208V 2 hots edison tap

[wippin' boy]

I say the op was parroting something from someone who was looking at a panel running off a step down transformer in a 480 3phase shop.
panel was as described by many
208 three phase with a neutral for single phase.
the goof heard "Edison three wire" once in high school and was tickled pink he got to say something close to it after all these years.

motor data plate info required Mr op

 

[3t3d]

Maybe I am reading it wrong but it still sounds like 240 with the center tap as neutral. The two 120 circuits share a common neutral. On the output of a delta wye transformer, three 120 volt circuits share a common neutral. The term Edison circuit is just not in common use.

Sent from my SM-G900V using Tapatalk

Typically if you are running wires for outlets, you need a separate power and neutral for each circuit.
If you have two 20 amp circuits, you need two 12 gauge wires for the power, and two 12 gauge wires for the neutrals, and 12 gauge for the safety ground.

All the circuits should have their own separate neutral wires of the same gauge.

Only in the special case of the Edison Circuit can you eliminate one of the neutral wires in the wiring run.

Just a special case to reduce the number of neutral wires.

 

[dgfoster]

That is correct.



Except for virtually all commercial offices, residential towers, larger residential complexes, condos etc. etc. etc.

The POCO sure as hell ain't gonna install both, 3PH-Wye AND single phase 240 service.
For an almost guaranteed test, just sneak into your local hospital or medical center and plug your meter into any of the single phase outlets.
You will find a proper 208V reading.

Now as to what an "Edison" tap is?

OK, not film processor: http://www.medicaldevicedepot.com/S...wEteqiUg8D4RFMISTOSaJ95t5hF0wDmfBFBoCe_7w_wcB

Yes, it CAN use 120V, but in most hospitals they were plugged into dedicated charging outlets, which were 240 single phase.

Another: Buy SonoScape - A6 Portable B/W Ultrasound Machine -online

Granted, I am now 12 years removed from the medical field, but back then Ultrasound units weighed #2000 and then some, and each and every one ran on 208/240 single phase.
And, being "portable" units, most of the rooms had at least one single phase outlet in them just to accommodate bedside diagnosis.

Well, you have gone from saying all single phase units in all hospitals give a Proper 208 reading which is complete hogwash. Then you show a couple of dual voltage devices which could be plugged into a 220 circuit b ut which are also wired for 110----and for good reason; they are simply charged on 110 circuits. Even true for portable xray units, the largest power users of the portable diagnostic equipment, which were not plugged into power outlets in the roomat all, but instead were kept in a state of adequate battery charge, so they rolled into a room and just made the image on battery power. When not in use, they resided in the hallway plugged into, yup, 110 single phase even if there is "no such thing' as a 110 single phase outlet.

I have not surveyed every hospital in the US, so there might be some which have a receptacle in the hall for 220 and maybe even in a room. Kinda doubting having them in a patient room as there is no need for any device used there to consume high watt inputs, but hard to prove a negative. But there is no way that all single phase outlets are 208 as you stated in the first post by you that I quoted in this post. It was to that clearly erroneous statement to which I was and still am taking exception.

Denis

 

[Modelman]

Well, this has been educational (maybe) but has anyone noticed that the OP threw out this bomb as a first post, and hasn't been heard from since? He's probably home right now, happily toasting marshmallows over his glowing motor windings.

Dennis

 

[SeymourDumore]

Well, you have gone from saying all single phase units in all hospitals give a Proper 208 reading which is complete hogwash. T....
But there is no way that all single phase outlets are 208 as you stated in the first post by you that I quoted in this post.

Denis

Denis

From my experience, when in the USA someone is talking about a "single phase" supply or device or equipment or anything, they do in fact mean
2 hot legs ( L1 and L2 ), a Ground, and ONLY!!! in some cases a Neutral.

OTOH, I have never - in the last 31 years - ever heard anyone referring to a plane-jane 120V outlet as "single phase".

So, perhaps in your neck of the woods it is commonly accepted as such - in which case I apologize - in my area single phase means L1 and L2, 2 hot legs, line voltage, 240V or nothing but phase.
A standard 120V outlet or device or equipment is just that, 120V and is never called "single phase".

Or to put it in the perspective of the "machining" world, a Bridgeport or engine lathe typically uses 3 phase supply, an average size welder or compressor uses single phase, while
your computer is 120V regular power.

And yes, back in the mid 2000-s, ultrasound carts were humongous enough that a 120V supply would have required 30A or more, so they pretty much were
always much easier to be run off 208V "single phase".

Now as to the actual definition, I don't necessarily agree with the definition "single phase" as it really suggest 1 phase and 1 Neutral, but it is defined as such
in common terminology nonetheless.

 

[Jraef]

Wow, just... wow. Almost two, maybe three threads going on here.

Old machines I've worked on would say something like "Supply with Edison Circuit", meaning they wanted 220V and a neutral (and a ground) run out to the machine, as opposed to just 220V and a ground. So most likely he (the OP) is reading this off of the MACHINE control panel, not the motor nameplate. The motor is likely looking for 208V line to line, but the MACHINE uses 120V controls so for it to function correctly, the electrician needs to run 2 hots AND the neutral (and the ground) to it, aka "4 wire circuit", like a Dryer circuit. The REALLY old way of referring to that (prior to my birth, but still seen on machines in use in the 70s) was an "Edison Circuit" as previously described. We just stopped calling it that because the NEC started referring to the circuits by the numbers of WIRES and CONDUCTORS; a "4 Wire" circuit had 3 Current Carrying Conductors (L1, L2 and N) and a ground wire; a "3 wire" circuit had 2 CCCs and a ground wire.

Now, separate issue; can that 208V labeled motor survive being given 240V from a standard utility residential service? I'm with JST on this. Many new motors 5HP and under that are LABELED as "230V" are designed by the mfrs to accept 208-240V, whether they bother to say so on the nameplate or not. It is a conscious decision on the part of most MAJOR motor mfrs to avoid having to maintain larger inventories. Smaller / cheaper / foreign suppliers? I wouldn't trust it. But if a motor is LABELED as "208V" (which is doubtful by the way), or more likely "200V", then you CANNOT assume it is going to be OK with the higher saturation is will receive at more than +10%. So if it IS indeed labeled as 200V, and you DO happen to have an old "legacy" 220V system that MEASURES 220V at the point of connection, then it's likely fine. But just because you THINK you still have "220V" doesn't make it so. MOST utilities in the US have been supplying 240V for decades now. Not all, but most. So bottom line for the OP on this issue, don't just go by what the MACHINE nameplate says, start with the MOTOR nameplate and also take a measurement of what you REALLY have at the connection box. it can make the difference between success and failure. Edison circuit vs Edison "tap"? Semantics if you ask me.

Third quasi-thread on the existence of "208V single phase"? Really? This is a question? If I have a building fed with a 3 phase service and I need 120V plugs and lights, my choices are 240/120 3 phase 4 wire delta with a center tapped in which my 120V loads cannot exceed 5% of my transformer capacity, or I get 208Y120V, where it is 208V line to line and 120V line to neutral. Those are the ONLY choices in a 3 phase service (unless I want 480V and buy my own transformer for the lights and plugs). So of COURSE there is 208V single phase power available, it's available in EVERY 3 phase 208Y120V service; L1 to L2, L2 to L3 or L3 to L1, each of those is a 208V single phase circuit.

 

[dgfoster]

Denis

From my experience, when in the USA someone is talking about a "single phase" supply or device or equipment or anything, they do in fact mean
2 hot legs ( L1 and L2 ), a Ground, and ONLY!!! in some cases a Neutral.

OTOH, I have never - in the last 31 years - ever heard anyone referring to a plane-jane 120V outlet as "single phase".

So, perhaps in your neck of the woods it is commonly accepted as such - in which case I apologize - in my area single phase means L1 and L2, 2 hot legs, line voltage, 240V or nothing but phase.
A standard 120V outlet or device or equipment is just that, 120V and is never called "single phase".

Or to put it in the perspective of the "machining" world, a Bridgeport or engine lathe typically uses 3 phase supply, an average size welder or compressor uses single phase, while
your computer is 120V regular power.

And yes, back in the mid 2000-s, ultrasound carts were humongous enough that a 120V supply would have required 30A or more, so they pretty much were
always much easier to be run off 208V "single phase".

Now as to the actual definition, I don't necessarily agree with the definition "single phase" as it really suggest 1 phase and 1 Neutral, but it is defined as such
in common terminology nonetheless.

In my neck of the woods we use standardized language for power supplies:

Single-phase electric power - Wikipedia

To be clear, all outlets in patient rooms in all the hospitals I have worked or visited had only common household 110 single phase power outlets. Period.

Enough.

Denis

 

[Wild West]

Denis

OTOH, I have never - in the last 31 years - ever heard anyone referring to a plane-jane 120V outlet as "single phase".

Among electrical design folks and electricians it is single phase. They also refer to 220 (2 - 120V legs) as 2 phase. But you're right, in the everyday world it is called 120V.

 

[9100]

Around here, a 120-0-120 service and a 240 three phase line are common. They are completely separate in the building but the feeders in front of my shop are a high voltage three phase (I don't know what it is) and pole pigs to supply whatever is required. The single phase comes off a transformer across the street and he 240 corner grounded three phase comes from a different transformer at the street corner. Both come off the same HV feeders.

If the 80s are old, then I must be from the ice age because in the early 60s I worked in a plant with one of those miserable 120/208 services. Wall outlet voltage everywhere was 115-120, not 110, both at work and home. The plant had injection molding machines with 240 volt motors. On 208 they ran so hot you couldn't touch them. Maintenance put boost transformers on the heaters and they managed.

Later I consulted for another company with the same dismal service. They did a lot of military work and had a 75 KW MG that supplied 400 cycle power. It wouldn't start on 208. It was dual input 240 or 480 so we rigged transformers to supply 480 and it ran fine.

In my opinion the only value of a 120/208 supply is to save the building contractor money.

Also around here, what comes out of a 120 V socket is 120 volt single phase and a socket like the one in the link has 240 V single phase with a center neutral.

In the shop I have three line transformers connected to the 240 three phase line with the secondaries connected to give 208 and 480. Since in part of it I am only using one of the two windings of a given voltage, I only have half the rated power available, but that is enough for the few machines that need it.

Re military equipment, you can find a lot running on 208 or 416.

A two phase motor is a different animal. Two voltages are supplied 90 degrees apart. Tesla's original motors were two phase, not three.

Bill

 

[SteveBausch]

A look at the nameplate on the motor would probably clear all of this up.

Or the contactor coil voltage

Or the light bulbs on the work lamp

Or the duplex outlet for a radio, shop vac, etc

 

[jim rozen]

"In my opinion the only value of a 120/208 supply is to save the building contractor money."

Ah, no. Basically the question asked is: are there more 120 volt, single phase loads, or three phase loads?

If the answer is the first, then star connected 208 three phase is the natural route. Every hot leg is then
a potential source of 120. Costs just as much to do that as anything else. Those that really NEED 240 volt
power on their motors, get a boost transformer.

Hospital rooms? I've seen 240 volt heaters in there. But of course, hard wired, no receptacle.

 

[Tannewitz]

Two-phase electric power - Wikipedia

I have a old Nazel power hammer that was owned by Samuel Yellin

that was originally two phase as above.

 

[jonok]

I have three phase wild-leg power to my shop.

240 three phase between any leg, but on the "wild" or "high" leg it's 208 to the center-tapped neutral which gives me true 240 single with 120 control to center tapped neutral between the other two legs.

Works like a charm as long as you don't hook a single pole breaker to the orange leg...

 

[garyhlucas]

You know my first career was as an industrial electrical contractor and at one point I managed 18 electricians.

You guys are just scary! No way I'd offer an opinion around here!

 

[EPAIII]

I and most others here are very familiar with the way that power is distributed to homes in the US. It is called an "Edison circuit", but that terminology is somewhat out of use at this time. A more common term that is used today is "split phase" and that is the terminology that I would and have used.

But neither I nor anyone else has said above the we are not familiar with the terminology "Edison circuit". That terminology is easily found on the internet and other sources.

https://en.wikipedia.org/wiki/Ground_and_neutral#Shared_neutral

What I and others have said is we have not heard the terminology "Edison TAP". I did do an internet search and it failed to return any electrical references to that terminology other than this thread. Perhaps in some circles or some older text books the words "Edison tap" are used, perhaps as a way of originating a split phase circuit from 230 VAC, but I have not seen it and I do not know just what this term means. Is it an auto transformer with a center tap? Is it some special winding on a motor that acts that way? Or is it something else? "Tap" does seem to imply a transformer or some kind of winding. But I don't know and apparently no one else here does either. I have found myself in error many times when I have assumed something that seemed obvious to me at the time.

YIKES!

You have heard of an EDISON CIRCUIT before, it has been a source of discussion before.


It is a wiring technique where two circuits share a single neutral wire.
Commonly intended for 120 volt electrical outlets.

From Wikipedia:
A shared neutral is a connection in which a plurality of circuits use the same neutral connection. This is also known as a common neutral, and the circuits and neutral together are sometimes referred to as an Edison circuit.

This is pretty close but not complete
The Two shared circuits must not be the same circuit from the transformer. There should be 120 to neutral and 240 between the two circuits.
This way the neutral currents will cancel out.
Either circuit could alone carry the full rated current and the neutral would carry the full current.
If however, both circuits carry full current., the opposing neutral currents cancel out,
Thus no need for two full neutral wires as long as the two circuits cancel each other out.

Not convinced that this balances as perfect for a 208 (2 of 3 phase) circuit as well as a 240 volt single phase circuit.

Multiple circuits, as more than two, don't make sense ( to me ) as the combined neutral currents do not all cancel out.


But Really??? Suddenly no one heard of an Edison Circuit?

 

[EPAIII]

"Today, that 208 is often 240V. Correct?"

NO, NO, NO!

208 Volt is associated with THREE PHASE power. A three phase system that is wired in a Y configuration with 115 Volts from each let to neutral/ground will have 208 Volts between any tow of those three phases. I worked in a building that had three phase power and operated a 230 V motor on 208 Volts, between two of the three phases. And it worked just fine.

240 Volt (more nominally 230 Volt) is what you have in typical household wiring which is usually referred to as 110 V wiring (more nominally 115 Volt). The 240 V (220 - 230 V) is simply two times the 115 Volt that is found at most of the outlets in the house. And most household electric items use that 115 V power. A few, like ovens and dryers, use the 230 V power. Both of these are commonly called SINGLE PHASE or split phase which means split single phase.

Nothing changed in the 1980s or 1970s. Way back in the 1950s I measured the power in my parents house and it was about 115/230 Volts, SPLIT PHASE. There was no 208 Volts there unless the power company had problems. And that was a rare occasion. In the 60s I worked in facilities that had three phase and that three phase was 115/208 Volts as I described above.

Nothing has changed. As far back as I can remember, 115/208 V was there phase and 115/230 V was single, split phase. There have been other systems, but they go back further than that, further than the 1950s.

I get that JST, but please!

We're talking about a motor that is "old" ( as per the OP ).
Old can mean from 1980 yes?
So, back then 208 could just as easily be 192V. Correct?

Today, that 208 is often 240V. Correct?

Do you really think we have an epidemic of catastrophic old equipment failures due to voltage changes over the last 30 some odd years?

Is it optimal? By no means it is.
And yet, there are likely millions of old motors running day after day, week after week, year after year outside of their supposed 10% comfort zone.

My shop was originally built in 1979. Back then they've installed two roof ventilation units, both with a single phase 5HP motor.
The original plans specified 110V 3 PH supply ( I have the acceptance docs ), so we know that the motors ran on 192V.
Later on they've realized that 50KW furnaces draw ( and loose ) much less if they run on 240V.
So, in 1991 the outside transformer was changed to a 240V delta supply, and they've added a 240D/120Y tranny inside as a result.
And yet, the original 5HP fans remained wired to two hot legs of the incoming panel.

It is now 2017, and those motors are still original, running the very same 4' blades approx 6 hours each summer day.
192V from 1979 through 1991, and 240V from 1991 to present.

So yes, I would expect that an old woodworking machine can handle 240V single phase just as well.

 

[SeymourDumore]

You know my first career was as an industrial electrical contractor and at one point I managed 18 electricians.

You guys are just scary! No way I'd offer an opinion around here!

Well, please, do offer an opinion since Denis ( Dgfoster) gave you a like with his 40+ years in the medical field....

 

[SeymourDumore]

Nothing has changed. As far back as I can remember, 115/208 V was there phase ....

Obviously, math has changed since then....
'Splain in plain English how a 115V L-N reading is derived from a 208V L-L connection, or vice versa.

 

[9100]

Obviously, math has changed since then....
'Splain in plain English how a 115V L-N reading is derived from a 208V L-L connection, or vice versa.

Square root of 3.

Look up three phase theory and it will be plain. The two 208 points and the neutral are on a vector triangle, not in a straight line. Imagine a triangle 208 feet on one side and 120 feet on each of the others.

Bill

 

[9100]

I have three phase wild-leg power to my shop.

240 three phase between any leg, but on the "wild" or "high" leg it's 208 to the center-tapped neutral which gives me true 240 single with 120 control to center tapped neutral between the other two legs.

Works like a charm as long as you don't hook a single pole breaker to the orange leg...

I would much rather have a high leg service than a 120/208. Moving the neutral has no effect on motors except perhaps causing a trivial change in the insulation requirement.

Bill