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Posted By: Michael Luersen Branch Circuit or Tap? - 01/30/03 01:43 AM
[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.
Posted By: Redsy Re: Branch Circuit or Tap? - 01/30/03 12:48 PM
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?
Posted By: txsparky Re: Branch Circuit or Tap? - 01/30/03 01:34 PM
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).]
Posted By: resqcapt19 Re: Branch Circuit or Tap? - 01/30/03 02:50 PM
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
Posted By: txsparky Re: Branch Circuit or Tap? - 01/30/03 03:50 PM
Don,
Good catch on the gound! [Linked Image] I overlooked it.
Posted By: Michael Luersen Re: Branch Circuit or Tap? - 01/30/03 04:07 PM
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.
Posted By: txsparky Re: Branch Circuit or Tap? - 01/30/03 04:10 PM
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).]
Posted By: Michael Luersen Re: Branch Circuit or Tap? - 01/30/03 05:43 PM
According to the electrical contractor, the sealtight is supported corrrectly and the conduit body is labeled correctly.
Posted By: txsparky Re: Branch Circuit or Tap? - 01/30/03 05:50 PM
The way you describe the installation (your last 2 posts) sounds code compliant to me.
Posted By: Redsy Re: Branch Circuit or Tap? - 01/30/03 06:18 PM
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.
Posted By: txsparky Re: Branch Circuit or Tap? - 01/30/03 07:19 PM
Hmmm...Hubbell lists their 3/4 T condulets at only 7 cu.in.
Posted By: Michael Luersen Re: Branch Circuit or Tap? - 01/30/03 07:31 PM
I haven't checked this particular installation yet, but in their other conduit runs, they are using 1 1/4 condulets with RE bushings. The OZ 1 1/4 T condulet is listed at 32 cu. in.
Posted By: txsparky Re: Branch Circuit or Tap? - 01/30/03 08:50 PM
I didn't see anything in Bedford's Electrical Code that would limit the length of the flex.. http://livepublish.municode.com/17/lpext.dll?f=templates&fn=main-j.htm&vid=11924
Posted By: Michael Luersen Re: Branch Circuit or Tap? - 01/30/03 09:00 PM
txsparky,
Just to let you know, the work in question is happening at the DFW Airport. You aren't the electrical contractor are you??? [Linked Image]
By the way, I live in Bedford.....
Posted By: txsparky Re: Branch Circuit or Tap? - 01/30/03 09:45 PM
I got the Bedford from your profile and just assumed the work was in that general area.The airport may have stricter codes from FAA.Not sure though.
I'm in Spring,just north of Houston,but I'll be in Plano tommorrow.
Posted By: Redsy Re: Branch Circuit or Tap? - 01/30/03 09:51 PM
Why didn't they use j-boxes?
I believe using an oversized condulet poses problems of a different nature.
314.23? Exception?
Posted By: txsparky Re: Branch Circuit or Tap? - 01/30/03 10:35 PM
Redsy,I thought of the support issues with the oversize condulet but figured since the inspector didnt cite it,to let it go.
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