208V 3-ph - no neutral

[Ken Amelin]

Yesterday I inspected a home with a 30KW electric water heater that was 208V-3ph and it didn't have a neutral connnection or ground connection to panel. It was mfg (and supect installed) in 1998.

1. Was this an OK thing when it was installed?
2. Is it leagal under today's code?
3. Is it a safety issue?

Thanks.

[Bill Kriegh]

No.
No.
Yes.

The water heater is required to be grounded. Looks to me like the wiring might be in conduit. If so, metallic, and continuous, the conduit can serve as the ground. There is no reason to have a neutral to the unit unless there are 120 volt accessory items attached (unlikely)

The obvious issue beyond grounding is the white wire on a phase connection.

Electric water heaters are very dangerous when ungrounded. The failure of an element can put line voltage on the tank.

[Philip]

3 phase in a residence? Was there two seperate service entrants?:confused: .

[Ken Amelin]

One multi-unit building. Multiple service entrances for 4 separate units.
This unit has only one distribution panel.

[Philip]

How do you get 120v 60Hz off of a feeder of 3 phase 208volts?:confused:

[Joe Dach]

How do you get 120v 60Hz off of a feeder of 3 phase 208volts?:confused:

The voltage between any feeder and neutral is 120 volts. The voltage between any feeder and another feeder is 208 volts.

On 3 phase services each feeder (phase) is 120 degrees apart instead of 180 degrees like 120/240 split phase.

[Kary Krismer]

So it's 240 you can't get off 3 phase, right?

I've never understood the advantage of 3 phase over 2 phase. Is it that you can get two high voltage circuits off of three lines, where with 240 that would require four lines?

[Joe Dach]

So it's 240 you can't get off 3 phase, right?

Right




I've never understood the advantage of 3 phase over 2 phase. Is it that you can get two high voltage circuits off of three lines, where with 240 that would require four lines?

3 phase electric motors are more efficient and have more power. All the power lines from the power plant are three phase and most industrial buildings are also but usually higher voltage like 277/480.

[Lou Romano]

Kary Krismer;So it's 240 you can't get off 3 phase, right?



You can have 240-volt 3 phase Delta!

[Rollie Meyers]

So it's 240 you can't get off 3 phase, right?

I've never understood the advantage of 3 phase over 2 phase. Is it that you can get two high voltage circuits off of three lines, where with 240 that would require four lines?

2 phase is obsolete & 600 volts and less is LOW voltage.

[Philip]

2 phase is obsolete & 600 volts and less is LOW voltage.
When did all this happen?:confused:

[Ken Amelin]

Quote:

Originally Posted by Kary Krismer http://www.inspectionnews.net/home_inspection/images/ca_evo/buttons/viewpost.gif (http://www.inspectionnews.net/home_inspection/electrical-systems-home-inspection-commercial-inspection/20359-208v-3-ph-no-neutral-post134393.html#post134393)
So it's 240 you can't get off 3 phase, right?


Right

If you can't get 240V from 208V-3PH - what is the voltage for the two pole breakers in the panel as shown in original photo?

[Rollie Meyers]

When did all this happen?:confused:

You are confusing single phase and 2 phase they are 2 different systems.

[Rollie Meyers]

If you can't get 240V from 208V-3PH - what is the voltage for the two pole breakers in the panel as shown in original photo?


208 volts, they would have 208V on one of the single pole breakers instead of 120V, if it was a 120/240V 3Ø system. W/ 120/240V 3Ø, 2 phases are 120V L-N and 1 is 208V* L-N, & 208Y/120V all phases are 120V L-N and L-L is 208V.

*Code req. that phase be the "B" phase and be identified orange, on older installs it could be the "C" phase & be identified red, that is just another reason to verify everything.

[ken horak]

It would be extremely helpful if the original post included the wiring method to the water heater. Conduit ? Cable? Type of cable? type of conduit?

[Ken Amelin]

It was connected by cable, but the type is not visible in photo, sorry.

[Philip]

So wel should never encounter a two phase syste,:confused:

[Kary Krismer]

This thread is raising more questions than answers for me, but they're at least all theoretical.

How do utilities provide both 2 phase and 3 phase power, since 240 needs the legs 180% out of cycle and 208 needs 120 degrees out? Can they just transmit everything 3 phase and then somehow shift the phase of one leg to provide 2 phase power?

[chris mcintyre]

How do utilities provide both 2 phase and 3 phase power,...


2 phase is obsolete....


You are confusing single phase and 2 phase they are 2 different systems.

It can be confusing.

[Jerry Peck]

How do utilities provide both 2 phase and 3 phase power, since 240 needs the legs 180% out of cycle and 208 needs 120 degrees out?


It is not "2 phase", there are "2 phase legs on the same phase", but it is "single phase".

Take the neutral out of 240 volts and you have a simple single phase circuit with the current going in one leg, through the load, then out the other leg, that process repeats itself 60 times a second, i.e., "60 cycles", or "60 Hertz" of "60 Hz".

[ken horak]

It was connected by cable, but the type is not visible in photo, sorry.

And that cable did not have an equipment grounding conductor in it ?

[Ken Amelin]

Ken - No Grounding conductor in that cable.

[Kary Krismer]

James, thank you for your lengthy explanation. I'm not necessarily seeing the distinction between acting like separate phases, and actually being separate phases, except that I guess they are just off one of the three.

But my question originally is included the question how do they get the one leg to be 180 degrees off from the other?

[Jim Port]

No grounding conductor because the service is three phase and the heater does not need it. JR

JR, I think you should review the difference between a groundED and groundING conductor. While both would be connected to the same point electrically in a service panel the purposes are entirely different.

Regardless of single phase or three phase the unit should have a grounding means.

[Kary Krismer]

Thanks again. One more question, and this is really far afield.

Why do utilities seem to try to balance the phases within small geographic areas? In almost every residential area you see three lines, when probably none of the houses have 3 phase power. I can see the benefits of having the entire system balanced, but to do so in small areas just seems wasteful since you need to run three lines through each neighborhood.

[Jerry Peck]

Ken - No Grounding conductor in that cable.


No grounding conductor because the service is three phase and the heater does not need it.

The "grounding" conductors is required, how else is one to "ground" the water heater?

I believe you are meaning "neutral" conductor.

By the way, the "grounding" conductor could be metal conduit.

[Bob Winchester]

WOW is all I have to say.
The voltage is determined by the turns ratio in the transformer. It's got nothing to do with where the neutral is tapped from in the tranformer configuration. 208 volts is a WYE configuration and 240 volts is a DELTA configuration of transformers. 208 volts always has a neutral. It is the common conductor tied to all 3 transformers and provides 120 volts from any hot wire to neutral. 240 volts in 3 phase has the "wild leg" with the higher voltage to neutral when it is a 4 wire system. One of the transformers had a center tap on the transformer to give a 120/240 volt condition. This is what normal houses have to supply them, a single transformer with a center tap neutral. When you go to 3 phase you get the high leg to neutral but the 3 phases are 240 volts from phase to phase. Some eqauipment is 240 volts and NOT rated for 208 volts. With motors this could be a problem. You do not get more power with 3 phase as in a 3 HP motor has more power if it is 3 phase than if it is single phase.
It is correct that a ground must be run with the circuit conductors to ground this water heater. I just wonder why it's connected to a 100 amp breaker and it's only 10,000 watts per phase. The conductors would have to be #4 in order to be connected to the 100 amp breaker.
If the white conductor has black tape or a marking of some kind it is fine to use it for a current conductor. This marking identifies it as a current carrying conductor instead of a grounded conductor.
Be careful using "grounding" and "grounded". As stated above they have entirely different purposes and are not the same.
If you want to learn more about this type of thing look for some classes given by the IAEI, International Association of Electrical Inspectors, on the topics you want to learn more about.
And just think, I was told that Electrical Inspectors are just Home Inspector "wannabees". I guess this question just proves that goofball to be wrong.

[Rich Goeken]

And it can get VERY interesting if the sparky gets the phases swapped during installation, and then they turn something on.

[stanley labinsky]

Good morning, gents... and ladies, if present.

While I'm not in the building trades industry (I'm here to learn about how things should be done... correctly), one of the courses required as part of my voc/tech high school electronics education... back in the late fifties (no, not eighteen fifty!), was residential wiring with a smattering of motor wiring... bending and threading black conduit and EMT, Romex, twist solder and tape the connections (wire nuts were something new back then)... three way and four way switches... I'm now in 2-way radio and school bus surveillance equipment installation and maintenance these days and hold an Amateur Extra license... I've even built stuff, and not just from kits.
Back then, in Philadelphia, there were actually TWO PHASE motors.
Really, you might say, how do you identify such an animal? Simple, it had two windings (four leads), both of which had to be constantly connected to an AC power source for the motor to turn. It had NO start switch, relay or capacitor. The supplied voltages (phase A and phase B) were actually displaced NINETY degrees from one another.
So, when I see the mention of TWO PHASE, being said in the same breath as single phase, for me, red flags go up.
It's either three phase (120 degree displacement, phase A, to B, to C) or single phase (zero degrees displacement).
The idea of single phase having two phases comes from a misunderstanding and mis-use of phase.
Here it is really a matter of which end of the transformer's secondary you look at - what is your point of reference.
Looking at L2 from L1 (or at L1 from L2) in a single phase circuit, you see no phase displacement, just 240 VAC.
Looking at L1 (or L2) from the mid-point ground connection of the pole transformer's secondary: when L1 is at 120 volts to ground, POSITIVE, L2 will be the same potential, just NEGATIVE. But, they are NOT displaced from each other in TIME, just POLARITY... a huge difference, not just a bunch of semantics!
At one instant in time (repeating a hundred and twenty times every second) you can even measure ZERO volts L1 to L2 to ground/neutral. You cannot see that in three or two phase power, measuring from phase to phase!

As regards the why of load balancing in a neighborhood, IIRC, load imbalance is passed back to the primary of the substation transformer and back into the distribution system. Having the bulk of the current being supplied by one phase requires the substation transformer to be wound with much heavier wire and to have a much larger core. I'll guess that the pole wiring is less expensive than the monster transformer and heavier feeders and wasted energy that might be involved.

Good discussion, though...

Stan

[Kary Krismer]

Stanley, on the neighborhood issue I was thinking more of say running one phase to the NW of the substation, one to the NE and one to the South, such that each area was 1/3rd of the total. I can see where the current system gives them a lot of flexibility, but at a lot of cost. If there's no other benefit, I'd question the cost.

[Bob Winchester]

If you have overhead wiring it's easy to see which phase your transformer is connected to. The 3 overhead wires are each a phase of the primary and the lower wire between poles is the grounded conductor. A residential transformer will be connected to one or another of the 3 phase conductors of the primary and also to the grounded condcutor below. If your phase is loaded heavier then it would be easy enough to change the supply to another phase right at your transformer. This way a utility can adjust the balance of the system in the neighborhood.

[stanley labinsky]

I did a little digging and apparently, Kary, from the comments in:

Three-phase power systems : POLYPHASE AC CIRCUITS (http://www.allaboutcircuits.com/vol_2/chpt_10/2.html)

the difference is greater than I had originally assumed.

Stan

[Jerry Peck]

WOW is all I have to say.
The voltage is determined by the turns ratio in the transformer. It's got nothing to do with where the neutral is tapped from in the tranformer configuration.


WOW is all I have to say. :p

"The voltage is determined by the turns ratio in the transformer." Correct.

"It's got nothing to do with where the neutral is tapped from in the tranformer configuration." Incorrect.

Take a 240 volt winding and tap it in the middle, what do you get? Why, 120 volts / 240 volts and you did not change the windings in the transformer at all, all you did was tap it off at the center.

I believe most of here understood what you were TRYING to say, but, because you did try to down grade everyone else with your post, let it be known that YOU were NOT correct in your post in its entirety.

Does that make you as stupid as all the others you implying in your post? Looks that way. :rolleyes:

[bob smit]

Three phase always evokes much discussion in any circle, no exception here.
One of the two utilities serving my jurisdiction was running 208 3ph without suppling a grounded conductor to the metering equipment.
Furthermore, they don't allow any grounding conductors in their meter enclosures.

This was for services to supply only 3ph equipment. I could only have the contractor install a good grounding system on the premises.
This situation has ceased to be employed by the utility (hopefully because of my nagging), but I have always wondered how the well the equipment would function when the load was not perfectly balanced. Also, we know how the grounded conductor can carry even more load when harmonics are incurred in a Wye configuration do to capacitive and/or inductive reactance.

Now that we all understand 3, poly, split, 2, single phasing,... shall we bring up corner grounded delta? (my favorite).
Or, shall we discuss why utilities transmit at such high voltages only to step it down, I squared R losses, and ungrounded primarys.....I can't wait
Bob Smit, County EI

[bob smit]

CG Delta is just one of those odd balls that wakes us from the day-to-day slumber we find ourselves in, or maybe just I.
Such as but not limited to: no fusing in the grounded phase,(3 pole common trip breaker is allowed), special marking of the grounded phase throughout.....

The installation or inspection never fails to provide interesting discussions on the job site.

The Utility enjoys the no-load losses that would be incurred if they had to supply a transformer with a 4-wire secondary. Remember that transformers have losses even when there is no load applied....inductive reactance, eddy currents and the like.
Bob Smit, County EI

[Philip]

Let us not forget hysteresis losses within the transformer. :)

[bob smit]

OK James, U have me interested, i.e. super conductor. Last I read there was the ambient temp issue that was the next hurdle to jump. Perhaps some new material I'm not aware of?
Bob Smit, County EI

[bob smit]

Philip: Lets not forget besides hysteresis (core resistance to magnetic flux) and eddy (circular currents): we have skin effect (which is why the use of small diameter windings), including magnetstriction, dielectric, and mechanical losses (buzzing). All but the mechanical loss is loss in the form of heat generated.

It's a wonder we get any power out of the secondary at all.
These losses are summed up as the 'Z' factor when doing short circuit calculations, usually in the 2.5 - 7% range.

Utility xformers have got more efficient over the years, I've noticed, while doing these calc's.

Note that the 2008 NEC now requires the available fault current at the main terminals to be marked on the service equipment for commercial/industrial installations. This requirement was added to inform service personnel that any replacement main devices need at least that rating.
Bob Smit, County EI

[Philip]

Ahhh, the power of the Electric Motive Force. I have for years wondered why we did not just harness the force of magnetism without converting it to electricity. Now there are magnetic motors in development, you can google it.:)

[Luigi NI]

My 1st post here so bare with me
from my work with 3phase you need a ground system
don't count on the emt to ground anything run a separate ground wire
our 3 phase does not handle 120 to ground it is a (false) voltage carries no current
the use of any 2 legs will produce 220 to run (single phase ) equipment
you can use a transformer to drop down voltage to 120 for (other) appliances
most commercial property in my area carries both 3 phase and single phase
that panel should still have a ground wire to earth and the poll to ground the 3phase transformer on the poll