I have some questions regarding 3 phase electrical service. For the first time I’ve encountered what I believe to be a 3-phase service. My job was to add a SP 20A 120V circuit to power a Neon light transformer in a pizza shop. Upon seeing the service was a 3 phase I opted to not do the job since I didn’t know what I was dealing with, and to get educated and then decide if I feel ok enough to complete this part of the job. I’m perfectly comfortable working in a normal residential service panel and am confident in knowing what I am doing in such panels. Perhaps a 3 phase is not all that different and that’s fine if so. But, better to be educated first and not assume.
I believe the box was 3 phase because I saw 4 wires in the box powering the bus bars, one taped blue, red, black and white. White of course was on the neutral bar. I also noticed the exiting breakers had 3 poles. Having never seen this before, it looked rather interesting.
Anyways, my questions are as follows, some are curiosity ones:
- What is a 3 phase service, why have one, is there some advantage?
- What situations REQUIRE a 3 phase service?
- Can I power a SP 20A breaker (120v) from a 3phase panel? If so, how, just hook it up as I normally would do?
Replies
I'm almost never one to say this, but if you have to ask . . .
Here's the engineering major's version of 3 phase power:
http://www.ece.msstate.edu/~hagler/ece3144/notes/3phase/3phaseadvantages.xml
Here's an explanation with more english and less math:
http://www.du.edu/~jcalvert/tech/threeph.htm
Here's the english only version: ;-)
http://en.wikipedia.org/wiki/Three-phase_electric_power
You might like to futz around with the simulation to get a better idea of how it works:
http://www.powerstandards.com/PQTeachingToy/
Like I said, I almost never say this but if you have to ask, it's time to get some hand's on help from someone local who can show you the ropes.
"Let's get crack-a-lackin" --- Adam Carolla
Edited 5/23/2006 12:27 am ET by philarenewal
Only 2 possibilities here:
1. Willie is NOT an electrician, in which case he cannot legally do ANY electrical jobs for hire, 3-phase or otherwise.
2. Willie IS an electrician, in which case he's a really, really bad one and should be looking for a different career.
DG/Builder
What States require licensing for residential electrical? No licensing for residential electric in Ohio....of course, it's your BASS if you burn someone's house down, but that's another story...
What States require licensing for residential electrical? No licensing for residential electric in Ohio....
How about this:
http://www.contractors-license.org/oh/Ohio.html
Also, if you were paying attention, he was talking about a pizza shop. In most states, pizza shops are NOT residential. Then again, things may be different in Ohio...:)
DG/Builder
You do not need a license to do residential electrical work in Ohio. You do need it for a pizza shop as that is considered a business and falls under commercial. DanT
You guys don't need liscenced electricians for residential down there?
We do up around Toledo.
I do know that building regs are real spotty all around Ohio.
Aren't you north of Columbus? I would have thought that anywhere near a large city would be up to speed.
Remodeling Contractor just on the other side of the Glass City
Nope. We only need a permit in Marion county for septic systems or new construction waste piping. Nothing else. It is a terrible way to work but I will keep at it. :-) DanT
OMG you are soooo lucky.
I know you do a lot of kitchens/ baths etc.
If you were up here you would have to sub a elec, plumber for EVERY job - no matter the size, assuming you wanted to be above board.
I can't do a bath or kitchen, pull a permit, and even relocate a frickin outlet or hook up a new plumbing fixture.
I could go on for hours ranting about the code up here that was written/ enforced for new construction and has no provisions for remodelling.
Remodeling Contractor just on the other side of the Glass City
Cal I"m about 15 miles south of Dan (still waiting for you to stop for a beer) and if it isn't a home owner, you have to have a license in Delaware & Delaware county. Go further south to Columbus , Franklin county or the burbs it's the same thing. ALL comercial work in the state has to be done by a state licensed electrician And any project requiring a blanket permit must carry a stamp from either an architecht or an engineer.
Man if you would fill out your profile I would have some idea of where you are. I am busy as hell right now but things settle a bit maybe we can do that. If you work in Delaware County you must have the patience of jobe. Most consider it the black hole of unique code issues lol. DanT
Dan there is the possibilty a burb that may be hosting a golf tournament right now is trying to surpassDelaware county in creative interpritation of the electrical code. At least that's what I heard:) . When things settle down? tha may be when I'm dead at this raTE
I forgot to add, think 315 & 23, about 200 yards from my house.
I'll never move to Ohio!!!
Given this statement, "I opted to not do the job since I didn't know what I was dealing with.." seems that, regardless of his qualifications, he is wise enough to know when to say "no".
Thank yoiuIf at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
dg.....
Thanks for the wonderful compliments. I'm NOT an electrician as a career, but I do PLENTY of electrical work as part of my home improvement business. For you to say I cannot do any electrical work for hire is a little bit presumptuous of you is it not? For what it is worth to you, I'm allowed to do any kind of electrical work as I want,even commercial, without being licensed because the requirement is I get an inspection and pass. If I pass, no one cares diddly squat if I'm licensed or not. And, I've done a fair share of commercial applications which were similar to residential, and not a single township, or inspector, or anyone, said I could not. Plus, OJT is the best experience than reading books. I'm a self-teacher and self-learner, who has taken years to learn what I know and I do it quite well. It doesn't make me any less of a contractor because I am not licensed, nor does it make me any less of a provider for my family. Thank you.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
Another thing to be careful is that there are a number of different types of 3 phase services.This shows the two most common for light commercial/industrial.http://www.phaseconverterinfo.com/phaseconverter_delta_wye.htmThe 120/208 wye connection is also used for some larger homes. Many motors (AC) or sepected to work on either 208 or 240. Likewise heating elements (stoves, driers, WH) can work on either but there power output is greatly reduced.The 120/240 delta would be used at a place like a machine shop where most of the loads are motors and only minor 120 service is required.Large office buildings might have 277/480 wye service. The AC's work off the 480 2 phase. Flourscent lights have ballast that will work off the 277 line to neutral. 120 is provided by local transformers.You asked about phasing.For 120 loads you do it just like 120/240. You balance the loads between the different legs. Heating loads don't care about the phase sequence.On motor loads the sequence is important. Reverse any two connection and the motor direction is reversed.
Bill, thanks for the link and the info. That was most helpful to say the least. I'll have to re-review everything and see what I would have been dealing with.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
I see that you knowledge of licensing requirements is the same as your knowledge of electromagetic properties.That is non-existing.There are 6 states that have no state wide requirements.http://www.electric-find.com/license.htm
In this day and age, why would 6 states still not require licensing for such a skilled trade?
Why should they?BTW, here is someone that things the HO should be writing the codes.http://www.poorcodes.com/poorcodes/index.php
I think his title is poor and attacking codes in a general way with his attitude shows his lack of knowledge of where they protect the consumer in more ways than one. But.......
Codes have not really addressed energy issues very well (at least up here). I was an energy regulator for 9 years before I went private again (laid off when oil was $10/barrel just 6 years ago!!). Before that I was in home inspection, indoor air quality and ran an energy retrofit company...so you see that energy conservation is close to me.
For example, the current National Building Code of Canada has no minimum insulation levels in it. It states that walls separating conditioned spaces from the outdoors shall "have sufficient thermal insulation to prevent moisture condensation on their room side during the winter and to ensure comfortable conditions for the occupants" With this, we can put next to no insulation in a wall, turn up the heat and meet the code requirements.......poor....very poor!
Another example: The code does address air leakage with an intent that homes be tighter but doen't give code inspectors any way to confirm the airtightness. That's like police not having a radar and breathalyzer when they catch a drunk speeding. How you gonna get a conviction??
Anyway, getting off topic here. My 2 cents on energy regs!!
>>"In this day and age, why would 6 states still not require licensing for such a skilled trade?
If you get a permit and pass inspection, for routine residential work, anybody can do it. What's the rocket surgery?
Don't know what it's like in Canada, but around these parts, the licensee makes the money, their laborers and apprentices do the work. I don't have an electrician's license, but I can and do produce higher quality work than many of the "electricians." Still have to pay one to pull the permit though. Nice racket.
"Let's get crack-a-lackin" --- Adam Carolla
Maybe the inspectors have the time to inspect in your area. Inspected a $250,000 new home a few weeks ago in which the work was done by certified trades and inspected by certified inspectors- found 3 electrical, 1 plumbing and 1 ventilation code violations- this house had its occupancy permit and was ready to move into.
Now, granted a homeowner will try to do better work than some tradesmen but that is usually not what happens due to inexperience. So if the inspector is not picking up the few misses of trades, will he do a better job on a homeowner's job where there are likely to be more deficiencies.
I feel the more the homeowner gets involved in the more serious trades (where failure can lead to catastrophe-uneven drywall finsih is not the same as electric shock, fire or carbon monoxide gas), the more problems we'll have. These things are getting more complicated, not simpler.
>>"I feel the more the homeowner gets involved in the more serious trades (where failure can lead to catastrophe-uneven drywall finsih is not the same as electric shock, fire or carbon monoxide gas), the more problems we'll have. These things are getting more complicated, not simpler.
I'm talking about remodelers and rehabbers. Where I am, plumbing and electrical both need a license to pull a permit. For residential work, it's stupid.
The best electrician and plumber likely does better work than I do. The average, based on what I've seen -- I run rings around them. Still have to pay one to pull a permit for me.
On the HO side, since a HO can't pull a permit, they do their own work and it never gets inspected. For some, that's the recipie for disaster. Like I said, it's stupid.
EDIT: PS, got your web site link. Very nice site. I'll be up in Halifax this summer (my better half is Canadian). You should post that link in your signature line. Seems like very thorough site.
"Let's get crack-a-lackin" --- Adam Carolla
Edited 5/24/2006 8:10 am ET by philarenewal
On the HO side, since a HO can't pull a permit, they do their own work and it never gets inspected. For some, that's the recipie for disaster. Like I said, it's stupid.
Sounds like myself talking!! LOL That's the way it is here!!!
What you described sounds like a 3 phase panel. It's most likely a 120/208 volt type but sometimes you run into a 120/240 volt with a stinger leg. The best way to determine this is to confirm the voltage with a volt meter.
With the 120/208 volt type you will have 120 volts from each leg to ground (colored to white or ground) and 208 volts from leg to leg. With the stinger leg type one leg will read 208 volt to ground while the others legs will read 120 volts to ground. Leg to leg will read 240 volts.
The stinger leg type is not to common in new construction. You have to be careful with this type because every third breaker will read 208 volts to ground and you don't want to use this to supply 120v receptacles or equipment.
Three phase services have the advantage of bringing 50% more power by bringing only one more wire into the service. Three phase motors are simpler, more efficient, and can be made bigger than single phase motors. Therefor large AC units usually require three phase.
You can install a single pole 20 amp breaker in a three phase panel just like in a single phase panel. (assuming it is not the stinger leg). Most three phase panels have bolt in breakers meaning you will have to put a screw driver on the hot bus to loosen the bolt. Be careful, melted screwdrivers are embarrassing to explain.
LOL Tim
He might need to look at all the panels. I doubt there is just one.
120/208 and maybe a 277/480. Reading the panel label would help.
Many commercial 3 phase panel use bolt in breakers. Got to know what you are looking at to even go buy a breaker for these babbies.
Delta or Y ?
If you have to explain the differance to him, he needs to be very carefull.
Dave
Dave
You're right, it may be a 277/480 panel but the phasing colors tell me different. The volt meter will tell the truth. Other things to consider when getting a breaker is the AIC rating.
Is that stinger leg the same as a wild wire? I remember from high school shop electrical class talk about wild wire (phase) for three ph. If I remember it correct the wild wire would not have a constant voltage ,it was everchangeing.
I think I've heard it called a wild wire before. The voltage runs from 190 - 208 to ground. I've heard you can't use it for single phase either, but I'm not sure why.
"I think I've heard it called a wild wire before. The voltage runs from 190 - 208 to ground. I've heard you can't use it for single phase either, but I'm not sure why."Well you could use it for single phase if you had any of those 190 volt lamps or equipment!Frank DuVal You can never make something foolproof because fools are so ingenious.
The main advantage to 3-phase electricity is that power is constant through the cycle. For a 3-phase motor, eg, there is never a point in the 1/60th second cycle when the motor isn't able to obtain full power.
Likewise for the generator at the other end -- it's always putting out constant power (over a cycle, at least).
There are related advantages for the transmission lines.
The big motor advantages are no brushes, no commutator, no starting windings, no capacitors. You have a rotating magnetic field available, which makes things very simple and efficient.
The downside to three phase is you have more wires all over the place. So, for small applications, single phase is used. Above about 10 HP, nearly all motors are three phase.
-- J.S.
What you are looking at is a 3 phase "Y" panel. This is evident by the neutral connection. You CAN take a single pole 120V circuit off a "Y" panel. (Test first to make sure it's 120V. However, from personal experience, I highly doubt it would be a 277 or a 347 panel... not in a pizza shop)
On the other hand, a 3 phase "Delta" panel has no neutral; therefore you CANNOT get 120V from it. It is STRICTLY 208V phase to phase
3 Phase is mainly used for motors, both for constant output, and lower power consumption (at the meter) A single phase 208/220V motor of a certain size will draw more power than a 3 phase motor of the same size; because the wattage required will be spread over the 3 phases instead of just 2. And since the meter reads the higher consumption leg, the power utility gets to bill more.
BTW, isolated grounds on neon is just so that you don't get any feedback which would be dangerous for the rest of the electrical stuff
locolobo
Edmonton, Alberta, Canada
Go Oilers Go !!!
Edited 5/23/2006 11:38 pm ET by locolobo
That was an informative response. I thank you very much for taking the time to explain that to me. Not sure if this matters or not, there is a 200A Federal Pacific Stablok panel that appears to service most of the general purpose electric in the shop. Under the 200A panel is a wire box about 4ft long. The service conductors come into the wire box and then bend up into the FP 200A panel. Inside the wire box are the giant clamps they use for splicing cables, look like a block with screws that clamp down over the SE cable. off of these wire clamps comes another cable that feeds the adjacent subpanel. The panel I wanted to add the 120v SP 20A to was in the sub panel beside the 200A panel. This sub feeds a 70A 3pole breaker which appears to be energizing the buses in that panel. Those wire blocks are tapping off the main SE cable with a smaller wire to feed the FP sub panel.If at first you don't succeed, try using a hammer next time...everything needs some extra persuasion from time to time. -ME
As long as the subpanel has a neutral wire, you can get 120V. It'll be the same as the main panel. However, someone cheaped out. Most 3 phase panels these days are specced with "bolt-in" breakers. Stab-loks have a bad rep for popping loose from the bus and arcing, causing all sorts of problems. Do your customer a favor, and make sure all the breakers are seated properly before you close up any stab-lok panel.
BTW, on that "isolated ground" for the neon sign, I would take that straight back to the main grounding point, whether it's a ground rod or the water main. If at all possible, I would put it on a separate rod, but that's not usually possible in a strip mall. I would try to keep it as isolated as possible from the rest of the electrical system there, cause if something goes wrong with the sign, and it backfeeds 15KV back over the ground, I wouldn't want it to enter the main electrical system.
You see, it's not volts or amps that kills; it's volts X amps (Watts). 120V at 2 amps (240 Watts) run through the heart, kills instantly. I have seen reports of people killed by no more power than it takes to light a 60W light bulb. And then if you take that number (240) and divide it by 15,000; you will see just how little current it takes to kill at that voltage.
locolobo
Edmonton, Alberta, Canada
!! Go Oilers Go !!
"BTW, on that "isolated ground" for the neon sign, I would take that straight back to the main grounding point, whether it's a ground rod or the water main. If at all possible, I would put it on a separate rod, but that's not usually possible in a strip mall. I would try to keep it as isolated as possible from the rest of the electrical system there, cause if something goes wrong with the sign, and it backfeeds 15KV back over the ground, I wouldn't want it to enter the main electrical system."A separate ground rod would not work.For the SGFP (secondary ground fault protection), aka SCGRP (secondary circuit ground fault protection), requires a SOLID ground and a SOLID NEUTRAL.I don't know exactly what the instructions said, but from my reading it does not require an insolated ground in the common sense.http://www.franceformer.com/troubleshooting/PG-1/PG-1_primary_wiring.pdf
http://www.franceformer.com/troubleshooting/PG-1/PG-1_extended.pdf
http://www.signweb.com/index.php/channel/10/id/286/
http://www.signweb.com/index.php/channel/10/id/287/
Edited 5/24/2006 9:31 am by BillHartmann
locolobo, you said:
"You see, it's not volts or amps that kills; it's volts X amps (Watts). 120V at 2 amps (240 Watts) run through the heart, kills instantly. I have seen reports of people killed by no more power than it takes to light a 60W light bulb. And then if you take that number (240) and divide it by 15,000; you will see just how little current it takes to kill at that voltage."In a word, WRONG! It is the current that kills. A very small current through the heart muscles will deactivate them, causing heart stoppage. This is like 10 milliamps of current. WAY less than an amp! So it is the E=I/R equation that is important, where R is the resistance of the body. So a higher voltage will push a larger current through your body ensuring a killing dose of current through the heart, but a very low voltage across the heart muscle could produce the same killing current flow.If you could get 240 watts to dissipate in your heart, it would cook like a hot dog, way past heart stoppage.Frank DuVal You can never make something foolproof because fools are so ingenious.
If there is no voltage... there is no current. PERIOD!!! Current needs to be pushed! Current and volts together produce WATTS. (Basic Ohms law).
You can rev the engine all you want, if it's not in gear, you ain't going anywhere!!
locolobo
Edmonton, Alberta, Canada
Go Oilers Go
"If there is no voltage... there is no current. PERIOD!!! Current needs to be pushed! Current and volts together produce WATTS. (Basic Ohms law)."How true! If there is no voltage, there is no electrocution danger. But your statement lead people to beleive it took watts to kill. Milliwatts would be closer to truth. It is the current that upsets the biological current that makes the heart work. The fact that you can apply ohms law and get a power calculation is fine, but it is the current that kills by stopping the muscles, not the power the heart is dissipating. That would be the cooking power. Power is the ability to do work, like cooking or chemical changes.Then you could bring up average vs peak power as being important. This would be the power needed to restart the heart using a defribrillator...Average is very low, no cooking allowed. Peak is related to voltage output when they yell "clear" to force current through the heart muscles and start them beating again without cooking.And I would say maybe you have something there....Frank DuVal You can never make something foolproof because fools are so ingenious.
Milliwatts would be closer to truth.
So true... but you know how hard it is to convince people of that???
I have seen too many people; especially electricians; who tell me that "I've been shocked before, and I'm still here.... electricity is not that dangerous".
I think that what they are thinking of is all those old movies showing an "electric chair" for executing criminals, and how they claimed to do executions "only at night in order to minimize the disruption of the power grid". It takes a very big draw to dim the lights of a major metropolis. Poetic license I guess, but it gives the impression to the general public that it takes a he** of a lot of power to electrocute a man, even when he is hooked up for maximum effect.
My BIL was one of those types many years ago, until he spent 6 weeks in the hospital after being zapped while working on a 120V lighting JB in a dropped ceiling. He had a bad habit of grabbing the hot wire while splicing. This time he forgot he was laying on a heating duct which was grounded; thereby completing a circuit through his body. He doesn't do that anymore; but he also doesn't work commercial anymore. He's STRICTLY residential! (Scared the cr** out of him I guess)
I'm a commercial electrician... spent some time doing "running shoe" electrical; but I prefer commercial work, where you can take the time to do a nice job, and you HAVE to take the time to do the proper planning of the work; both for effectiveness, and for safety. He used to tease me about being scared to work "live", because I would shut off the power every chance I got. He doesn't do that anymore.
locolobo
Edmonton, Alberta, Canada
Go Oilers Go
graphs of elect.
> "I've been shocked before, and I'm still here....
Well, duh. Of course it's only the survivors doing the talking.
The other important factor is where the current path is in the body. If it's between the thumb and fingers of one hand, that's less likely to affect the heart than if it's from one hand to the other.
-- J.S.
"ANY electrical shock has the potential to cause injury to humans...doesn't matter if it's 120 volts AC ...or even 12 volts DC...both can cause injury or even fatalities.
(for example, lightning is DC...and it kills hundreds of people every year...as does regular 120 volt household AC) The amount and kind of injury depends on six things - voltage, amperage, resistance, type of current, path of current, and duration of exposure. It has been found that as little as 20 milliamps can be fatal...especially if the duration is fairly long. Anything above 60 milliamps can be quickly fatal...just a few seconds. 5 milliamps is the point at which we definitely feel the shock current...enough to definitely get your attention - but you can let go of a live wire with 5 milliamps of current on it and it is rarely fatal. In the 5 to 20 milliamps range - you begin to no longer be able to control your muscles...and often can't let go of the live wire....and if enough time passes (before the power is shut off or someone knocks you clear) - this shock CAN do extensive damage...and CAN be fatal. 20 - 60 milliamps can be fatal within a few seconds...it can cause fibrillation (where the heart pumps little to no blood)...and can completely stop the heart.This is why CPR training has become a requirement for most electricians...(it should be for ALL)....to possibly revive someone's heart who has been shcoked. Anything from 60 milliamps on up is generally considered fatal...and will stop the heart of even the most healthy people...in under 3 seconds. "http://experts.about.com/q/Electrical-Wiring-Home-1734/dangerous-amperage.htm
"On the other hand, a 3 phase "Delta" panel has no neutral; therefore you CANNOT get 120V from it. It is STRICTLY 208V phase to phase"Unless one of the 240 transformers is center tapped it is the neutral. Then you have two 120 volt legs and a high leg."3 Phase is mainly used for motors, both for constant output, and lower power consumption (at the meter) A single phase 208/220V motor of a certain size will draw more power than a 3 phase motor of the same size; because the wattage required will be spread over the 3 phases instead of just 2. And since the meter reads the higher consumption leg, the power utility gets to bill more."Power consumption of 3 phase motor is not significantly more than singel phase.And the power meter measure the POWER on each phase and TOTALS it. Not the power on one phase and tripples it.
> Unless one of the 240 transformers is center tapped it is the neutral. Then you have two 120 volt legs and a high leg.
Is that very common? I've run into it once here in LA, and that was on a very old hotel building, probably pre-1920's. Big thick slate boards with brass and copper bars bolted thru them, big open knife switches, beautiful antique stuff.....
-- J.S.
The Australian electrical system is different to yours but if you don't know anything about 3 phrase do not touch a mistake can be fatal and as another post said if you are not an electrician you should not be doing this anyway you would void the pizza shop owners insurance for an illegal electrical connection In this country all electrical work must be carried out by a licensed electrician only
Edited 5/25/2006 11:33 pm ET by Bolts
Edited 5/25/2006 11:34 pm ET by Bolts