110 V Phase Questions

They are 180 degrees out of phase. You are supplied with a center tapped secondary with the center tap connected to the neutral.

I question the wisdom of connecting transformers in parallel. If the voltage and phase of parallel transformers are not identical, you will get circulating current.

They are working now that I have used a common power wire for all 3 pairs. I think it was that circulating current that caused the third pair to turn the tape a bit dark in the center.

I am using them in parallel because I was getting the voltage to drop from 27 V to 21 V when the motors cycled. Now with 3 pairs it only drops to 23 V.

So if 2 phases are 180° out of phase how do you get 3 phase 120° apart? I read something about the center tap but don't understand it.

Drew K

Neutral is center tap, line 1 and line 2 are 120 volts from neutral and 180 degrees phase difference (opposite phase).

http://electrical-engineering-portal.com/single-phase-power-vs-three-phase-power

You should have found 208V between phases 110*√3.

You electrician should have known not to put two phases on a test bench.

I can't say I'm too impressed with two separate feeds to the same bank of sockets. Is there a means to isolate both feeds simultaneously?

My test bench is a set of shelves that we put motors on for cycle testing. The plant maint guy wired up a quad plug socket using a pair of double sockets. He said he put them on different breakers so if we tripped one we would still have power on the other...I guess he anticipated me letting the smoke out of some equipment :-/

I have another test bench for locked rotor where I can control the voltage and frequency with a big digital power supply.

Drew K

OK what I'm alluding to is the safety of your workstation. A fault should kill all supplies, clearly it won't as it stands now.

Test benches for electrical equipment separate feeds isn't a good idea, separate phases even worse.

You really need to get your electrician to buck his ideas up.

I don't disagree with you at all. But here I am only a small cog and they have always done it this way. They are lucky that everyone who works in the area has real world experience with making things work in a substandard situation.

Any inspector in Europe would shut this down, I bet even OSHA would have stern words but they say nobody has been hurt and I know what I am doing so why fix what isn't broke. If I stay here long enough I might try to get it all up to spec but first I need to feed the family and validate the product.

Drew K

I don't know what world you live in. But I have bills to pay. If I make demands like that I will be looking for another job; they will get someone else to do it. I know if that happened I could get unemployment or sue, but you have to have money to sue and unemployment doesn't pay what actually working does. With devalued currency, inflating costs and a flatline for income I am drowning anyway.

Drew K

It was stated as should not must. What you do is your own prerogative. Please note the cross out.

Is your life worth the high probability that someone, especially you, could suffer a fatal electrocution? Speak with them in a respectful manner and they will probably want it fixed as much as you do.

Also the anonymous calls or filer not revealed complaints are always available to you. They are most often successful. It is usually the complainant with "loose lips" that reveals who filed the complaint that causes them to be known, not OSHA. Almost every time in my career that OSHA knocked on the door with an anonymous complaint I found out who filed it by that person having loose lips. Many people like to brag about such things.

Good Luck, Old Salt

Unless they run separate neutrals. -- JHF

Wrong. Using 2 different circuits as the electrician did is the most common way it is done. What you have if you parallel the 2 receptacles is 208 volts. The transformers are rated at 110 volts. That is the problem.

I have to agree with Andy, that it is in all likelihood a single phase feed to the mains transformer primary, with a split phase (central tap ground, neutral) live as 110V on either end from the center tap, and one end is 180 degrees out of phase with the other end, the way I see it.

The operator is taking both these 110 V feeds to two different transformer primaries, then tying them back into parallel, and letting the smoke out of the transformers. No brain element required.

Best thing the operator can do is run both these down stream transformers from the same tap of the mains transformer for the "A" motor test (in parallel and in phase to get more current), and set up a separate test transformer circuit for motor testing as "B" that is on the alternate tap of the mains transformer.

He probably has 3 phase power like he stated.

Two (2) phase power is not used any more. It was replaced with 3 phase power.

Additionally, it is 120 deg out of phase.

We do have 3 phase but I have not looked to see if it is in that panel or not. This bldg used to mold plastics. The motors I test are fractional hp shaded pole. They don't pull many amps but this is the first 24 V test that I have done and had a hard time getting enough power to keep the voltage from dropping too low when the motors cycled.

My mistake was running multiple plugs to power the transformers, I wound up using 2 different legs. The spark that it made when I was testing it was not as big as when I have seen 120 V grounded so I don't think it was 180° out.

I am just trying to get a better understanding of how it all works.

Drew K

It is three phase, read the OP.
119V to neutral, 119*√3= 206.11V. Near 208V as I first said.

The OP also mentions running 240V 3Ph motors on the bench. If he's doing load tests the lower voltage could give interesting results. IE not very accurate results.

You need to read the OP correctly. Not one thing you have said here matches what the OP said.

If his 120 volt source is derived from a 208/120Y source,you are correct.

There are plenty of industries where,in addition to 208/120 Y they have single phase 240/120 Volt single phase.

I have worked in an industries that had 600V 3phase,240 3 phase,even 120v 3phase,and 3 phase derived from only 2 transformers on a 3 phase supply(a sneaky way to get by temporarily when one transformer goes bad).

As previously stated,240/120 is derived from a center tap of a single phase transformer.

Some refer to it as 2 phase,but this is a misnomer.

Residences in the USA are provided with 240/120 single phase,with center tap as neutral,which is also Grounded(not to be confused with Grounding).

The NEC is funny like that,and the terminology is sometimes confusing to the apprentice.

I know very little about the European wiring codes,so you can probably teach me a lot.

<Ahem>

One may assume that the original poster is in the United States, from the tag line though it is not explicitly stated. It is commonplace there to supply split-phase, particularly to domestic installations, where the two phases are 180deg out of phase. In such a case the phase-to-phase voltage would be 110V*2 and not 110V*√3, as would be the case in a three-phase situation.

</Ahem>

In the United States the normal electricity supply to "lower power users" such as described by the OP and residences is 240V with a neutral located in the center of these "hot legs". Since the actual supply is one 240v supply it is single phase since only one phase is supplied. With the neutral on the center-tap of the 240v the source of the 120v is (120v, hot #1 <-----> neutral <---> 120v, hot #2) and 240v is (hot#1 <---> hot #2). The 120v source, with the two legs derived by going from neutral to each hot leg, #1 and #2, is often misstated as 2 phases when it is really single phase. Supply voltage is measured from hot leg to hot leg, not hot leg to neutral. The supply is therefore single phase since there is no other source of power.

2-phase is seldom used. Currently the only location that it is used is center city in Philadelphia, PA, USA. Most of the power there is 3-phase, before further segmenting to single phase. 2-phase is generated by two separate and independent windings located physically 90^o apart from each other. This system requires 4 wires to supply with, two for each separate and independent leg. See https://en.wikipedia.org/wiki/Two-phase_electric_power for illustrations. The original configuration for the Niagara Falls hydroelectric generating plant was 2-phase but changed to 3-phase after it was determined that it would be less expensive for distribution wiring, 3 wires instead of 4, and the generating equipment would be less expensive.

3-phase is usually generated by three separate windings in the generator and these located 120o apart from each other. Outside of this unit the windings wires are connected so that each winding is connected to the next one. It is called "3-phase" since there are 3 windings, each with a 120^o difference in potential to the others at any particular instant. For further clarification see https://en.wikipedia.org/wiki/Three-phase_electric_power and http://www.oempanels.com/what-does-single-and-three-phase-power-mean

The example the OP has described is single phase. Unless he is located in parts of center city Philadelphia, it is not 2-phase. 3-phase requires more wires than he has.

The power in question is 1-phase (single phase).

Good Luck, Old Salt

There are a good many other places in the US that distribute 2 phase electricity other than Philadelphia. South central Wis for instance.

What do you describe as "2-phase"? It is extremely expensive as compared to 3-phase both in generation, controls, distribution (4 vs 3 wires), cost of unique equipment to use it.

See- http://electronics.stackexchange.com/questions/73177/difference-between-single-double-and-three-phase

I would STRONGLY suggest that your comment be researched further before it is withdrawn.

Good Luck, Old Salt

LOL.

Well put!!

You are very right. It's a rural area and not an REA. It's a private supplier who owns that area (franchise?). Good luck getting any change. It's been a few decades now, but I haven't heard of any change since I left.

For all the 2-phase'r out there-------> a quote from Continental Control Systems, LLC., a manufacturer of AC power (Kilowatt, KW) and energy (Kilowatt hour, KWh) meters. Hopefully this will clarify my comments in previous postings on the subject.

http://www.ccontrolsys.com/w/Two_Phase_Electrical_Service

What is two-phase electrical service?

Residential electric service in the United States (120/240 VAC) is sometimes called two-phase service but this is NOT correct. It is only single-phase, since both line voltages are derived from a single phase of a distribution transformer with a center tapped neutral and are 180° out of phase with each other.

Two-phase service is an obsolete style of electrical power distribution where two phases are provided that are 90° out of phase with each other. There were two line wires and one neutral, so two-phase service was commonly a two-phase three-wire service.

Another variation used four line wires and one neutral for a two-phase five-wire service. This was sometimes incorrectly called four-phase five-wire service.

We are not aware of any two-phase service still in use. However, the WattNode should have no trouble monitoring a two-phase three-wire service.

I hope this explains the two phase system and provides further clarification to any contributor who might not understand this concept completely.

Also go to the following sites. It is well worth the efforts.

https://answers.yahoo.com/question/index?qid=20090809202958AAKJkjf

http://www.ccontrolsys.com/w/Electrical_Service_Types_and_Voltages

http://federalpacific.com/training/transformer-basics/chapter-6.htm

http://www.ashireporter.org/HomeInspection/Articles/Let-s-Talk-Three-Phase/2358

http://www.allaboutcircuits.com/textbook/alternating-current/chpt-10/three-phase-power-systems/

These all have at least something for everyone, from the beginner to the highly skilled expert EE, to learn about.

Can you provide locations and/or web sites for that?

You said...

Important: This is not a NEC violation and the breakers are not required to be "ganged" because there are different devices normally attached to each breaker.

Yes... I agree fully, this is not a NEC or CEC violation. You could have 10 duplex receptacles fed from 10 three wire branch circuits in the same box and be fully code compliant.

Both the NEC and the CEC require that the feeds to a single device (one of the 10 duplex receptacles I mentioned above) be tied together and not that all of the disconnecting means for the devices in a box be tied together.

You also said...

His mistake was in connecting the transformers in the wrong configuration thereby placing/applying 220V across the 110V rated primary winding.

I think his issue was on the secondary when he paralled the transformer windings and not on the primary. There was no way he got 220V or 208V across any of the primaries.

I am not sure exactly what happened but:

"I wired in another pair of transformers but this time I plugged it into the other side of the outlets and almost burned up my transformer!"

I would surmise that as long as the transformer primaries are fed from the same voltage phase source then Lenz Law would apply.

Therefore reversing the secondary connections polarities from transformer to transformer in any combination would result in a "Buck" or "Boost" effect or a combination of both to the secondary output voltage but would not result in a fault.

I believe, after reading all the posts by the OP, that your explanations to be incorrect!

What I believe is that he intended to do was to parallel two or more transformers between a 120 VAC live side and neutral. He considered/believed that the live sides to be the same "ends" of the same phase, but the were in fact opposite ends of the same phase....

I do agree that the data we have been given has been given a) very slowly b) is still incomplete, but I do not draw the same conclusions as you have.....not yet at any rate!!

I was careful not to put more than 110 V to each transformer because I ran one plug to each pair of transformers. I tested the ouput voltage from each pair before tying them into the relay. I was surprised when I heard the buzzing of angry windings when I plugged everything back in after tying in the last pair of transformers.

I quickly pulled all 3 plugs and had a friend hold the multi meter as we plugged back in. I don't recall the output voltage drop as the other phase was activated but it wasn't significant enough for me to think I had reversed polarity which was my initial thought when the windings vibrated.

This was when I got the maint guy who explained that the 2 pairs of outlets could be on different legs. He is old school and has been working here for decades but is an all-around maint guy, I don't know his credentials.

Watching the output voltage drop when the motors cycled I was pretty sure I would need to add more transformers in parallel to distribute the load. They were rated at 4 amps and I know I wasn't getting near that but the drop was to 21.5V and I could hear the motors were not sounding as robust as normal. Now with 3 pairs of transformers my volts are only dropping to 23 V. So far I have not had any failures and am at 200k out of 250k cycles.

Drew K

If you had one single phase 110V transformer plugged into an outlet that was fed from a breaker in a distribution panel and then you plugged the second or third transformer pair into an outlet fed from a different breaker in the same panel the transformer output voltage waveforms will be at least 120 degrees out-of-phase and could be as much as 180 degrees out-of-phase.

This phenomenon is due to Lenz Law which basically states that the AC voltage waveform induced by a transformer's primary winding into the same transformer's secondary winding is 180 degrees opposite in polarity in reference to the applied primary voltage AC waveform.

If the secondary windings of the transformers were in parallel this scenario would cause the transformer output voltages to be opposite in polarity for every AC cycle allowing maximum difference in potential between the secondary connections.

This would mean the condition presented to the transformer secondary winding(s) circuit was pretty much the same as applying a direct short between the transformer secondary winding connections.

When connecting multiple single phase transformers in parallel to increase VA capacity it is extremely important that the primary and secondary windings on all transformers are kept of the same polarity and in-phase. (Primary-to-Primary and Secondary-to-Secondary)

In order for the output voltage and current of each transformer to be additive both of the following conditions must be true:

1) The instantaneous direction of current through all primary windings must be exactly the same in reference to time. (In phase.)

2) The instantaneous direction of current through all secondary transformer windings must be exactly the same in reference to time. (In phase.)

If you Wiki or Google "phasor diagram", you can find out more about how this works geometrically.

I will not open this can of worms yet once more. OP... if you are interested in my opinion on this send a PM please.

In any event you might want to consider swapping the circuit breakers in the panel so that both outlets are on the same leg.

You being someone who knows how to properly handle this dangerous 30 second operation without load balance or electrocution issues. (don't forget to re-label the door!)

If it doesn't have gears or come out of a hose, I don't touch it.

You can touch it...just don't touch a ground at the same time!

Drew K

Don't try this while sitting on a recently damp stone railing. It may shock your cans, butt what would I know?

If you try this while standing. Perch on one leg so you have a better chance of falling over and breaking the circuit in the event you electrocute yourself.

If you try this in chicago where we use conduit and steel boxes it becomes a lot like the game 'Operation', but more exciting.

...on second thought. don't do any of this.

None of this has ever been done before because it's not safe and it's always easy to find whatever circuit you are working on. ... Really

If you want to avoid being shocked then just make sure you touch it when the AC sine wave is exactly at the "zero" point.

180° Opposed is one way of looking at it, but really a 110VAC circuit is simply "half" of the same 220VAC phase coming into the building, with a central neutral, which is also grounded at some point!!

Basically you shorted out both ends of the same phase together I believe, not good!!

I personally would never place transformers in parallel anyway, but thats just me.....I would have bought an oversize transformer in the first place, (I always do!).

You could get a special plug/socket for US 220VAC installed as well and feed the 220VAC motors with 220VAC directly.

With regard to the 24V (AC?) Motors, you need to check the power needed to run them and the "size" of the transformer(s) you are using. Something is not kosher.....but not enough info to give a correct answer....

Don't forget that induction motors generally take a large surge of current at startup, usually around 6 x running current, but could be even more!, unless they are Universal, or specially designed not to.....

Don't forget to earth the motor frame and I do recommend a RCD or the local equivalent in circuit for safety reasons.....for all sockets of course!!

As for the installation plugged into the sockets, would it be fair to say that the services of a qualified Electrician are overdue, perhaps?

As you guess, you have a 2ph supply, but gardless of the precise voltage and phase angle, this sort of wiring arrangement is not allowed - it is dangerous as you have found out - even back back in my apprentice days in the 50's it was frowned upon.

I'm out of touch having retired 15 years, but UK regulations and standards no doubt ban it nowadays - or require absolutely clear labelling and complete safety protection if 2 or 3ph power is required.

I will leave today's experts to quote chapter and verse.

Its actually a 1 phase system (which many, in the USA as well, wrongly believe is a 2 phase system!), center tapped for neutral and also center earthed somewhere.

But it should feed with 3 wires to 3 pin sockets nowadays....I am told!

Thats a modern standard US installation, except that the electrician ran both live phase legs next to each other to separate sockets, which if I understand the US Citizens here, is maybe at the very least, very questionable!!

Especially when one realises that he managed, to short both phases to each other, not having the equipment or the knowledge to compare the phasing,or to check if they were the same or not!!

It was also not mentioned (I believe!) as to whether the sockets were 2 pin or 3 pin. But if I remember correctly all new installs must be 3 pin in the USA.

But as to if the OP used 2 or 3 pin plugs for his (to my mind) more than slightly dangerous experiments, was also not noted....

No RCD or local equivalent was mentioned either.....only current overload breakers are installed....which is simply not good enough to my mind.....

Disregard the website, but the image at the top of the page is what I see on the wall. #1 and #3 are on the same leg but #2 and #4 are on a different. My thoughts from a home-made extension cord that terminated in on of these boxes was that all the hot' wires were common so it wouldn't matter on the transformer that I used different sockets.

Turns out because they are on different legs there must be a phase difference because the windings started heating up. My original question was related to why they heated up. Based upon what I thought I knew about wiring I thought I had an inkling as to the problem. Presently my thoughts are that the 2 legs are part of a 3 phase box and are 120° out.

This is not my ideal job, but it is better than what I have had for the previous year and I am just trying to do my best with what I have. It is too small for any reports to be anonymous so I am keeping my mouth shut to keep working.

Drew K

Exactly correct. GA

I do not see it that way at all according to the OP.

If you check the good diagrams from the Old Salt, you will see that he has ONE PHASE, centrally tapped and grounded for neutral and ground.

Some sockets are fed from one phase arm A and neutral, the others are fed from the other hot phase arm B and neutral.....but its the same phase winding, just both ends, one labelled A and the other B....

A typical system used in the USA for man years now and discussed here on CR4 many, many times....

There was a mighty big word in my post: IF. You are correct that my IF statement was false, then the rest of the single phase argument follows. My apologies for any misleading confusion I may have generated.

Yes, the separate taps of a single phase transformer with central neutral tap are indeed 180 degrees out of phase, by definition. Any combination of transformers downstream of these taps must not be connected in any series-parallel combination without drastic over potential, over current issues in each transformer in the arrangement.

To put it bluntly: hey morons, you let the smoke out of it again!

Hey! I was ignorant not moronic! And I did catch it before most of the smoke got out...just a little escaped before the buzzing windings caught my attention.

My solution was as your other post suggested that I use one common power wire instead of using separate power wires.

Drew K

Sorry about the moron comment, too much coffee this cold and airish morning! Morons have one way of doing things, that is apparently involving hammers and electricity, whilst the ignorant have many ways of doing things, most of which they invent on the fly.

Ignorant is me then! When I see sparks or smoke, I know it is time to learn something new. No need to apologize, I knew where you were going with it : )

Drew K

No they are not 120° apart. They are the hot legs from the SAME PHASE, therefore they are seen as being 180° apart. Just opposite ends of the SAME phase....

I would have thought that 7 or 8 people telling you that here, it might have sunk in!!

This is ONE of the three phases generated, ONLY ONE!

Got it now?

I think you are the first one to explain opposite ends of the same phase. That makes sense.

Without a scope, is there a way to tell for sure? The box feeding the breaker panel is a "HEVI-DUTY" general purpose transformer Catalog No. t2h30s 270lb 30KVA 3 phase 60 Htz 150 C rise H.V. 480 Delta L.V. 208y / 120.

Drew K

In the OP, you said 220/110, which strongly implies single phase w/ center tap neutral.
Now you say 208/120, which definitely entails three phase w/ neutral.
One set of voltage measurements must have been off.

I had never measured the "220" volt outlet until this morning. It reads 208, and when I read across the 2 sides of the 4 way I get 208 also. Now I have to bring it up in the next meeting to make sure everyone knows I am testing the 220 V motors at 208. It is a lifecycle test and my failures generally come from the gearbox so I don't think it will be that critical. The constant cycling is the way they have always done accelerated aging to simulate years of service and is fairly harsh when compared to actual operations.

Drew K

Are you monitoring many variables? Did you know that you can set up Arduino boards that will push data directly to an Excel spreadsheet? There are 3-wire temperature probes that are digital, and many of these can be connected to one hub on the Arduino board. Not only that, you can set up 16 bit A/D converters with these boards, and have many inputs. You can get a $29 data-logger starter kit from DATAQ (DI-145)that will allow you to record 4 inputs on your laptop (even in Windows 10) that will effectively provide you with an oscilloscope for watching the phase of your various motor inputs.

I am surprised that you are not burning out motor coils, since you are supplying them under potential. If the gearboxes are the weak link, then so be it. I hope stray current into the gearboxes is not the issue here.

Good luck, hope I at least marginally provided you with some Merry Christmas ideas.

I want to get into an arduino kit to monitor operation. I need to learn the programming language. Right now I have a relay set up with a timer to cycle them on and off. I check on it in the morning and don't know how many cycles went on overnight before a unit failed. I want to set up an optical sensor to detect when the unit operates and count operations until failure and dump the data in a spreadsheet for me.

Now if only I can get caught up on the pile of test reports needing completion and the inbox full of tests to start I will learn programming!

Drew K

You sound like you will have to work some at home learning the programming, but fortunately (I really do not know much on this) there are many, many open source examples. Relay control is fairly easy, even I can do that one. Counts should not be that hard. Data inputs may be a little bit more demanding.

Good luck.

Running at a lower than "planned" voltage is a hard test for any induction motor, they will usually run hot if fairly well loaded....a hard test.

If you need exactly 220 VAC, then some form of transformer may be a requirement, maybe an "Autotransformer" if the load can be handled (I don't remember what current your motors require, sorry!), that way you can turn the voltage up!!

As a side note- It would be easy to become confused between a 220v and a 208v meter reading, especially while under load. Perhaps even with no load.

Hypothetically, if the panel box (assuming not losses into there) were located 200ft away from the outlet box, the supply voltage from the panel is 220v, #12 single phase wire from the panel box, a 20amp load, then the resistance of the wire would cause the voltage at the outlet box to be an actual 13 volts less. 220v -13v line loss = 207v actual at the outlet box. If this is the only measurement and analysis done the circuit would to appear to be one winding of a 3-phase supply.

In measuring the voltage, the error of the meter must also be considered. If the quality of the meter is at a minimal level, a 3% error would cause another 7 volts misreading loss. 207V - 7v (3% error) = 200v. Even with no load on the circuit the voltage read at the sockets would be 220v - 7v meter error or 213v. This is also close enough to be misread if a analog meter is used. Digital errors are slightly less than analogs.

As you stated- Which one is it? 220v, single phase or 208v, one leg of a three phase? It is only 12 volts or 6% apart

Good Luck, Old Salt

Voltage drop will only effect a voltage reading if the reading was taken while the circuit was under a load. No load... no voltage drop.

Please refer to 3rd paragraph, 4th sentence-- "Even with no load on the circuit the voltage read at the sockets would be 220v - 7v meter error or 213v." A circuit with no load but with voltage applied to it would read less than the actual voltage (or greater than) due to the meter error. Meter error does not have to have a load on the circuit to be present unless the meter is measuring current, such as a clamp-on meter. If an analog meter is used there might be a current draw on the circuit of 50 microamps to 1 milliamp depending upon the internal resistance of the meter. With a digital meter the current draw would be infinitesimal.

Only a meter standardized to a NIST reference or the first generation from it could be trusted to make an extremely accurate reading. For almost every meter in common use there would be an incorrect reading of the voltage drop/voltage gain for this situation. Depending on the design of the meter and the use/abuse of it this could be as high as 5-6% or higher and as low as zero at any specific time.

No load...yes, a voltage drop may be read! Please refer to #60 for further explanation and clarification.

Good Luck, Old Salt

You asked:- Without a scope, is there a way to tell for sure?

Your question is really good, but I am unaware of anything the does that, BUT, the people here will know if such a tool exists.....

BUT!! If I understood another poster here properly, US Code forbids it!! With good reason I feel!! Therefore the electrician should correct to code.

This is what Old Salt mentions in post #19. I believe he knows what he is talking about.

If you make an official complaint, and its not corrected, your company will be liable.....you may even save a person from an as yet, not happened accident!! I remember your worries about your job, but what is more important....?

Even if it is allowed, there could be some simple markings that could be placed on each socket to show what phase and what leg for example.

In the RN, all supply boxes were marked with a simple code that was easy to decode and find out such things.

Though we did not have the neutral point passed out from the 3 phase 440 Volt 60Hz NATO ship's power.

All domestic supplies of 230 and 115 were made using heavy local Delta/Wye transformers where needed from the 440 Volts mains, dotted around the ship....lighting was the main usage.

"BUT!! If I understood another poster here properly, US Code forbids it!!"

No, the code in the US does not forbid such arraignment.

The code DOES FORBID IT.

Please provide further information/proof that the 2014 edition of NFPA 70, the National Electric Code (NEC) does not forbid it. Please support your unsubstantiated statement.

If available, please cite the source of the statement. Andy Germany likes that and it is appropriate in this case.

Please provided the section and subsection of the code where it is stated.

Good Luck, Old Salt

Ok. This is what I came up with.

Chapter 1 Article 100:Branch Circuit multi-wire

Art. 210.7

Munster-

In reference to your #64:

NFPA 70 (NEC), chapter 2, Wiring and Protection, art. 210.4(B)-- Disconnecting Means. Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates. Plain English--- All the separate circuits in a box shall have "tie-bar" breakers, breakers configured so that one handle controls all the breakers handles simultaneously, for each ungrounded (hot wire) conductor in the subject box.

210.7 states the same thing, it forbids it. When two or more branch circuits supply devices or equipment on the same yoke or mounting strap, a means of simultaneously disconnecting the ungrounded conductors supplying these devices shall be provided at the point at which the branch circuits originate.

Also, the NFPA 70 (NEC) is accepted by all 50 states as their standard, including New Hampshire.

Good Luck, Old Salt

Like it!!

GA

And the code in Canada does not forbid it either.

What the Canadian code does require is that each piece of utilization equipment (such as a receptacle) must be equipped with or fed from a control device that disconnects all sources of voltage.

There are exceptions to this requirement... for example, for multi wire branch circuits feeding lighting loads or non-split receptacles, such provisions are not required.

North of 60-

Previous postings by the OP and comments made in this blog strongly, if not positively, indicated that he/she/it the OP is located in the USA and is interested in information concerning the situation he has here in the rebellious states.

If the code in Canada does not forbid it, the inclusion of "either" in the sentence would not be correct since it is forbidden in the rebellious United States. The NFPA 70, National Electric Code, is accepted as the applicable standard in all the 50 states of the United States.

Can't help you with Canada. I'm a born and raised proud American. Sam is my Uncle and Smokey is our pet.

Good Luck, Old Salt

LOL!!!

That what I understood from Old Salt.....and it would make "safe" sense....

"Arraignment" is a legal proceeding, having nothing to do with "arrangement".

Now you tell us the transformer is 3 PH. Is the transformer actually connected as designed, with all three phases correctly active? If so, then to run a single phase, you effectively are using 2 of three taps of the star or delta, or using one tap to neutral. You still have but one winding on the primary and one winding on the secondary of your 1 PH mains transformer, again, one central tap, with two output taps. The two output taps are still 180 degrees out of phase by definition (disregard my previous drivel in other post).

Here, let's stand all of this on its head: Here is how you run a 3 PH motor off a 1 PH supply (be careful about the voltage ratings and the supply, and make sure to use enough capacitance on the shifted lead).

single phase supply runs a three phase motor with serious caveats

So if you watch both segments of that video, you will learn something.

Now suppose you want to correct your situation in your lab, Mr. Drew K.

Perhaps the clever way (consult with your electrical geni locally), might be to phase shift the half of the outlet box on the B tap of the mains single phase transformer, but you either need a small synchronous condenser for that, or a sufficiently large capacitor bank (most likely switchable) to make both of your parallel motor supply transformers operate in parallel and IN PHASE. Problem more or less solved, but can be dangerous if 1) you lack the in-house expertise to come up with the correct capacitance value(s) at the correct voltage rating, or 2) a capacitor fails under the load testing of your motors.

Disclaimer: I am neither an electrical engineer or an electrician. I suspect that my suggestion is not allowed in NEC practice. Do not use this, unless you are simply experimenting with it in a controlled situation, and have back-up standing by to kill all power nearby.

I cannot wait to get the vociferous feedback this post will warrant.

Hello Andy - post #24 is me - Horace40 - from what you say in your reply to #24 it seems to me that you had some other post in mind when you wrote it - apart from whether it is 1ph or 2ph - I can't relate what you say to anything I said.

Hi, how are you keeping?

You wrote:-

As you guess, you have a 2ph supply, but gardless of the precise voltage and phase angle, this sort of wiring arrangement is not allowed - it is dangerous as you have found out - even back back in my apprentice days in the 50's it was frowned upon.

It could not be dangerous as it doesn't exist anywhere in any office/domestic situation, but even if it was, it was many years ago, it fell out of use mainly due to the higher transmission costs I believe.

Old Salt has mentioned this several times and supplied some good links, so I have no need to rehash it again. Simply forget it....

There is one place in the USA I believe where it is still in use, but totally industrial...

Best of luck.

Two phases can still be used for sockets in the same room/area. The requirement to identify such sockets has been removed from the 17^th edition along with some of the plethora of labels.

Pointless sticky labels, the bain of my life!

I do not agree personally with anyone saying "Two phases", unless you actually mean two of the three 220 VAC phases of the output of an alternator, which surely seldom happens in either the USA or the UK in domestic situations. Like never?

They both get a single 240 VAC phase coming into the house. UK 50 Hz, US 60 Hz. The UK does not centrally tap the phase for neutral though!! They simply use one of the "sides of the phase and connect it to ground at a single, planned point and label it as neutral! Simple!!

When I see or hear someone mentioning "Two phases" in the USA for example, it demonstrates that that person simply does not understand technically the US domestic mains electricity, which could even create danger for others, less well informed....

1, 2 or even 3 phases can possibly appear in a single room here in Germany fully legally as each house gets 3 x 240 VAC phases as standard.

I actually fed 3 phase into my kitchen when I revised it in 2008, to allow major "cooking days" without popping a breaker......!! Which we never ever have since!! There are 27 x 240 VAC sockets in our kitchen!!) Also each phase has an RCD as well for extra safety, for the whole house.

The words "Two phases" (as I believe you meant, but correct me if I am wrong!) are often incorrectly used/misunderstood to describe the 240/120 VAC in US domestic systems where "ONE PHASE", is "SPLIT" into 2 x 120 VAC for domestic usage by center tapping for neutral. THAT IS NOT 2 PHASES!!

It is still only one phase!!

The correct name appears possibly to be "three wire, split phase, 240 Volt System". That describes it well I feel.

Which you can read more about in this link:-

Mains_electricity

Fully reading this CR4 blog as well (and several others over the years on CR4), would have cleared that up fully!!

So why should I believe someone that says it is allowed, who posts no covering link and calls one phase two phases? Which is Patently wrong!!! So sorry, but I do not believe or trust you.....

You may even be right and it IS allowed in the USA to have two sockets on different legs of the same phase near to each other.....! I am not saying it isn't....

But I would rather believe someone like Old Salt and his posts here on this blog, until proved otherwise. He posted not only some SENSIBLY formulated knowledge, but also some links supporting all his comments, as do all the "professionals" here....and I do believe he NEVER calls it "Two phases"!!

THAT'S THE WAY TO DO IT!

Posting "throw away" comments with no proof of validity, is just a waste of your time and it does not improve your image here either......

Not that having an "IMAGE" should be that important (though some here think differently!), but 100% accuracy and fully correct infos should ALWAYS be our aim.

For me personally, if I lived in the USA and an electrician I wanted to use started talking about "Two Phases", he would not get any work to do for me, he would simply be shown the front door and how to use that.....I would rather do the work myself, in spite of my bad back!!

I hope this post stops once and for all time the words "two phases", when it is not!!

Rant over!!!!

You going to have problems with semantics and syntax here especially with us old-school electricians.

I started out in the world of electricians in the UK in 1951 and everybody I knew would have described the OP installation as having 2 phases and they would know and understand perfectly what they were talking about - and would not have allowed the OP's dangerous situation to arise.

The fact that this OP might have 1-phase or split-phase or any other name to describe it, is a technical point that has only emerged from the threads as discussion progressed.

I wish you well with your campaign.

Does anyone have a can of exclamation mark suppressant?

To TonyS #73

Are you saying that 1-ph sockets fed by two phases in the same room can now be adjacent/together ? - without warning labels?

I can't quote the actual clause (of any edition of the IEE Regs way back) but I vaguely recall sockets were not to be less than 6ft apart if fed by 2 phases - the logic being far enough apart not to be reached by outstretched arms to stop you poking your fingers in the live holes.

This thread has become a basket case of incorrect "information", almost to the point where the whole thing should be zapped as spam.