IMO, it would not count as a CCC when supplied 120/240. The neutral still carries only the unbalanced current. Current attributed to the 240V portion of the load is balanced current, right?. Therefore, only the 120V portion can unbalance the load, and the neutral carries only the unbalanced portion of the circuit.
wire sizing
- Thread starter Ivan Young
- Start date
- Status
Ivan Young
Member
- Location
- Simpsonville, South Carolina
Thanks for all the replies guys. I am totally confused now. Some are saying the neutral should be counted and some are saying no. Which is it?
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
It it is supplied by a 120/240 single phase supply it is not current carrying. It it is fed from a 3 wire circuit supplied from 2 phases and a neutral of a 3 phase 4 wire 208/120 system then it is current carrying. See 310(B)(5).
Ivan Young
Member
- Location
- Simpsonville, South Carolina
Thanks Texie. I know that when lights are involved then the neutral must be counted
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
That's not always true-depends on the type of lighting. See 310.15(B)(5)(c). While you are there, look at 310.15(B)(5)(b) to help understand what I said in my previous post.
Ivan Young
Member
- Location
- Simpsonville, South Carolina
Perhaps you are using a 2011 code book but mine is a 2008 and there is no 310.15 (b)5(b) or 310.15 (b)5(c) but there is 301.15 (b)4(b) and (c). It says if you are using two phases and a neutral of a four wire , 3 phase , wye connected system, the neutral shall be counted. Aloso (c) says in a four wirte, 3 phase wye circuit where the major portion of the load consist of non linear loads (computers,lights,etc.),harmonic c`urrents are present in the neutral conductor, the neutral shall be counted.
Yep! Always true regardless of load type.
In the case of lights, only electronic-ballasted lights are non-linear. Incandescent and magnetic-ballasted lights are linear loads. Non-linear loads on split phase systems (i.e. 120/240V 1? 3W) under current code are not considered.
Last edited:
kwired
Electron manager
- Location
- NE Nebraska
Understanding some electrical theory explains why this is required.
In the case of 2 phases of a wye system and line to neutral loads - the neutral is not carrying imbalanced current like it is in a single phase system or a delta system, it is carrying approximately same current as highest loaded phase, therefore the conductor will contribute approximately same amount of heat within raceways and cables as does each ungrounded conductor.
In the case of non linear loads and wye supply systems the harmonic currents on a two wire circuit are the same in both wires. In a three phase wye system and line to neutral loads the harmonics are additive in the neutral and you can have more current resulting in more heat in the neutral than you have in any individual ungrounded conductor. Even with services and feeders.
Ivan Young
Member
- Location
- Simpsonville, South Carolina
Yes gentlemen, you are correct, it depends on the type of lights involved. Incandescent does not cause harmonics. Fluorescent with electronic ballast does that and I believe those lights that are used in warehouses sodium halyde but I am not sure.
kwired
Electron manager
- Location
- NE Nebraska
You mean high pressure sodium? Those are easily distinguished from all other light sources. They are the ones that have the yellow-orange color to the light and are very common for outdoor lighting especially roadways.
Ivan Young
Member
- Location
- Simpsonville, South Carolina
Yes those are the lights. They give off a lot of heat and when you turn them off even with leather gloves you have to wait a long time before you can touch them.
Do they cause harmonics?
Do they cause harmonics?
- Status