Cable splice

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siva

Member
Hi All
I have one branch circuit of 230 v,50 hz having 60 Nos of 32 watts lights.circuit run is about 500 feet total, including 200 feet home run(to DB). According to our specs "if total circuit run is more than 200 feet,wire size shall be 10 AWG other wise 12 AWG.my question is "Can we run the home run 10 AWG(about 200 feet) then splice it to two branch circuits of 150 feet each with 12 AWG wires.is NEC will allow this type splice(splice with two sized wires)..?
Thanks in advance
Siva
 

siva

Member
Re: Cable splice

hi
Yes .this is 100 % serious circuit.the ckt is using for US Naval Base.I just want to confirm that this type of splicing is approved by NEC.
Thanks
Siva.
 

rattus

Senior Member
Re: Cable splice

Siva,

Some of the pros might tell you about the legality of the splice, but I would think it would be OK as long as the breaker is sized for #12, but I would think the main concern would be the voltage crop in a long run such as this. Sounds like they want all of it to be #10.

This reminds me of a situation we had in the Army. The Signal Corps. used something called "Spiral Four" which was a fat cable carrying four small gauge conductors. Someone decided to use it for 120v AC, and it was OK for light loads, but with a heavy load, the voltage at the end of 100 ft. sagged to about 60. Be sure you size the cable adequately.
 

coulter

Senior Member
Re: Cable splice

siva -

I'm not questioning if the ckt is a real application - I had assumed it was. What I am asking is if the 60 each, 32W lights were in series as opposed to parallel.

32W isn't much light, and I can't guess the application.

So, with the information I have, here are my Assumptions about the ckt:

1. 200 feet of 2C - #10 to a junction box

2. From the J-box, two parallel circuits, 150 feet of 2C - #12

3. Load at the end of the of each ckt is 30 each - 32W lights - 960W


Analysis:

1. 60 each at 32W = 1920W

2. Current in the #10 = 8.3A

3. Vd over the 200 feet of #10 (400 feet round trip) = 8.3 X 1.24 X 400 / 1000 = 4.1V

4. Current in each parallel #12 ckt is 4.2A

5. Vd over the 150 feet of #12 (300 feet round trip) = 4.2 X 1.98 X 300 / 1000 = 6.7V

6. Total Vd to the load is 10.8V. Less than 5% (the 5% is not a code requirement - but still a good idea)


This is going to work fine. You will have to use a 20A OCPD to protect the #12.

As far as the splice to smaller wire goes, there isn't anything in the NEC I know of that says you can't.

One other issue, is if you have an equipment grounding conductor in the raceway. Up-sizing the main conductors for voltage drop also requres you up-size the EGC.

carl
 
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