Wire Slack for Interior to Interior

[theColonel26]

My thoughts on slack for a wire that goes from one point in a panel to another point in the same panel is that there should be enough slack for the wire to lay in the bottom of the cable tray, even if it can't, because of other wires. So that is usually like 2-4in (50-75mm) of slack on each end, so like 4-8 total.

I have seen others that leave between 1 to 3ft of slack.


For the purposes of this thread we are not talking about cables that come in or go out of the box. That is a difference subject as they are not as easy to replace if you need to relocate something.

 

[OkiePC]

Enough so that you can scoot things to insert a new module, or a few more terminal blocks. Not so much you have to loop it multiple times. If there is little space left in the wire duct, I won't try to leave so much that I have to loop it. If there is lots of space, I will go past the exit point a couple of inches and loop it back.

 

[mylespetro]

Depends on the layout of the panel, but I usually like to see a small service loop hidden inside the wire trough (if there is any) so that if things have to be moved around a little bit (like OkiePC said) there's enough slack so that you can do that easily and reroute it through different openings in the wire trough if necessary.

 

[Aabeck]

I had the "opportunity" to work on a panel built by a customer's ex-employee that I would have kicked if he was still there.

Siemens S7-300 with 2 racks and not 1/2" of slack on any wire in the cabinet.

Pulling a connector off a card was impossible, safety relays and signal conditioners could not be removed from the DIN rail to get to the connections, and more.

I guess the guy saved about $3.50 in purchasing wire to the pain of anyone that has to work on it now. Even the maintenance supervisor there says he hates working on that panel.

I make sure there is enough slack to pull cards & DIN components.

 

[Rson]

Depends upon the type of wire.

For 480V connections from a disconnect to a PDB OR from a PDB to a circuit breaker/fuse/etc, I require a loop for two reasons:
1 - you can move things if needed (even though you don't typically move these components)
2 - I can put a clamp meter on the coil to measure amps

Our panels typically wire everything to terminal blocks. I require enough wire to be able to terminate from one terminal at least half-way up/down the terminal block (within reason). This means there usually isn't much slack on the PLC side of things, but plenty on the terminal block side.

 

[mylespetro]

2 - I can put a clamp meter on the coil to measure amps

This is a good point, if you're in a crowded panel it's great to be able to get your finger behind a wire to put a clamp meter on it, whether it's a standard clamp meter or a small 4-20mA clamp.

 

[Friedrich]

I also think there should be enough slack to move things a bit. Makes life so much easier, both when fault tracing and rebuilding/changing something.

Also had the discomfort to work on panels with no slack, and it's not fun to say the least.
Only thing worse is really tight cabinets or junction boxes.. The kind where you can barely fit the wire between the wall and terminal/unit.

 

[Timbert]

Enough so that you can scoot things to insert a new module, or a few more terminal blocks. Not so much you have to loop it multiple times. If there is little space left in the wire duct, I won't try to leave so much that I have to loop it. If there is lots of space, I will go past the exit point a couple of inches and loop it back.

This is my feeling too. Enough that it sits in the tray nicely, doesn't have any loops, enough extra so that I could re-terminate it or move the device slightly without issue.

 

[James Mcquade]

Leave enough room so you can trace wires, add terminal blocks, I/o card. NO wire ties in the wire trough / Panduit!!! I had to cut 53 wireties off 12 wires just to trace 1 loose connection. it took 90 minutes !
james

 

[OkiePC]

... No wire ties in the wire trough / panduit!!! I had to cut 53 wireties off 12 wires just to trace 1 loose connection. It took 90 minutes !
James

+1

 

[JesperMP]

Lots of extra wire - 15 cm (6 inches). Enough so that the wire can reach any terminal that you could potentially want it to.
And large wire ducts.