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#83387 - 01/29/03 09:43 PM Branch Circuit or Tap?  
Michael Luersen  Offline
Junior Member
Joined: Jan 2003
Posts: 5
Bedford, Texas, USA
[Linked Image] This is basically a tap/branch circuit issue.

First let me describe the circuit design.
We are feeding 6 – 400w, 480vac light fixtures spaced over a 500 span. The light fixtures are installed outdoors recessed in metal panels attached between support beams of a bridge.
We have a 480 vac, 20 amp 2 pole breaker feeding two #10 awg conductors, one #12 bare copper ground conductor in a ¾” conduit. (#10 was used for voltage drop)
The ¾” conduit runs the entire length and has a type T conduit body installed in line with the conduit near each light fixture.
Attached to the conduit body is a section of ¾” flexible liquidtight metal conduit (sealtight) that is routed to the fixture’s electrical box.
Inside of the sealtight is one #12 bare copper ground conductor and two #12 conductors that are spliced at the conduit body to the #10 conductors and at the fixture’s electrical box to the #16 or #18 fixture ballast leads.

The argument between the electrical contractor and the code inspector deals with the length of the sealtight and the conductors that lie within.

The electrical contractor considers the ¾” flexible liquidtight metal conduit and the circuits within to be branch circuits. As such there is no limit to the length of the sealtight and conductors between the conduit body and the fixture (within reason).

The code inspector states the ¾” flexible liquidtight metal conduit is limited to a 6’ length based on section 351-8 Exception No. 3 of the (1999 NEC) Code. He also states that the conductors within the ¾” flexible liquidtight metal conduit are to be considered tap conductors and are subject to section 410-67 (c) and are therefore limited to a 6’ length.

My take on the issue is that section 351-8 Exception No. 3 applies to the mounting distance requirements for flexible liquidtight metal conduit, not the length. I also feel that section 410-67 (c) applies to the smaller conductors that connect to the ballast that are not protected by the 20-amp circuit breaker.


ML

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#83388 - 01/30/03 08:48 AM Re: Branch Circuit or Tap?  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
351-8 ('99 NEC) is an exception to support intervals that permits fixture whips less than 6' long to be unsupported.
410-67 (b) allows branch circuit conductors with the appropriate temp. rating to terminate in the fixture. (c) permits just the final 18-72" to have the increased temp. rating.
Neither seems to offer a definitive on the interpretation of a tap. It seems a matter of personal interpretation on what constitutes a fixture tap.
Ask him if you were to change the #12 to #10, would he still consider it a tap?


#83389 - 01/30/03 09:34 AM Re: Branch Circuit or Tap?  
txsparky  Offline
Member
Joined: May 2001
Posts: 552
Magnolia,.Texas U.S.A.
Quote
Ask him if you were to change the #12 to #10, would he still consider it a tap?

Why would the inspector consider it to be a tap if it is protected by a 20 amp circuit breaker?You did'nt state whether or not the sealtite is supported or not.If it is,then 351-8 ex.3 would have no bearing on the installation.I agree with you that 410-67(c) applies to the fixture.


[This message has been edited by txsparky (edited 01-30-2003).]


Donnie

#83390 - 01/30/03 10:50 AM Re: Branch Circuit or Tap?  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
The #12s are not tap conductors because they are protected at their ampacity. The length of the sealtight is not limited if it is supported as required.
The #12 EGC is a violation of 250-122(b). This section requires the use of a #10 EGC for this circuit.
Don


Don(resqcapt19)

#83391 - 01/30/03 11:50 AM Re: Branch Circuit or Tap?  
txsparky  Offline
Member
Joined: May 2001
Posts: 552
Magnolia,.Texas U.S.A.
Don,
Good catch on the gound! [Linked Image] I overlooked it.


Donnie

#83392 - 01/30/03 12:07 PM Re: Branch Circuit or Tap?  
Michael Luersen  Offline
Junior Member
Joined: Jan 2003
Posts: 5
Bedford, Texas, USA
I just talked to the electrical contractor and he stated that they only used #10 awg for this job. That is #10 to the fixture and all #10 ground. Thanks for the feedback.


ML

#83393 - 01/30/03 12:10 PM Re: Branch Circuit or Tap?  
txsparky  Offline
Member
Joined: May 2001
Posts: 552
Magnolia,.Texas U.S.A.
Is the sealtite supported as required?Does the T condulets comply with the marking requirements of 370-28(3)?

[This message has been edited by txsparky (edited 01-30-2003).]


Donnie

#83394 - 01/30/03 01:43 PM Re: Branch Circuit or Tap?  
Michael Luersen  Offline
Junior Member
Joined: Jan 2003
Posts: 5
Bedford, Texas, USA
According to the electrical contractor, the sealtight is supported corrrectly and the conduit body is labeled correctly.


ML

#83395 - 01/30/03 01:50 PM Re: Branch Circuit or Tap?  
txsparky  Offline
Member
Joined: May 2001
Posts: 552
Magnolia,.Texas U.S.A.
The way you describe the installation (your last 2 posts) sounds code compliant to me.


Donnie

#83396 - 01/30/03 02:18 PM Re: Branch Circuit or Tap?  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
If those splices are made in a 3/4" conduit tee, I doubt you have the room for 7 #10s.
The tee is probably about 10 cu.in.
7 x 2.5 = 17.5 cu. in. required.


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