240 recep. phasing

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rsvetti

Member
Hey all. I have a question regarding the installation of 240v recepts. The sitch is as follows:

The plugs are to be installed from a 3 phase, delta power source. In the interests of space conservation within the panel, I was considering the usage of L2 and L3. Since the building was built prior to 1975, L3 is the stinger at 208v. Can this be done? I've been looking for a definitive answer and can't seem to find one.

The plug of course is powered by 2 hots and a ground. Can I use the high leg given the voltage between the two conductors equates to 240v or does some utilization equipment require both legs to be 120v to ground? This is an industrial application whereby the plugs will primarily be used for welders which "require ground". I'm not sure if I can do this in this case, other cases, or ever at all. If I can do this, under what conditions?

Thanx for your time,

RSvetti
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Re: 240 recep. phasing

Using L2 and L3 would be fine. The high leg voltage (208 volts) is between the "stinger" phase and the ground or neutral in a 3 phase 4 wire delta system. This will not affect your line to line connection. You could use L1-L2, L2-L3, or L1-L3.

[ June 28, 2005, 04:04 PM: Message edited by: infinity ]
 

rick hart

Senior Member
Location
Dallas Texas
Re: 240 recep. phasing

I don't have my code book in front of me so I can't verify if this is code or convention but, I recall that only 3 phase loads are to be connected to the high leg of a delta service. This is because this 3 phase system is a hybrid system between a large single phase service and a smaller transformer that only supplies the 3 phase expected load.
It will work and yes- it will be 240V across any two phases. Connecting a series of welders might not be a good idea though. The utility will likely frown on it.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Re: 240 recep. phasing

240V any be connected to any combination of phases. The NEC does not address the issue of unbalanced connections to a 240/120V delta system. The closest it comes is the requirement that equipment be rated for the voltage. Very little if any single pole North American equipment is rated for 208V to ground. Most equipment (especially standard two pole breakers) in the US is "slash rated" as 120/240V, so it can not be used on the high leg.

But, confirm any substantial phase-phase unbalance with the local POCO, they may have restrictions. And it is almost certain they would not like a 208V to ground connected load on the high leg.
 

rsvetti

Member
Re: 240 recep. phasing

Alright guys, I give. Who is this "Paco" guy that everyone's refering to (POCO)? At the risk of appearing grossly uninformed, bear in mind, I'm new to the forum.
 

rsvetti

Member
Re: 240 recep. phasing

Also too, thanx Jim, good answer. I should have realized. Any other underlying info you could give me on this sort of matter? I could always stand to learn more.

To start, whom is this "Paco" guy that everybody's refering to (POCO)? I'm new to the forum and don't recall the reference.

Other than that, I could stand to learn more about utilization equipment. If it's not a line to neutral load, isn't the fact that the meter reads "240v" enough, does the ground function as a nuetral in some cases? If not, I wonder if you could tell me why?

Thanx again,

RSvetti
 

rsvetti

Member
Re: 240 recep. phasing

Can anybody give me any other reasons that this might be a bad scenario (specific real-world descriptions please). Indeed, I'd like to get down to the bottom of this one. Being the book doesn't seem to have any real restrictions on the subject, I'd like to know what the boundaries are and why. This could really save alot of unecessary and unwanted work in the future.... Any input?
 

derf48

Member
Re: 240 recep. phasing

I think you need a little TLC in the area of voltage. It is not available in the NEC!!! There is very little time or effort spent in education of electricians today in this area. In fact, I do not remember reading an article in a national publication about voltage in the last 10 years.

Voltage is the pressure, the force, that moves the electrical energy from point to point. It is measured as a potential between two points. IEEE has established industry standards on how to reference or name voltages, but that is not followed enough in the real world to worry about now.

A 240 delta system is actually an ungrounded 240 volt 3 phase single voltage system. The only voltage present is 240, between any two conductors. It has no voltage to ground, that doesn't mean you can't measure any, but since it is an ungrounded system, it has no referrence to ground and therefore that measurement can be anywhere from 0 to 240 volts.

a 240/120 delta is a multi voltage system that has a center point grounded on one side of the delta. It has two voltages, 240 volts between any 2 of the phase conductors, and 120 volts between the "neutral" and the two phase conductors connected to that grounded winding. The voltage between the third phase conductor and the neutral is by theory about 208 volts, but is not usable because there is no way to keep it at 208 when a load is applied.

A 120/240 volt system is the standard "residential" voltage found in this country. It is a single phase, dual voltage system.

A 240 3 phase corner ground, not used extensively, is also another system that when you use your meter it will read 240. A 208Y/120 is another 3 phase, 4 wire system .

In the field you need to do a few things before you connect equipment. First, identify the system voltage. Second, identify the equipment requirement, and make sure the two match. Third, if it is cord connected, use a correct cord set for that voltage,phasing, and amperage. That info is not in the code, but is in the handbook, or usually hanging on the wall of most wholesale houses.

I wish I could give you a good place to study voltage but I do not know of one. I am sure a few of the hundreds who read this will know of a resource available.

Fred Bender
 

charlie

Senior Member
Location
Indianapolis
Re: 240 recep. phasing

240.85 Applications. A circuit breaker with a straight voltage rating, such as 240V or 480V, shall be permitted to be applied in a circuit in which the nominal voltage between any two conductors does not exceed the circuit breaker?s voltage rating.

This is just part of the Section, you need all of it for the proper application of circuit breakers. You are indeed permitted to take 1? power from either phase and the high phase. You will also tend to collapse the delta with too much load on the high phase and a third transformer will need to be added (assuming it is an open delta installation).

A lot of electric utilities will ask you how much 3? and 1? load you have in order to size their transformers. As a result, they are not expecting the high phase to get additional load and do not want you to use the high phase. I don't see how an electric utility can mandate that you do not use all of your service. That is just my personal opinion. :D
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
Re: 240 recep. phasing

Originally posted by rsvetti:
Can anybody give me any other reasons that this might be a bad scenario (specific real-world descriptions please).
How about a range? While the burners will work fine, the clock generally uses a hot and a neutral. It would be a shame to fire 208 across the range's clock. :)

Hey, check out this thread that I've been quietly playing with. I've found some informative information ( :p ) and am looking for more, as I remember and get time.
 

charlie

Senior Member
Location
Indianapolis
Re: 240 recep. phasing

How about a range?
George, this is a 240 volt delta. A range is a 120/240 volt, 1? appliance and is not permitted to use the high phase. The same thing applies to a dryer. However, any straight 240 volt, 1? equipment may go from the high phase to either of the other phases with impunity. :D
 

rsvetti

Member
Re: 240 recep. phasing

Right... so, I understand this all thus far. However, I am not entirely clear.

In regard to utilization equipment, 240v across 2 phases is the only requirement provided the a neutral is not present or utilzed? To the best of anyone's knowledge, is the ground conductor ever utilized as a grounded conductor by the equipment? If so (or otherwise), does any of this equipment utilize the sole potential of one leg without a neutral? If it does utilize 120v (without the neutral), would this configuration have adverse affects?

In a 4 wire delta system, is the stinger 208 volts relative only to ground or in regard to line to neutral loads? Hmmmmm.....

Anyway...

From what I understand, the high leg is in reality, no different from the other two legs except in regard to the neutral (being landed so far from the termintion of the transformer. This, in conjunction with the lack of prohibition of this configuration, leads me to believe that I can safely and legally save space in my panel by utilizing the high leg in 240v applications wherever a neutral is not present.

Voltage ratings of equipment, terminals, whatever are of course, always a concern. However, with no grounded conductor present, I see that there can be no viable concern.

...Any rebute from the know it alls? I want to here from the know it alls! Come on, I know you're out there. CAN ANYONE HELP ME?????

-RS :D
 

rsvetti

Member
Re: 240 recep. phasing

Whoah, sorry, typo. ------> Midpoint of delta GROUNDED, not connected to GROUNDED CONDUCTOR via any other means than bonding at the main. I know, I know....

BTW, I'm with Charlie...
What does "Paco" have to say about it anyway???

[ June 30, 2005, 04:13 AM: Message edited by: rsvetti ]
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
Re: 240 recep. phasing

Originally posted by rsvetti:
To the best of anyone's knowledge, is the ground conductor ever utilized as a grounded conductor by the equipment?
RS, see 250.6. The grounding system cannot carry "objectionable current."

Also, see 310.2(A):
310.2 Conductors.
(A) Insulated.
Conductors shall be insulated.
Exception: Where covered or bare conductors are specifically permitted elsewhere in this Code.
All conductors are required to be insulated. Grounding conductors are specifically permitted not to be insulated by 250.119. Therefore, bare conductors (after the service) are "labeled" grounding conductors, and are unsuitable for carrying neutral current back to the source.

If so (or otherwise), does any of this equipment utilize the sole potential of one leg without a neutral? If it does utilize 120v (without the neutral), would this configuration have adverse affects?
A circuit must have a complete path to operate equipment. There is no way for a utilization equipment to function, using only one hot and no neutral. This configuration is commonly known as "Off." :)
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Re: 240 recep. phasing

Any breaker connected to the high leg must be rated for a straight 240V (i.e. SQD QO2---H. Normal 2 pole breakers are slash rated 120/240V (i.e. SQD QO2--) and can not be used on the leg that is 208V to neutral and ground.

Other than that feel free to use the high leg as you want. But, I would still discuss large un-balances with my power company.
 

rsvetti

Member
Re: 240 recep. phasing

Hey all, something for two of you.


Charlie:

"However, any straight 240 volt, 1? equipment may go from the high phase to either of the other phases with impunity."

Thanks, this is what I thought. So, this type of thing is okay assuming the recept. is dedicated?


Charlie:

Number 1.) Rest assured Charlie. My favorite code (assuming that any of us really have one) is ART 110.12. And I seemingly unlike those around me, am aware that this article is not confined to the 'mechanical' aspects of the trade (assuming that any of them have read it ...apparently not).

2.) I'm not at home; I'm visiting with my mother in Texas and my books are in Cali. Though I can tell you that (to my spurred recollection) that I realize yes:

Charlie -

"250.8 Connection of Grounding and Bonding Equipment. Grounding conductors and bonding jumpers shall be connected by exothermic welding, listed pressure connectors, listed clamps, or other listed means. Connection devices or fittings that depend solely on solder shall not be used. Sheet metal screws shall not be used to connect grounding conductors to enclosures."


was the line I was thinking of. In fact, now that I recall, the part about "two threads" was an FPN, an elaboration (speculation/opinion) (I own the handbook), or something. I didn't think that was actual code...

I'll be returning mid next week.

To tell you the truth, its getting pretty late again and I've really only had a chance to jump around through these threads.

3.) RSvetti -

"Whoah, sorry, typo. ------> Midpoint of delta GROUNDED, not connected to GROUNDED CONDUCTOR via any other means than BONDING AT THE MAIN. I know, I know...."

4.) Being that I'm visiting with Moms, I am trying not to go too in depth into the forum. After all, this is supposed to be a vacation... As such, I probably missed that thread you're talking about. However, you guys seem to know your stuff; this is refreshing. I'll definately be checking this out a bit more when I get home. BTW, which thread was that anyway (the one that you wrote to me)?

5.) A glimpse into me:

My name is Robert Stiavetti, born January 8, 1980 (June 30, 2005) in California where I have lived all of my life. I am twenty five years old and have lived (for the most part) independently since the age of twelve (yes, twelve).

Pertinent to the trades, I have been "another day older and deeper in dept" for the past seven years. Of those years, my experience varies. I was a "skilled laborer" learning alot about pain and building for the first year or so (half of that time I spent as an apprentice to most things construction, outside of plumbing and foundations [I had a bad experience once] and as
supervisor to labor crews.
After this, I decided to narrow my scope a bit and was a general carpenter, electrician (mostly carpenter) for the next three years.

Please see: I am the AHJ, note on drywall screws> :D

My partner and I then decided to split trades (long story): he would focus solely on the carpentry end of our grand master plan, and I would focus solely on electrical. Hence wither, I became an "electrician" (now of about an exclusive three or so years experience). Combined, I would gather I am an electrician of about four years. Unfortunately, most of that is exclusive to residential (due to the grand master plan).

As a result, I admit I am not the strongest in theory and actually just beginning to get more confortable with the heavier industrial applications, but am fairly certain that I can hold my own. That, and when it comes to the code, I have a fairly sturdy working knowledge. I will also admit that the properties of magnetism still elude me. Lets face it, flux is still somewhat of a mystery.

6.) Insight into the situation:

The guy has signed a ten year lease and owns only Welders @ 240v (as far as utilization equipment on wheels go). He promises to plug nothing else into these holes.

I've heard that modern wire lives about forty years. I'm with you; it's a bad idea (mostly).

Just so yah know, this is a followup on some very serious hacks that have no bussiness playing with fire.

Plugs are rated at 50a.
Overcurrent protection is at 30a.
Wire is way oversized for potential future applications and bungling idiots at a number 6.
And the pipe is 1 1/4.

Sew me Charlie, the terminal on the little plug thingy said "green" next to it. :D

7.) A torrid glance at the S@*t I see everyday:

BTW, that guy with the cover plates is either f$cki$g rich or extra terrestrial man! :D )(Authority Having Jurisdiction :D

-RSvetti

P.S. Utilization equipment is plural ;)

Edit: I'm sure this thing is full of typos.
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
Re: 240 recep. phasing

Originally posted by rsvetti:
Thanks, this is what I thought. So, this type of thing is okay assuming the recept. is dedicated?
What do you mean? The circuit doesn't necessarily have to be dedicated.
Rest assured Charlie. My favorite code (assuming that any of us really have one) is ART 110.12.
Not to pick on you, Robert (may we call you "Rob"? There's a lot of Bob's around here :)

Combined, I would gather I am an electrician of about four years. Unfortunately, most of that is exclusive to residential (due to the grand master plan).
I feel your pain. Stick around here, at least there's smarts to be found, if not hands-on. I have about 2.8 seconds of commercial, but being around here and listening helps a lot.

Bearing in mind that I am always open to criticizm and willing to share a bit about myself.
No kidding? I haven't seen a rant like that since MC hit his prime! :D

Two requests:

1. Try using the :p
 
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