314.28 (A) interpretations

[EE_rookie]

I have a 480v, 20A, 3 phase, lighting circuit - each fixture is 277V. A 2" conduit runs the length of the entire lighting layout, with junction boxes (12"x12"x6") located at each fixture to tap one of the hots, neutral, and ground, with the fixtures alternating even between phase A, B, and C and running 3/4" flex conduit to each fixture. Due to large voltage drop calculations, the 5 wires (A,B,C, N, G) are #2 AWG running the length of the lighting circuit, with taps/splice at each box to #10 AWG down to the fixture.

This is where the disagreements begin:

Contractor is saying:
1) The installation is against code (NEC 2017) because it should be an 8x the largest raceway and should be 16" long because 2 of the 5 wires are not being spliced in each box, despite being part of the same circuit.
2) The "splice" is not really a splice because they're using insulation piercing connections - therefore it's a straight pull.

Questions:
1) If a 3 phase circuit has 3 of it's 5 wires tapped in each box, would it be treated as a straight pull box (8x) or splice box (6x)?
2) Is the insulation piercing connection not considered a splice?

My thoughts/interpretations:
1) Because it's a single circuit, it's a splice box, not a straight pull. If it were multiple circuits where one entire circuit just passed directly through the box, then it'd be a straight pull box calculation.
2) There's not a definition for splice in Article 100, but 110.14(B) Splices mentions "conductors shall be spliced or joined with splicing devices identified for the use.." (i.e. insulation piercing kits)
3) If the box should be a straight box, which I disagree, the box still meets code by way of 314.28(A)(3): 5#2 AWG wires takes up .59in² which per the tables of Chapter 9, mean in theory we could have installed a 1 1/4" conduit instead of 2" and 1.25" x 8 = 10" and a 12" long box would be code compliant - am I interpreting that section correctly?

Thanks in advance code gurus!

 

[infinity]

I see two options, change the raceway to 1.25" and keep the 12X12 box or install the proper size box with the 2" raceway as the sparky has suggested.

 

[petersonra]

Is the idc listed as a comnector?

 

[Carultch]

Questions:
1) If a 3 phase circuit has 3 of it's 5 wires tapped in each box, would it be treated as a straight pull box (8x) or splice box (6x)?
2) Is the insulation piercing connection not considered a splice?

I believe it is overkill that they make you go by the raceway size, instead of the minimum permissible raceway for the conductors contained. One example where you would see this, is when a rough-in electrician installed a 2" conduit provision for future use, and you come back in the future to use it for a circuit that only requires 1.25". The logic behind this rule should allow you to use 1.25" for your calculations, rather than 2". But the rule we have, would govern 2" used in the calculation. The work-around for it, is to use a reducing bushing/close nipple, and locally downsize the oversized raceway where it connects to the box.

The intent of this rule is in regards to the mechanics of pulling conductors, all the way out of the box, and then straightening them back, when pulling through the second portion of the run. When you make a straight pull, the conductor has to enter, bend out of the box, bend back in to the box, and bend in to the exit raceway. The conductor makes a total of 4 quarter turns, that must be pulled back to straight. Angle pulls by contrast, only need to make 3 quarter turns, as you route the wire out of the box, back in to the box, and in to the exit raceway. The radius of each of these quarter turns, is generally about twice the trade size of the raceway, when filled to capacity with a typical single circuit worth of wire.

When using IPC's (insulation piercing connectors), also known as "bug bites", the main conductor is first pulled as if the tap conductor doesn't even exist. It is installed as a factory continuous conductor through this box. Putting in a splice allows you to separately pull each section, which is why you can shorten the dimension of the box compared to what it would be as a straight pull. The tap conductors are installed after the main conductor is already in place. So the box would need to be sized as if it were a straight pull, for the main conductors, when using IPC's to install the tap.

Switch from IPC's to insulated tap/splice blocks (Polaris multiport connectors or similar), and it can count as a splice.

If any conductor in the raceway is factory continuous between two raceways on opposite sides, it would count as a straight pull. Even if 3 out of 5 of the conductors land on a 3-terminal Polaris block, while the remaining 2 are factory continuous.

 

[EE_rookie]

I believe it is overkill that they make you go by the raceway size, instead of the minimum permissible raceway for the conductors contained. One example where you would see this, is when a rough-in electrician installed a 2" conduit provision for future use, and you come back in the future to use it for a circuit that only requires 1.25". The logic behind this rule should allow you to use 1.25" for your calculations, rather than 2". But the rule we have, would govern 2" used in the calculation. The work-around for it, is to use a reducing bushing/close nipple, and locally downsize the oversized raceway where it connects to the box.

The intent of this rule is in regards to the mechanics of pulling conductors, all the way out of the box, and then straightening them back, when pulling through the second portion of the run. When you make a straight pull, the conductor has to enter, bend out of the box, bend back in to the box, and bend in to the exit raceway. The conductor makes a total of 4 quarter turns, that must be pulled back to straight. Angle pulls by contrast, only need to make 3 quarter turns, as you route the wire out of the box, back in to the box, and in to the exit raceway. The radius of each of these quarter turns, is generally about twice the trade size of the raceway, when filled to capacity with a typical single circuit worth of wire.

When using IPC's (insulation piercing connectors), also known as "bug bites", the main conductor is first pulled as if the tap conductor doesn't even exist. It is installed as a factory continuous conductor through this box. Putting in a splice allows you to separately pull each section, which is why you can shorten the dimension of the box compared to what it would be as a straight pull. The tap conductors are installed after the main conductor is already in place. So the box would need to be sized as if it were a straight pull, for the main conductors, when using IPC's to install the tap.

Switch from IPC's to insulated tap/splice blocks (Polaris multiport connectors or similar), and it can count as a splice.

If any conductor in the raceway is factory continuous between two raceways on opposite sides, it would count as a straight pull. Even if 3 out of 5 of the conductors land on a 3-terminal Polaris block, while the remaining 2 are factory continuous.

Interesting tidbit about the mechanics of pulling conductors, it always seemed like it was backwards, the 6x for splices and 8x for straight.

Doesn't 314.28(A)(3) permit me to use a 2" conduit in a 12"x12"x6" straight pull box since the actual conductors are less than 20% fill? and I could use a 1.25" conduit. I'm not sure how to interpret (A)(3) otherwise.

"Listed boxes or listed conduit bodies of dimensions less than those required in 314.28(A)(1) and (A)(2) shall be permitted for installations of combinsations of conductors that are less than the maximum conduit or tubing fill permitted by Table 1 of Chapter 9" - NEC 314.28(A)(3)

 

[jusme123]

Is the bod listed AND permanently marked with max number and max size of conductors permitted?

I would just leave everything as you have it, and splice all the circuits ( hots, neutrals, grounds) inside every box.

Might cost you a little wire, but learn from it and move on.

 

[infinity]

Doesn't 314.28(A)(3) permit me to use a 2" conduit in a 12"x12"x6" straight pull box since the actual conductors are less than 20% fill? and I could use a 1.25" conduit. I'm not sure how to interpret (A)(3) otherwise.

No. The fact that your conduit is oversized is irrelevant to the box size calculation. If you can find a box with permanent markings that jusme123 referenced to permit less than the required 8X length then you could do it.