Electrical Services: Installing Lighting & L1/L2 Feeds

[brenfox]

I have been installing lighting from a 3 phase board. The wiring schematic has instructed me to place an l1 and l2 feed into the same switch box. Is this not bad practise? Would it be better to put 2 L1 feeds to it instead? Therefore there would only be 230v at the switch. Also , am i correct in assuming the potential across 2 L1 feeds would in fact be 0?

 

[davenn]

why are you dealing with these sort of electrical situations if you don't know what you are doing ??

Have you not received training for such ?
Why are you not under the supervision of some one qualified to work on these systems ?

A forum like this ISNT the place to be asking these sorts of questions

Regards
Dave

 

[dlgoff]

... am i correct in assuming the potential across 2 L1 feeds would in fact be 0?

Yes. However it's difficult to run something across two lines with the same phase.

 

[brenfox]

Answer to first question is yes, i do know what i am doing.
Answer to second question is yes, i have received training for such. This is why i am questioning what my engineer has instructed me to do.
Answer to third question is no, i am not under the supervision of anyone because i am more than capable AND competent to do the job.
Lastly, thank you for your response. I apologise for my apparent ignorance of my post and the wasting of your valuable time. Good day.

 

[sophiecentaur]

Answer to first question is yes, i do know what i am doing.
Answer to second question is yes, i have received training for such. This is why i am questioning what my engineer has instructed me to do.
Answer to third question is no, i am not under the supervision of anyone because i am more than capable AND competent to do the job.
Lastly, thank you for your response. I apologise for my apparent ignorance of my post and the wasting of your valuable time. Good day.

Before throwing the toys out of your pram, perhaps you should re-read your original question. It really doesn't look like it's from someone who knows as much as you claim to know. Imo, Dave's response was about right.
Did you mean "2 L1 feeds" or One :1 feed and a neutral?

 

[jim hardy]

It might be okay if voltage between phases is less than 300 volts.

See NEC 404-8(B)

and here's a couple articles that might relate to your installation

http://www.ecmag.com/section/codes-standards/voltage-between-adjacent-devices

http://www.lutron.com/TechnicalDocumentLibrary/048148a.pdf

It'd be worth spending a couple hours in the code book, maybe at home.

A fellow named "Mike Holt" runs a site dedicated to answering practical code questions like yours.

It's desirable to have lighting split among different phases so loss of one phase doesn't put everybody in the dark. But you haven't given much detail.old jim.

 

[Okefenokee]

To answer your first question, it's not bad practice, assuming you're using some kind of 2 pole single throw switch (DPST). The important thing is that a switch must de-energize a device. In cases where the device only uses a single phase and a neutral you only have the break the phase and can leave the neutral connected to the device since it should be at 0 Volts.

It's perfectly normal to connect lighting to two phases because phase-to-phase voltage is higher than phase-to-neutral voltage. If you use a higher voltage the lights will draw less current. This saves energy from losses in wires as well as money spent on wire.

Be safe and keep asking questions.

 

[sophiecentaur]

To answer your first question, it's not bad practice, assuming you're using some kind of 2 pole single throw switch (DPST). The important thing is that a switch must de-energize a device. In cases where the device only uses a single phase and a neutral you only have the break the phase and can leave the neutral connected to the device since it should be at 0 Volts.

It's perfectly normal to connect lighting to two phases because phase-to-phase voltage is higher than phase-to-neutral voltage. If you use a higher voltage the lights will draw less current. This saves energy from losses in wires as well as money spent on wire.

Be safe and keep asking questions.

The lights must have the appropriate working voltage of course.
Is the connection of lights across two phases standard practice? If so, which country? I don't think it's done in the UK.

 

[sophiecentaur]

It might be okay if voltage between phases is less than 300 volts.

See NEC 404-8(B)

and here's a couple articles that might relate to your installation

http://www.ecmag.com/section/codes-standards/voltage-between-adjacent-devices

http://www.lutron.com/TechnicalDocumentLibrary/048148a.pdf

It'd be worth spending a couple hours in the code book, maybe at home.

A fellow named "Mike Holt" runs a site dedicated to answering practical code questions like yours.

It's desirable to have lighting split among different phases so loss of one phase doesn't put everybody in the dark. But you haven't given much detail.


old jim.

You're talking here about redundancy (?): a good idea. You aren't talking about connection between phases - are you?

I still don't get what the OP is actually describing in his statements about connections to phases.

 

[Jobrag]

My first question would be, what voltage are the lights rated for?

 

[Okefenokee]

It's very common in the US sophie. Not in residential, which is single phase, but in commercial and industrial services that are 3-phase. Office and warehouse lights sold in the US tend to have ballasts (transformers) that can be tapped for 120, 208, 277, or 480V supplies.

Basically you buy a ton of them and have some electricians go through them all and set them up for the correct voltage then go to town installing them.

The circuit usually draws too much current for any kind of basic wall switch so you have to install a contactor that engages the lights. A basic wall switch can then turn the contactor on and off. Some people go the cheap route and just put a mini-switchgear in the electrical vault to turn the lights on and off.

Brenfox is probably wiring up a contactor for his engineer.

 

[jim hardy]

You're talking here about redundancy (?): a good idea. You aren't talking about connection between phases - are you?

Yes, redundancy. Myself, i'd only connect lights phase to neutral so as to avoid backfeeds when you lose a phase. Every room should have some lights from different phases.

I still don't get what the OP is actually describing in his statements about connections to phases.

Nor do i.
It'd be well for bren to brush up on the relevant sections of electrical code and educate his engineer, if necessary.

Could be he just assumed engineering school teaches practical matters like NEC.
I sure never had such a course.
Young engineers new to industry need to be taken under the wing of an old hand. I had a most excellent mentor. Our electricians and mechanics were always happy to answer my questions about the practical side of things.

old jim

 

[Averagesupernova]

Before anyone goes jumping to conclusions here you don't even know if the OP is working with live wires or will even be the one doing the connections once the wires are pulled into the boxes. I have known electricians who send their teenage kids out to the job-site to pull wires into conduit. Guess what? There is no power on the site. Later on when all the wires are pulled in someone qualified makes the connections in each box.

When the first response after the original post is this:

why are you dealing with these sort of electrical situations if you don't know what you are doing ??

Quite frankly I don't blame the OP for telling this forum to f*** off. It has always appeared to me that there are very few who post on here who have any real experience in actual electrician work. Oh yeah there are some of you who added an outlet or maybe even a whole circuit in their basement but compared to the project it seems the OP is handling you don't have a clue.

Edit: That is not to say there is no one here that knows anything about it, just typically not the ones who yell the loudest.

 

[Okefenokee]

I just had a thought that might help you on your second question Bren.

A voltage measurement is always the difference between two points.

At first that might seem like a subtle point but it's crucial.

Consider this example:

You're troubleshooting an outlet so you measure the voltage between the hot and neutral. You measure 0V so you think it's safe to open the outlet and inspect it. You get electrocuted. What do you think happened? The neutral was connected to the same phase as the hot! The difference between the phase and neutral is 0V because they're at the same potential but the difference from ground to neutral or hot was still 120V.

That's a true story. Investigating this I found that an electrician had connected the neutral to a 3-pole breaker in the panel in order to make a special 3-phase outlet in another part of the building. The electrician either didn't know or didn't care that the neutral also connected to two regular 120V outlets. So one outlet had 0V from phase to neutral and another had 208V. That 208V outlet burned up plenty of tools before I was called to look at it.

If I had measured the neutral to ground I would have immediately seen that it was energized. I could have used an NCV too (non-contact voltage tester). Keep one in your tool bag or your pocket. They only cost 10 to 15 bucks. It was totally my fault that I got zapped.

 

[sophiecentaur]

You could argue that this forum is not the vehicle for 'discussing' matters that are as clear cut as Wiring Regs. 'The Book' says it all.

 

[Averagesupernova]

You could argue that this forum is not the vehicle for 'discussing' matters that are as clear cut as Wiring Regs. 'The Book' says it all.

Not really. There are many places the 'book' is not that clear. Go here:
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http://forums.mikeholt.com/
-
If everything was as clear cut as you claim then those message boards would not exist.

 

[sophiecentaur]

Not really. There are many places the 'book' is not that clear. Go here:

-

http://forums.mikeholt.com/

-

If everything was as clear cut as you claim then those message boards would not exist.

You have a point but your link is the sort of forum to post such specialist queries. PF will give you much better and reliable explanations than the purely practical groups (on which you can read total scientific rubbish).
But don't expect PF contributors to know about part numbers and all abbreviations. That's not the Physics of the situation.

 

[MrSparkle]

Not really. There are many places the 'book' is not that clear. Go here:
-
http://forums.mikeholt.com/
-
If everything was as clear cut as you claim then those message boards would not exist.

I don't think I'd trust anyone to install lighting in my home or office who thought the lights would run with an electric potential of 0.

 

[Okefenokee]

Then you would be really disappointed if you went to a job site and talked to the young apprentices.

Electrical work isn't all Ohm's law and circuit theory. Apprentices start with making good pipe bends and pulling wire. Proper securement and good construction is every bit as important as knowing what conductance is. Apprentices learn as they go from their journeymen and masters who watch everything they do and answer all their questions.

It's actually pretty hard to achieve a journeyman license. It takes four years of on-the-job training in many places. It also requires some night classes and a tough electrical code test around here. It takes about 6 to 10 years to achieve a good masters license (in a state with high standards).

Believe it or not the system produces some pretty talented tradesmen and tradeswomen. It's well worth putting up with a few newbie questions.

 

[AlephZero]

There is no evidence here of the OP's qualifications. We have a question that (IMO, speaking as an engineer with no electrical training, but a lot of life experience reading between the lines and a BS filter that works pretty well) gives me the clear impression the OP doesn't understand the basics of what he/she is doing, otherwise the question wouldn't be necessary.

And the OP's next post (again IMO) is the classic example of the well known engineering equation

over-confidence in one's knowledge and ability + arrogant attitude = accident waiting to happen.

I don't know what is the US equivalent of the UK expression "cowboy electrician," but I don't believe you don't have any on your side of the Atllantic.

 

[Averagesupernova]

Aleph, it is clear to me that you don't understand what happens in the USA concerning electrical work in the manner that the OP is working. Okefenokee covered it pretty well. The OP is probably very well trained and capable of doing what he is supposed to be doing. What he is NOT supposed to be doing is designing the plan from square one. He is simply questioning something that is not part of his job. If this guy worked for me I would commend him for questioning things instead of shrugging it off. Read my previous post in this thread. I still stand by it 100%.

 

[Integral]

BrenFox, If you return and choose to reply to this tread, please report it to get reopened. I am closing it because you have not responded.

 

[ZapperZ]

Thread has been reopened.

Zz.

 

[brenfox]

Before i begin, what i will say is my OP could have been worded better. My wiring diagram showed 2 phases going into a 230volt 6 way grid switch, which was servicing 2 banks of lights on 2 separate feeds. This would equate to 415 volts at the switch. This, in my opinion is bad practise. The Regs was not helping on this matter so i decided to post it on here. In hindsight maybe this was a mistake to do so, but as a relative newcomer i was not sure on the protocol regarding what should and should not be discussed on here. I responded to Davnn curt comments with curt answers, which contrary to "expert" opinion i was not throwing my toys out. His comment was not helpful in the least except to try and make me feel stupid and incompetent. As a grown adult i simply will not put up with somebody speaking to me in this manner. Seeing as though you are all keen to know my qualification background i will inform you that i am a 17th edition qualified electrician with an ONC in electrical engineering who is currently studying for an HND at open university. I was sceptical about posting my questions on this site for a fear of being made to feel stupid. There seems to be a certain arrogance and a "you should know that" attitude with some people on here. Puts adult learners off from using this site.

 

[MrSparkle]

Did you put in a neutral line and not mention it? because with two of the same feed, you've got 0 power.

 

[brenfox]

Yes there are two separate neutrals for the 2 feeds. Everything works fine but my point to the engineer is that i do not like putting 2 feeds into the same switch box from different phases because there could be a potential of 415volts in the switch box when the switch box is only rated at 230 volts. What i wanted to do was take a line from L1 and another line from L1 on the 3 phase dis board, this would result in only 230 volts at the switch box. I have done an amp check on the incoming feeds and they are balanced so taking 2 L1 feeds do not upset the equilibrium if you know what i mean!

 

[brenfox]

Alephzero, your BS filter is faulty. Comparing me to a cowboy because of one poorly written post is both ignorant and insulting. Yet another example of an arrogant know it all. If you are an engineer with no electrical training then why are you commenting on an electrical question??

 

[MrSparkle]

Yes there are two separate neutrals for the 2 feeds.

ah. its not necessarily given that the neutrals were included and 3-phase doesn't necessarily include a neutral line, hence the confusion.

If you had a 3 story office building, and put one phase on each floor, but the 3rd floor works late every night, you'd have an unbalanced load. I can see the value of putting multiple phases into each switch box. As to whether that is standard industry practice, this is not the best place for that kind of question.

 

[brenfox]

Yes i have realized to my detriment that this type of question is not suited to these forums!

 

[jim hardy]

Yes there are two separate neutrals for the 2 feeds. Everything works fine but my point to the engineer is that i do not like putting 2 feeds into the same switch box from different phases because there could be a potential of 415volts in the switch box when the switch box is only rated at 230 volts. What i wanted to do was take a line from L1 and another line from L1 on the 3 phase dis board, this would result in only 230 volts at the switch box. I have done an amp check on the incoming feeds and they are balanced so taking 2 L1 feeds do not upset the equilibrium if you know what i mean!

Your original question, which was

Is this not bad practise?

is a good one.

NEC link i posted requires a physical barrier between switches if there's more than 300 volts between them. That's to protect flesh. But it says 'snap switches".
I am NOT an expert in code, and i don't know what your switches look like , but the links i posted should help you start figuring out whether your engineer has stayed within code. I didn't know about that 300 volt requirement before looking into your question.
I believe there are also requirements for color coding or marking the phases, too, and their neutrals if not all from same panel. Fortunately the code is well cross referenced. I'd have to spend at least a couple hours reading , probably you are more NEC-literate than I.

Keep your engineer out of trouble. My technicians used to tell me "Go calculate something while we take care of this."
We helped one another by sharing our strengths. If your engineer has any sense he'll appreciate your cross-checking . Keeps you both out of trouble.

Is that 415 volts line to line, or a line to Earth ?

I'd be curious to hear what you find .

old jim