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How much of a service loop is too much/unsupported wire?

Steve Crewdog

Well Known Member
Patron
Doing the final wiring on the panel, I've got an area under the radio that has a lot of wiring going into it, and for repair access I've made it into a removable subpanel. But in order to give enough slack to make the panel removable I've ended up with a considerable amount of extra slack/service loop.

I'm in the process of neatening it up, and I'm sure I'll have one more brace in there somehow, but wanted to throw it out for thoughts/criticism/suggestions, (maybe even an attaboy?), how much wire would you allow unsupported behind a panel like this? What do you do with the service loops?


Thanks for your time, see you at Sun n' Fun.
 

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There is some good info on this in AC 43.13 pages 11-52 to 11-55, which I'm using as a guide. For service loops it states that ties should be installed at 4 to 6-inch intervals.
 
At work, our standard is enough wire to make 3 connector repairs, then enough loop to remove the connector without straining the harness. Note: not all of the service loop needs to be right at the connector. Some installations are better having the loop spread out over the last foot or two of the harness, by being a bit more generous on spacing around structure, or slightly larger drip loops. We have installations where we have to remove several harness clamps to get enough loop to remove the item. Be neat and consistent as you go, it helps when you start having to troubleshoot a problem.
 
My assumption

My assumption; correct me if I'm wrong =

43.13 11-96a paraphrase

Wires (regardless of gage) should be supported no less than every 24 inches.

It would make sense to me that it is referencing wire weight/unit-length relative to its associated strength. There is no mention of orientation. If my assumption is true, a service loop can't be any larger than ~7.5"D unless supported at least twice in the loop.

Yes, I'm aware it is an "Advisory" circular.
 

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If it is a relatively large bundle, a service loop kind of self-supports if the lacing or tie wraps are relatively tight. By being bundled, all the wires work as one large wire and avoids flexing and movement, due to the inherent rigidity of the bundle.
 
Thanks gang. I posted a little early last night, I was tired and a little overwhelmed at the spaghetti monster of wires and decided to walk away, which is always a good thing. Fresh eyes and fresh head after a good night's sleep, back at it today. I appreciate the guidance.
 
Steve: There are a large number of photos on the net that show good installations. Before you get too frustrated, pull a few up and see how they did things.
 
If it is a relatively large bundle, a service loop kind of self-supports if the lacing or tie wraps are relatively tight. By being bundled, all the wires work as one large wire and avoids flexing and movement, due to the inherent rigidity of the bundle.

It does to a point, which is what I'm going to look at today. There are 25 wires going into that subpanel, 8 into a mini-molex connector all bundled together (eFlap, the 4 vertical squares), most of the wires go off to the right but a handful go left, so I have to give slack on both sides for everything to be removed, but not too much. I thought I had it all figured out before I took it apart to apply the veneer, I'm sure I put something back together in sequence wrong and need to remember. Thank goodness for camera phones, before I take something apart I've learned to take a bunch of pics. (and STILL miss the ONE ANGLE I NEED!!! :D )


Steve: There are a large number of photos on the net that show good installations. Before you get too frustrated, pull a few up and see how they did things.

Yessir, that's on my list of things to do when I get to the hangar today. Thanks for the reminder.



later, from the hangar....

Sometimes, you just need to step away from one problem and go work on another one for the solution to the first problem to come to you. Then you have to decide: Stop what you're doing and go back to the first problem, or finish what you're doing and risk losing the mental solution to the first problem. (Or am I the only one that thinks this way?)

What I realized was that what I thought was service loops was really just a LOT of extra wire (I cut them long because it's easier to make them shorter, but hard to...), and all I really need is enough to be able to pull the sub-panel out and disconnect the light/switch/CB, so when I get home next week (and after the honeydos are done) I'll be out again with a pair of wire snips and my soldering iron.



I love a good day in the shop. Thanks, everyone.
 

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