Oversizing conductors for voltage drop, terminal sizing

[cppoly]

If conductors are oversized for voltage drop and calcs come out good, what happens if they can't be terminated on lugs on a particular OCPD? For example 2 sets of 500 kcmil that need to go on a breaker that is listed for 2 sets of 350 kcmil.

 

[iwire]

First choice for me is to find out if the manafacturer has lugs available that will fit the 500s. Many breakers have diffrent lugs available.

If that is not possible just splice on some conductor that will fit the breaker using a suitable listed connector.

 

[jumper]

You could also use reducing pin terminals.

 

[cppoly]

Thanks

 

[cppoly]

First choice for me is to find out if the manafacturer has lugs available that will fit the 500s. Many breakers have diffrent lugs available.

If that is not possible just splice on some conductor that will fit the breaker using a suitable listed connector.

Does that mean the new larger lugs would replace the older smaller ones?

 

[kwired]

You may need to watch for wire bending space in this situation also. If the enclosure where you wish to terminate doesn't have the space needed you may need to reduce the conductor in a separate enclosure nearby.

 

[infinity]

You could try this:

 

[templdl]

First choice for me is to find out if the manafacturer has lugs available that will fit the 500s. Many breakers have diffrent lugs available.

If that is not possible just splice on some conductor that will fit the breaker using a suitable listed connector.

This is the result of either a failure of the person that is doing the take off to pay attention to the size of the cable an number per phase so that the issue can be addressed before and order is entered or the person that is ordering the OCPD without any consideration to what terminal are available. This is where the trouble starts.
They must read the catalog. It is extremely important to make it clear what the cables are that will be terminated even Cu or Al if applicable. The distributor and/or manufacture should address that issue right up front such that the correct or if they aren?t available you certainly will know what trouble you?re in up front instead of getting a surprise.
If you are dealing with a derating issue it is important to consider as to how your are going to terminate the custom conductor size.

 

[templdl]

You could try this:

This is the result of either a failure of the person that is doing the take off to pay attention to the size of the cable an number per phase so that the issue can be addressed before and order is entered or the person that is ordering the OCPD without any consideration to what terminal are available. This is where the trouble starts.
They must read the catalog. It is extremely important to make it clear what the cables are that will be terminated even Cu or Al if applicable. The distributor and/or manufacture should address that issue right up front such that the correct or if they aren?t available you certainly will know what trouble you?re in up front instead of getting a surprise.

 

[infinity]

This is the result of either a failure of the person that is doing the take off to pay attention to the size of the cable an number per phase so that the issue can be addressed before and order is entered or the person that is ordering the OCPD without any consideration to what terminal are available. This is where the trouble starts.
They must read the catalog. It is extremely important to make it clear what the cables are that will be terminated even Cu or Al if applicable. The distributor and/or manufacture should address that issue right up front such that the correct or if they aren?t available you certainly will know what trouble you?re in up front instead of getting a surprise.

Do you see a problem with the installation in the photo?

 

[iwire]

This is the result of either a failure of the person that is doing the take off to pay attention to the size of the cable an number per phase so that the issue can be addressed before and order is entered or the person that is ordering the OCPD without any consideration to what terminal are available. This is where the trouble starts.

True sometimes, other times terminations are not available to do the job without changing to different / larger equipment altogether needlessly adding cost to the job.

In Infinity's picture they would have had to buy a greatly oversized transfer switch just to accommodate the conductors chosen to address voltage drop.

I see nothing wrong with the solution shown.

 

[infinity]

True sometimes, other times terminations are not available to do the job without changing to different / larger equipment altogether needlessly adding cost to the job.

In Infinity's picture they would have had to buy a greatly oversized transfer switch just to accommodate the conductors chosen to address voltage drop.

I see nothing wrong with the solution shown.

Yes, the 200 amp ATS was nippled between the normal distribution board and the load panel. Those conductors were only about 8' long. The emergency feeder originate at the generator switchboard on the roof several hundred feet away. This seemed like a pretty good cost savings solution since a 200 amp switch was all that was needed.

 

[templdl]

Do you see a problem with the installation in the photo?

Not at all. The workmanship In the example looks superb. But it is a pain to have to adapt this method when backed to a corner though. I have always been of the belief that I want to know how much trouble I'm getting to before I do. To do the gig you may have to obtain a enclosure with enough room.
While assigned as an application engineer I found it to be not all that uncommon where the electrician was challenged with a mismatch of cable size and the terminations. It would be easy for my to say that there should have been better planning. b
BUT, the real issue at have is to help getting them out of a real jam. The workmanship In the example looks superb. Having 20/20 hind sight is of no help but only to point out the importance of better planning in the future.

 

[m sleem]

One concern i have. The third conductor out of the splice looks smaller than other. I know this part is acting as the breaker lugs which is not needed to be oversized. Do we have limitation for that length?

 

[kwired]

One concern i have. The third conductor out of the splice looks smaller than other. I know this part is acting as the breaker lugs which is not needed to be oversized. Do we have limitation for that length?

That is what this whole thread is about. Running oversized conductors for reasons such as voltage drop then finding one end or the other will not fit in the lugs it is supposed to land in.

Now if that were a breaker in the photo and this were a feeder tap, then the length would be limited by the feeder tap rules in 240.21, but if the smaller conductor is protected at or below its ampacity then we don't have a feeder tap and there is no length restriction.

 

[jdixon]

Well it seems to have 2 large conductors entering the reducer and 1 small conductor going to the OCPD

 

[jcbabb]

Well it seems to have 2 large conductors entering the reducer and 1 small conductor going to the OCPD

The smaller conductors are likely sized adequately for all the variables except for voltage drop. The larger paralleled conductors probably only take care of the voltage drop alone. The short length of smaller conductor is negligible when accounting for the voltage drop.

In my opinion, the length of the smaller conductor(s) would only be limited by the results of the voltage drop calculation. At the length shown, I would not even make the smaller conductors part of the equation.

 

[infinity]

Well it seems to have 2 large conductors entering the reducer and 1 small conductor going to the OCPD

This is a 200 amp ATS fed with #3/0 THHN (normal feed), #3/0 THHN (load) and parallel 350's (emergency). There is no OCPD in the photo.

 

[templdl]

True sometimes, other times terminations are not available to do the job without changing to different / larger equipment altogether needlessly adding cost to the job.

In Infinity's picture they would have had to buy a greatly oversized transfer switch just to accommodate the conductors chosen to address voltage drop.

I see nothing wrong with the solution shown.

Neither do I. I don't believe that I said there was. Did an over sized enclosure be required though?