Transformer secondary taps

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jim dungar

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Hmmm, secondary conductors versus tap conductors.

240.4(E) TAP CONDUCTORS
240.4(F) TRANSFORMER SECONDARY CONDUCTORS.

If transformer secondary conductors are actually tap conductors why do we need 240.4(E) and (F)?

Should most transformer secondary conductors be treated more like service conductors (which also do not have overcurrent protection) rather than tap conductors (which have oversized overcurrent protection)???
 

sandsnow

Senior Member
don_resqcapt19 said:
The secondary conductors of all transformers except two wire to two wire and three wire to three wire delta/delta transformers are taps and in some cases even the secondary conductors of these types are taps.

I think we think of them as taps because that is what the Code used to say.

The old 10 foot tap rule exception:
Feeder taps not over 10 feet long. For conductors tapped to a feeder or transformer secondary where all the following conditions are met:

The conductors off the secondary side of a xfmr do not meet the definition of tap conductors.
 

sandsnow

Senior Member
jim dungar said:
Hmmm, secondary conductors versus tap conductors.

240.4(E) TAP CONDUCTORS
240.4(F) TRANSFORMER SECONDARY CONDUCTORS.

If transformer secondary conductors are actually tap conductors why do we need 240.4(E) and (F)?

Should most transformer secondary conductors be treated more like service conductors (which also do not have overcurrent protection) rather than tap conductors (which have oversized overcurrent protection)???

I think you hit the nail on the head. Electrically it is the same set up as a utility service. No protection on the conductors.
 

Davebones

Senior Member
Do I understand this right some of us think we need protection after the transformer ( Fuses or Breaker) before I run into wireway and then into 2 fusible disconnects,and others say I can come from the transformer into the wireway and tap from there to 2 fusible disconnects!!!!!!!!
 

don_resqcapt19

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retired electrician
It is still my opinion that the transformer secondary conductors meet the defintion of a tap and are tap conductors. If you want to call them transformer secondary conductors, fine, but that does not change my position on this installation. You cannot extend conductors from the transformer secondary terminals and make connections to them to feed multiple OCPDs. This is a violation of the very first part of 240.21. Note that this section does not use the word "tap".
240.21 ... No conductor supplied under the provisions of 240.21(A) through (G) shall supply another conductor under those provisions, except through an overcurrent protective device meeting the requirements of 240.4.
The transformer secondary conductor was installed using the provision in 240.21(C). Any connection to those conductors with out overcurrent protection would have to use the provisions of 240.21(B) creating the "tapping the tap" violation.
 

don_resqcapt19

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Davebones said:
Do I understand this right some of us think we need protection after the transformer ( Fuses or Breaker) before I run into wireway and then into 2 fusible disconnects,and others say I can come from the transformer into the wireway and tap from there to 2 fusible disconnects!!!!!!!!
Dave,
I think the code is very clear here...you can run multiple sets of conductors from the transformer secondary terminals to multiple OCPDs, but you cannot run a single set from the transformer terminals and "tap" or "tee" it to multiple OCPDs.
 
don_resqcapt19 said:
Dave,
I think the code is very clear here...you can run multiple sets of conductors from the transformer secondary terminals to multiple OCPDs, but you cannot run a single set from the transformer terminals and "tap" or "tee" it to multiple OCPDs.


I agree with this statement, the change of wording in the 2008 NEC makes this very clear.


From our earlier conversation, I think you and I were misunderstanding each other about the term tap conductors.
 

Davebones

Senior Member
Any new setups in plant will run from transformer secondary to fusible switch (line side) , then to wireway (off of load side)then tap off in wireway to 2 fusible disconnects.As it is now there are 5 transformer setups here where they went transformer to wireway and tapped off to multiple disconnects (Guess thats the way done back then 1981) .To all who wrote in thanks for the help.
 

sandsnow

Senior Member
don_resqcapt19 said:
It is still my opinion that the transformer secondary conductors meet the defintion of a tap and are tap conductors. If you want to call them transformer secondary conductors, fine, but that does not change my position on this installation. You cannot extend conductors from the transformer secondary terminals and make connections to them to feed multiple OCPDs. This is a violation of the very first part of 240.21. Note that this section does not use the word "tap".

The transformer secondary conductor was installed using the provision in 240.21(C). Any connection to those conductors with out overcurrent protection would have to use the provisions of 240.21(B) creating the "tapping the tap" violation.


The 2008 NEC 240.21(C)(3)(2) allows you to supply multiple OCPD's from a set of secondary conductors. While it doesn't say it directly, it appears implied.

How can you do this without tapping? This is what the OP was talking about.

This appears to be a contradiction in the Code.
 

benaround

Senior Member
Location
Arizona
If you have a NECHandbook look at Exhibit 240.9

It shows the primary plus the secondary in total as the 25ft. TAP conductors

Seems like a secondary conductor and a tap conductor can be one in the

same at times.
 

sandsnow

Senior Member
benaround said:
If you have a NECHandbook look at Exhibit 240.9

It shows the primary plus the secondary in total as the 25ft. TAP conductors

Seems like a secondary conductor and a tap conductor can be one in the

same at times.

To me that looks like the primary conductors are the tap.
 

sandsnow

Senior Member
don_resqcapt19 said:
Larry,
Yes that does appear to permit tapping a tap.

I couldn't for the life of me figure out this thing. Then the my fellow electrical inspector here pointed out that this subsection is intended for use where the sceondary conductors supply a panelboard.
 

charlie

Senior Member
Location
Indianapolis
This is an interesting thread and the "tap" question is still confusing. Panel 10 would welcome proposals to clear up the confusion. As is obvious, you guys do understand what a tap is and is not but the tap rules are not so clear to others. I know what the panel's discussion on the subject has been and we have never considered increasing the wire size where a "tap" is made when tapping a tap. Is this a problem (I don't believe it is)? Should it be fixed (probably yes)?

You now have the basis for a couple of proposals; fix the definition of tap and make the text more clear to stop all of the confusion. Keep in mind that proposals have to be written in legalese so they will stand up in court. Also, there is a portion of the forum that is dedicated to helping you submit good proposals. :)
 

don_resqcapt19

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Illinois
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retired electrician
sandsnow said:
I couldn't for the life of me figure out this thing. Then the my fellow electrical inspector here pointed out that this subsection is intended for use where the sceondary conductors supply a panelboard.
I thought that at first, but what about 240.21(C)(3)(3)? While the term "grouped" would include a panelboard it also includes individual disconnects.
 

sandsnow

Senior Member
don_resqcapt19 said:
I thought that at first, but what about 240.21(C)(3)(3)? While the term "grouped" would include a panelboard it also includes individual disconnects.

I agree. So a good palce for clarification during the next Code cycle.
 

RUWired

Senior Member
Location
Pa.
Don, i agree with everything you have said about tap conductors and 240.21 where it says " Conductors supplied under the provisions of 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4.". The only point i have is, if it was important not to splice a conductor, then i think it would have been worded as such in 240.21(B)4(6).

"(6) The tap conductors are continuous from end-to-end and contain no splices. "

Rick
 

don_resqcapt19

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Location
Illinois
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retired electrician
Rick,
I am not saying that it is important to not have splices or that the splices cause any type of problem. I am just saying that you you make a splice or other connection to a conductor that is a "tap" conductor, that connection creates a code violation. Would any inspector "red tag" it? Probably not...unless you had given him a hard time in the past:D
 

charlie

Senior Member
Location
Indianapolis
don_resqcapt19 said:
. . . you you make a splice or other connection to a conductor that is a "tap" conductor, that connection creates a code violation. . .
Don, I can't speak for Panel 10 or give you an official interpretation; however, I think you are incorrect unless the splice or connection is to a smaller conductor than the original tap conductor. :)
 

finhead

Senior Member
I hate to beat a dead horse before the weekend, but it just occured to me that if extending a conductor connected to the secondary of a transformer with a butt splice constitutes tapping a tap, then the conductor connected to the transformer secondary is also tapping a tap. Is it not, itself, connected to a tap conductor (the secondary bus of the transformer)?
 
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