WIRING OF LIGHTING FIXTURES

[bench892]

What is the proper wiring of lighting fixtures? I am using a three phase power source, the layout shows three lighting branch circuits using a common neutral. Is this according to code? Or should we run separate neutral wires for each branch circuit?

[ August 13, 2003, 04:55 PM: Message edited by: bench892 ]

 

[bennie]

Re: WIRING OF LIGHTING FIXTURES

I am curious... What is the profession that you are acting as a consultant.

I don't intend to be rude, but your question is a fundamental of the trade.

 

[sparky46514]

Re: WIRING OF LIGHTING FIXTURES

Bennie--His profile states that he is a student.Unsure of what kind of student he is.I think that he should check his reference books or ask his instructor.

 

[renosteinke]

Re: WIRING OF LIGHTING FIXTURES

This question isn't as simple as it appears.

While it is permissible to have such multi-wire branch circuits, it may not be wise.
There is the issue of "harmonics," especially if the lights involved have electronic ballasts. In that case, it may be advisable to use an over-size neutral.

How do you know if there is a harmonic problem? I suggest running one circuit, with an oversize neutral. Power it up. Compare the readings from a "standard" and a "true RMS" ammeter. If the "true" reading is more than 15% over the other, there are harmonic issues that need to be addressed.

 

[bennie]

Re: WIRING OF LIGHTING FIXTURES

Reno: Have you seen many neutrals that have melted down from harmonic current?

 

[don_resqcapt19]

Re: WIRING OF LIGHTING FIXTURES

Has anyone actually found a problem on a multiwire branch circuit serving non-linear lighting loads that was conclusively proved to be caused by the harmonic current? Multiwire branch circuits have been and still are the most common connection for these types of loads and I have never seen or read about any problems on lighting circuits that were caused by the harmonic current.
Don

 

[bphgravity]

Re: WIRING OF LIGHTING FIXTURES

I think the question is more of power quality issues than one of direct problems with neutrals or equipment when dealing with harmonic conditions. Some engineers and facilities are more concerned with power quality and efficency than they are of hazards and dangers. (Just my opinion)

 

[brian john]

Re: WIRING OF LIGHTING FIXTURES

Ren and bennie:

Harminoics are a catch phrase that are thrown at every problem like it is the GROUND.

While I have seen harmonic issues, hot neutrals (branch circuit and feeders) overloaded transformers, and voltage distortion issues generators that have major voltage problems, one printing company was messing with his neighbors sensistive equipment. So there are harmonic problems. BUT
I have never seen a multi-wired lighting branch with an overloaded neutral WHEN PROPERLY INSTALLED. Not saying it can't happen, just haven't seen it.

Just from my exiperence.