tied down. In some instances bases work well for door operators. (push buttons and indicator lights).
Numbering being the most important thing. And building from a schematic.

Building from a wire list.

Field guys use schematics. Panel builders use wire lists. Many of them can’t read schematics.

It’s sort of like designers often just work off an IO list. The schematic is not used.

There are big advantages. UL requires you to lug the serial numbers of every part, even the wire. A wire list can have blanks for writing it down (tape worksheet in log book). If you have check off blanks you are less likely to miss a jumper. Panel building is very repetitive, both drawings and panels.

 

[paulengr]

So there's not code issues drilling screws/self-tappers into the side of panels?

Most panels are not Listed. So the distribution panel in your house is almost always not Listed. Only the bus bar frames and the breakers are a Listed assembly, not the box it goes in. Boxes must meet NEC OR be Listed.

 

[paulengr]

Those cannot be removed. There has to be a way to replace devices. I like them tough. Easy and no tapping.

We’ve debated this in house for a while. We sometimes deal with self contained panel mount style VFDs that weigh up to close to 500 pounds. A couple weeks ago we had a monster 700 HP, 407 pound VFD. It went into place nicely with a lift table. Then we get into supporting it.

Ultimate shear strength of a 1/4-28 Teks screw through 14 gauge sheet metal is 2350 pounds. Pullout is 1507 pounds. So with Teks they will pull out before they break iff..

Rivets can work but as stated it’s “permanent”. But there is an in between option, the rivet nut or rivnut. Mount like a normal rivet but remove the threaded insert then use like a threaded hole. Here are mechanical properties for Bollhiff brand:

https://www.rivetnutusa.com/wp-content/uploads/2019/01/Engineering-Data-Specifications-and-Mechanical-Properties-Information_Bollhoff-Rivnut-Rivet-Nut.pdf

Ultimate shear strength is 1100 pounds in steel. It is showing 1850 pounds shear strength. They have some special higher strength ones, too.

Finally for drilling and tapping bolts we have 1/4-20 is good for 1107 pounds shear in grade 5 or 1577 in grade 8.

Lesson learned: all 3 methods give fairly similar shear values for holding up a load, about 1100-1500 pounds shear strength, no safety margin included. So it comes down to which is safer, quicker, or cheaper.

 

[paulengr]

All other stuff doesn’t involve adhesive. Wire duct is the most obvious. But you can screw straps (or tie wraps) down or use rivets. It all works pretty similar. If I spent the time and money on a CNC where I could just feed it a list of holes and let it do the work I might feel differently.

Take a look at this video:

This video shows drilling about 50 holes for a typical control panel that uses 100% wire duct and DIN rails. No tie wraps anywhere. Think for a minute how much time is involved doing this by hand. Tie wraps greatly reduce the hole drilling time when there are just a few wires. Wire duct makes a lot more sense when you have lots of terminals close together.

The truth is I don’t do it that way. It’s faster to just use self tapping screws. They are just as strong as drilling and tapping and I can do it all in one, once and done. If you use rivet nuts you only drill and the rivet eliminates tapping. I guess the ultimate speed would be a stud gun and nuts but I don’t know where to find stud guns that do #8-10 studs.

 

[paulengr]

The coolest system I’ve seen for panel building is Satie System.

A Simple Idea: Simplify your Life | CMSMS Site, Manufacturer of custom frames for electrical enclosure

Here is the frame developed to optimize the assembly, wiring and troubleshooting of your automated systems. The Satie System makes the assembly and the...

www.satie-system.com

They bolt together. The wiring goes “behind”.