mac adapters

[FVC electric]

Could someone please tell me the theory on why it would be wrong to give a wire a haircut so it could fit under a smaller lug. The wire I'm working with is a 600 kcmill and the lug is rated for 250 kcmill. I know it's the wrong thing to do but I'm having trouble trying to explain why its the wrong thing to do...I'm trying to convince them to order mac adapters and new lugs..

Thank You,
fvc

 

[chris kennedy]

Welcome to the Forum. You could start with 110.14 (A).

110.14 Electrical Connections.

(A) Terminals. Connection of conductors to terminal parts shall ensure a thoroughly good connection without damaging the conductors and shall be made by means of pressure connectors (including set-screw type), solder lugs, or splices to flexible leads. Connection by means of wire-binding screws or studs and nuts that have upturned lugs or the equivalent shall be permitted for 10 AWG or smaller conductors.

I would also consider 110.3(B) for the lug. No matter how much you trim, your still using a lug listed for 250 with a 600.

 

[Strife]

OY VEY
Where do I start?
Ok, would you put a #12 wire on a 60A breaker? You haircut a #6 wire to a #12 size you only got a #12 connection. As little length as that seem it'll overheat. As a matter of fact I don't think I ever seen wires melted inside a conduit because overheating (I've seen it because nicks in wires which lead to shorts), but I have seen (literally) thousands of melted lugs.
Now in a more mundane situation (customer?) this is how I would explain it:
Take, let's say a thousand pound rope. Then go anywhere on the rope and cut half the rope. Ask them if the rope will still withstand 1000 lbs?
I mean hey, go and cut in only 1/2" from the load, or the hoist. I mean, it's only half an inch, shouldn't matter? right?

Could someone please tell me the theory on why it would be wrong to give a wire a haircut so it could fit under a smaller lug. The wire I'm working with is a 600 kcmill and the lug is rated for 250 kcmill. I know it's the wrong thing to do but I'm having trouble trying to explain why its the wrong thing to do...I'm trying to convince them to order mac adapters and new lugs..

Thank You,
fvc

 

[pete m.]

Could someone please tell me the theory on why it would be wrong to give a wire a haircut so it could fit under a smaller lug. The wire I'm working with is a 600 kcmill and the lug is rated for 250 kcmill. I know it's the wrong thing to do but I'm having trouble trying to explain why its the wrong thing to do...I'm trying to convince them to order mac adapters and new lugs..

Thank You,
fvc

I think that the previous answers cover why it's not OK to give the wire a haircut. Another solution could be to splice a piece of 250 to the 600 (obviously using a proper splice method) so that the "haircut" is no longer needed. This of course is based on the assumption that you don't need the 600 due to ampacity concerns and that you have the space to make the splice.

Pete

 

[Strife]

I think that the previous answers cover why it's not OK to give the wire a haircut. Another solution could be to splice a piece of 250 to the 600 (obviously using a proper splice method) so that the "haircut" is no longer needed. This of course is based on the assumption that you don't need the 600 due to ampacity concerns and that you have the space to make the splice.

Pete

You'd still end up with a #12 wire on a 60A breaker.

 

[pete m.]

You'd still end up with a #12 wire on a 60A breaker.

No, you would end up with a 250kcmil conductor terminated on a lug that is rated for 250kcmil following what I said.

And yes, in some situations I could put a 12awg conductor on a 60 amp breaker (but only if the terminal is listed to accept a 12awg conductor....)

Pete

 

[FVC electric]

the load is only 200 amps... over kill I know but the conductors were existing. I was thinking of something called the skin effect. Is that were the electron flow on the outside of the wire. What I need to do is use a mac to a 500 then replace the 250 lug with a 500 lug.

 

[FVC electric]

hmm reply didn't come through

 

[jumper]

hmm reply didn't come through

?

 

[Strife]

Ok, if your OCPD is 200A I see no problem splicing the 600MC to a 250MCM, heck even a 3/0. I did it a few times, had to run 3/0 because voltage drop in a 100A breaker, I used polaris taps to go to #3. (or #4 on 30A breakers). I still wouldn't "haircut it" . How do you know how much ampacity is allowed through that "haircut" of yours? do you have a formula? Don't think in terms of "hey I cut half the strands, so it's good for half ampacity"
I don't care about the load, I care about the OCPD. Go back to the rope example. Take 1000 lbs rope, cut half the strands. Sure you can lift safely 250 lbs. But what will happened if the hoist is designed to lift 1000 lbs and you try to lift 1000lbs with it? Don't you think the hoist needs to be redesigned to fail lifting more than 250lbs?

the load is only 200 amps... over kill I know but the conductors were existing. I was thinking of something called the skin effect. Is that were the electron flow on the outside of the wire. What I need to do is use a mac to a 500 then replace the 250 lug with a 500 lug.

 

[bluesmoke...oops]

Ok, if your OCPD is 200A I see no problem splicing the 600MC to a 250MCM, heck even a 3/0. I did it a few times, had to run 3/0 because voltage drop in a 100A breaker, I used polaris taps to go to #3. (or #4 on 30A breakers). I still wouldn't "haircut it" . How do you know how much ampacity is allowed through that "haircut" of yours? do you have a formula? Don't think in terms of "hey I cut half the strands, so it's good for half ampacity"
I don't care about the load, I care about the OCPD. Go back to the rope example. Take 1000 lbs rope, cut half the strands. Sure you can lift safely 250 lbs. But what will happened if the hoist is designed to lift 1000 lbs and you try to lift 1000lbs with it? Don't you think the hoist needs to be redesigned to fail lifting more than 250lbs?

As is so often the stated case on here, if the guy coming to mess with it next looks and sees that it's been splices to a smaller size wire and lug and still insists on loading it for the full amperage the 600 can take, that person has no business doing the work to begin with.

And can't the "lift" be designed to fail at "250 lbs" by simply putting a breaker in? The op has already said they are gong to order new lugs and adapters.

 

[jim dungar]

I was thinking of something called the skin effect. Is that were the electron flow on the outside of the wire.

I wish people would stop teaching skin effect, or at least emphasis its proper use if they do.

Skin effect is where the current is not evenly distributed through the cross section of a conductor. There is more current on the outside of the conductor than in the middle, but there is still some current everywhere.

But, the biggest thing is: for the average electrician, skin effect is all but meaningless at 60Hz.

 

[LarryFine]

Take, let's say a thousand pound rope. Then go anywhere on the rope and cut half the rope. Ask them if the rope will still withstand 1000 lbs?

Sure, if you split it into two 500-lb loads. :grin: