storeytime
Member
- Location
- Texas
Does NEC require anti-seize compound to be put on the threads of breaker lugs in an outdoor switch gear?
Anti-seize compound on outdoor breaker lugs
- Thread starter storeytime
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
As a general rule no unless it's part of the manufacturer's instructions that are part of the equipment listing.
- Location
- Illinois
- Occupation
- retired electrician
If you do that and then torque to the specification, you will likely break the breaker.
storeytime
Member
- Location
- Texas
Thank you. That was my thought exactly. We just finished terminating and torqueing 30 switch gear, each with twelve, 3P breakers. We didn't use anti-seize. We're working under another EC. who thought it was required.
Last edited:
ptonsparky
Tom
- Occupation
- EC - retired
We used to use corrosion inhibitor on the Al wires, but never anti-seize on the threads
storeytime
Member
- Location
- Texas
We do on AL also but this is all copper wire.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Why do you say that? It will lube the threads allowing you to get there easier but the torque is the torque. Unless you overshoot because it turns so easy. ETA: Or are you saying that the torque spec accounts for dry threads?
To the OP's question, no. It was never required or even recommended to be applied to screw threads, only the AL conductors.
Only exception might be the threads on AL rigid conduit.
-Hal
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Torque specs for fasteners (nuts on bolts, lug nuts on car wheels, etc.) typically are set to produce the desired linear force on the bearing surfaces assuming the friction of dry threads is contributing to the measured torque.
Torque on pipe joints, OTOH, is often not specified, but the "feel" assumes lubricated threads as well as the increasing thread force from tapered threads.
- Location
- Illinois
- Occupation
- retired electrician
Yes I am saying that the torque spec is based on dry threads, and putting lubrication on the threads will result in greater contact pressure and may damage the lug and/or conductor.
mikeames
Senior Member
- Location
- Germantown MD
- Occupation
- Teacher - Master Electrician - 2017 NEC
Torque is torque but the pressure put on the lug and the conductor will be greater if there is less friction in the threads. This is also true when engine building. They will specify torque with and without additives.
On engine building you have a fixed threaded port that the bolts are threading into, unlike a breaker or meter lugs which are in themselves a bolted connection to the device.
I've yet to torque a lug on a breaker, Panel or meterbase with a torque wrench to spec without feeling like It's fixing to break completely off even with the aid of a wrench to keep the lugs from twisting.
JAP>
I've yet to torque a lug on a breaker, Panel or meterbase with a torque wrench to spec without feeling like It's fixing to break completely off even with the aid of a wrench to keep the lugs from twisting.
JAP>
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Torque is really about fastener stretching.
A lug seizing in the dry threads will most likely do more damage whether it happens when you're tightening or loosening.
Lugs if aluminum tends to gall the threads. It's just in it's nature.
The whole point is to try and keep that from happening.
I too am in the camp that applies anti-ox to the threads for lubrication whether required or not.
JAP>
Lugs if aluminum tends to gall the threads. It's just in it's nature.
The whole point is to try and keep that from happening.
I too am in the camp that applies anti-ox to the threads for lubrication whether required or not.
JAP>
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Visualize driving a wedge into a tapered slot between two pieces of metal while you measure the clamping force required to hold the two pieces together.
If the wedge is ideally lubricated the relation between the driving force on the wedge and the spreading force on the pieces depends only on the wedge angle.
If the wedge and the two pieces of metal have sandpaper glued to their surfaces, the spreading force for any given force applied to the wedge will be far lower.
For this purpose a screw thread is simply a long wedge wrapped in a spiral.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Yep, a modified inclined plane, one of the seven basic machines.
- Location
- Illinois
- Occupation
- retired electrician
Where you are fastening things together that is true, but I think for wire connections in a lug it is about "compressing" the conductor.
It is, but depending on the lug design, either the screw or the lug box is in tension. That’s where the stretch comes into play.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
But the relationship between the elongation and the torque required is still strongly dependent on the thread friction.
Your point is well taken if instead of measuring torque you specify "finger tight plus N turns". That is independent of thread friction.
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