Over rated wiring?

[jstolaruk]

480VAC 3 phase motors (most < 3 hp) - 10 or 12 AWG Black (some of our vendor installs use Brn/Org/Yel of the same AWG rating)
120VAC controls - 14 AWG red
120VAC nuetrals - 14 AWG white
24VDC controls - 16 AWG blue
Grounding - Equivelant AWG of above mentioned with Green wire

This is pretty common on our customer's specifications though the its 16awg for 120vac controls and neutrals (rare for control wiring, mostly retool of older panels).

 

[Eric Nelson]

On an unrelated note--What ever happened to Allen Nelson? Anyone know? His last activity was in February I think. I hope all is well.

I had the same concern a few months back (being a Nelson and all)...

Phil was able to touch base with him. Seems he's just been busy. I still have an unread PM to him from May 28^th, so I guess he's been REALLY busy...

Imagine how many "New Posts Since Your Last Visit" he'll have. Can the forum display a number that large?...



-Eric

 

[Rube]

Thanks Eric--good to know.

BTW sorry for hijacking your thread Monkeyhead! Good luck with your electricians.

 

[monkeyhead]

Alrighty... What you've all said makes sense. Definately seems like it's situation dependent though. For hardpiped control wiring that won't be moving and isn't that far from the panel, then the extra size still seems like a waste to me. But I've also had to re-run motor wiring when jumping up in HP so that nailed the point home to me.

And I agree that anything smaller than 3/4" conduit is pointless. 1/2" sealtight branches here and ther ain't bad, but I cringe whenever I realize i'm gonna have to to try to stuff some extra conductors in a 1/2" pipe run. Seems like once it's got a few wires in there I can barely get my fish tape stuffed through.

 

[Jimmie_Ohio]

Upon first glance of the previous replies, I didn't see the topic I am about to mention.

I've been in "industrial control panels" since the 70's. I had a customer with a wire sizing specification similar to the one posted in this thread. Here's what my customer said way back then...

"We size our wire higher, because our electricians nick a couple of strands on every wire. When you take into account going terminal box to terminal box over several hundred feet, in some cases, we are lucky to get the equivalent of 16AWG after starting with 14AWG."

As a panel guy, I always made sure that my people used good strippers. If you want to save money and lower your wire sizes, be sure that you specify a good termination technique. For example use of wire lugs or ferules and terminals that have easy to manage wire entry. Also, make sure that your QC department and electrical supervisors monitor the quality of wire terminations.

Just my suggestion...

 

[Rube]

If you (they) are sizing the control wires close enough that they have to worry about a couple of strands of copper--that's too close to needing the next size wire anyway. But I do agree with good stripping/terminating techniques.

 

[brucechase]

Both sides of the coin

Since I consider myself a "sparkie" and a controls guy (along with the dreaded engineer designation), I would like to give my opinion on this. At this plant, I have standardized on:

#12 AWG MTW 600V Black for motors
#14 AWG MTW 600V White and Red for AC inputs/outputs
#16 AWG MTW 600V Blue for 24 VDC inputs/outputs
Ground in accordance with the running conductors
3/4" rigid is the minimum conduit, even though most of what I run is in 4X4 laying wireway
Ferrules in all panel terminations
Quick release TB (instead of screw terminals or the IDC)
Field splices in a FS box with Buchanan's (bullets)
QD cable on everything (if possible)

As for the wiring, in addition to the many good points from both sides, we do most (98%) of our own wiring, and standardization is wonderful. I keep one size of wire for each color and one size of terminations (bullets) and TB for each color. This makes for a neater and faster installation. It also prevents some mishaps that I've seen in other places such as having a motor with 2 #12 and 1 #14. The cost difference on wire isn't that great, last time I bought wire (about 3 months ago) it was:
$60/1000' #12
$40/1000' #14
$35/1000' #16
And since I installed 87,000 feet, changing the motors leads (which were 32 motors) MIGHT have saved $1700 but would have significantly increased the risk of having the 1 or 2 different size motor pulls being wrong.

 

[jstolaruk]

"ferules"

I get more complaints from our electricians on these, but of course because it takes extra time to crimp them on.

Privately, I question the need for them.

 

[brucechase]

"ferules"

I get more complaints from our electricians on these, but of course because it takes extra time to crimp them on.

Privately, I question the need for them.

Not to sound like I'm starting an argument, but if you ever had to troubleshoot a problem of a device doing something screwy and found that when the wire was landed on the screw terminal block the person got lazy and crammed it in there and now a few strands are touching the adjacent point, you wouldn't question the need for the ferrule. Especially on some of this new IEC stuff, the wiring terminal points leave no room for mistakes.

 

[Rube]

That's as bad as getting a new piece of equipment and finding one of the wires landed to a motor contactor wasn't ever stripped, single-phasing the motor from the get-go!

 

[jstolaruk]

Not to sound like I'm starting an argument, but if you ever had to troubleshoot a problem of a device doing something screwy and found that when the wire was landed on the screw terminal block the person got lazy and crammed it in there and now a few strands are touching the adjacent point, you wouldn't question the need for the ferrule. Especially on some of this new IEC stuff, the wiring terminal points leave no room for mistakes.

Yes, you're right about that, and I have run into that but its been so rare thats why I question the need for them. On the hand I've seen the ferrules miscrimped with strands hanging out of them too. So its 6 of one, half dozen of the other.

 

[rta53]

You have to consider more than the size when determining what is to be used. In general the wire used will be capable of the maximum current possible on that circuit....ie if the circuit is fused at 40 amps then the wire must be able to carry 40 amps even if the only item used in that circuit is a 1HP motor that draws 5 amps or less.

A 3PH 480 motor would carry maybe 5 amps but start current could be 30-40 amps or more, the use of at least 12 gauge is appropriate with motor loads. The guideline is 125% of full rated load but there are more issues to consider in a manufacturing plant.

Ron,

Do you size wire for a motor based on starting current? Where does the NEC require this? I have always used the 125% rule for wire size, which is what you are saying in your second paragraph.

 

[silva.foxx]

Not to sound like I'm starting an argument, but if you ever had to troubleshoot a problem of a device doing something screwy and found that when the wire was landed on the screw terminal block the person got lazy and crammed it in there and now a few strands are touching the adjacent point, you wouldn't question the need for the ferrule. Especially on some of this new IEC stuff, the wiring terminal points leave no room for mistakes.

"Whiskers" make beautiful circuits to where they shouldn't branch to. The best time to create "whiskers" is in cramped rat's nests usually found in old, low mounted panels in wet environments with mixed voltages and undersized cabling in dark areas. I love to troubleshoot them, especially at 3am with a banging headache and the sandman doing his worst. That's reality!

 

[Bruce99]

rate vs size

Wire size is determined by load. Fuses are to protect the circuit and overloads the motors. The code sets out minimum standards for all electrical installations. Many companies limit their stock of wire and cable, but using a #10 for a 480v 1 HP 3 Phase motor? The code also has rules regarding the max allowable JB fill. Many smaller motors have JBs that are too small for this size wire. Remember, the engineer designed the motor and JB with cost in mind. I have used some colourful language as I had to get a larger JB from a different motor and modify it to fit, in some cases adding hours to the project. Ive seen 4X4 boxes nippled into the motor, 8X10 Hammond boxes, and even pull boxes modified to fit. This looks like ****. If you really have to "up" size, limit it to one wire size OK? Your Electricians will thank you, I will thank you...

 

[Lancie1]

Rube,

And Lancie1 said using oversize wire may keep electricians (is that better, ha-ha) from having to stock different wire sizes. I argue that my contractors should install the wire I need them to install and as long as I legal and safe, what do I care if they have to get rolls of 14 wire when they pick up their rolls of 12 wire?

It all depends on the situation at the plant. I was thinking of a place where I once worked. We had our own electricians, and our own warehouse, and were required to keep spare parts for EVERYTHING in the plant that might fail. Keeping a stock of wire for every type used took a lot of space. If you haven't thought about it, start listing all the different types of electrical cable in a typical plant. We started trying to standardize and minimize the number of different types to keep from running out of room in the warehouse.

I know most of this is personal taste, and CFS, but I'm paying the bill. I always take the advice mentioned by Ron and Lancie1 (is there a Lancie2?) before I spec the project to the electricians--look down the road and see what might happen. If needed, go bigger. If not, save your pennies, uh, copper

Yes, apparently there is. He sent me an E-mail once. That was several years ago when I had an account at AOL.com. If you remember, AOL first assigned user names by taking your first name and adding a number to it. I happened to get the Lancie1, but another Lancie offered me $50 if I would give up the "1" and let him have it! He was a twenty-something, so I told him that I was here when he was only a thought in his Daddy's mind.