Help me to identify my service panel for a subpanel work

[John Lanciani]

Thanks Rollie, the breaker rating makes perfect sense as to why not to use the high leg for single phase. I did some more digging this morning and it seems that the bigger problem with these types of services are on my (the utility) side of the house. Depending on the transformer primary connections there can either be over heating issues or over voltage issues if one of the three windings is de-energized. There is also a de-rating issue for the center tapped transformer to account for load imbalances.

Ruhi, I talked with our two senior engineers this morning and they agree with my opinion that there is an issue with the voltages you are seeing. You should give your utility a call and have them investigate before you proceed.

[Rick Christopherson]

This is a fairly common setup in light industrial areas and is called an Open Delta, Center-tapped Delta, and a few other names. (Shown to the right in the image below). The benefit is that it provides the 120/240 for single-phase while also providing 240 3-phase. What's kind of odd is that you have only the one 3-phase load on the lower left side. It's a fairly expensive connection for just a single 3-phase load.

For 240 volt single-phase loads, you are permitted to use any combination of the phases (as is already done in your panel). As pointed out, the high-leg was supposed to be connected to the B-phase, but that is not something that should be "repaired" after the fact (what's done is done).

I do see that there are a couple single-pole breakers on the high-leg. This is not correct. The biggest problem for you is that these loads are getting lower voltage than they prefer. If you can relocate these to a 2-pole breaker, I would recommend it.

Because your bottom breaker location is on the high-leg, I would relocate the 3-phase breaker down one position, but rotate the wires to be white, black, red (from top to bottom). This will keep phase rotation the same and the motor will still rotate in the correct direction.

Your C-phase voltage is slightly high, but at only 8 volts over, it's not a big deal. That's only 3%. (The C-N voltage is immaterial because no load should be using it.) This elevated voltage doesn't impact any of your single-phase loads, but the one 3-phase load you have will have a slight imbalance.

For your subpanel, use A, B, and Neutral the same as you would for normal single-phase.

[Paul McGaha]

Ruhi,

That is a fairly rare commercial service configuration.

I've been doing electrical work since 1977 and you just dont see that very often.

It was an idea that engineers got away from at some point. For the most part anyway.

Stunned to see one in your house.

The manufacturer of the panel looks to me to be ITE.

PHM

[Ruhi Arslan]

Panel is Siemens Murray Type H Class CTL (maybe CLT). IT was installed in 01/2001by the looks of the date on the inspection sticker.

This has been a very informative thread for me. John's suggestion to be cautious about this configuration intrigued me to learn more about it. As I was searching for some reading material, I came across a discussion on exactly the same topic; high-leg use. After reading sifting through 16 pages of postings at this one particular forum which is attended by the "trade" engineers, consensus was far from conclusive. Common theme is though not to use it or if must use the proper breaker for it which is not easy to find. It cannot be used with "slash" rated breakers.

I am taking your advice and making changes as suggested. First thing first, shop's 220V line is now moved to a double pole A-C (248V measured) which was vacated from a decommissioned window AC unit. I have the oven, dryer and a couple of electric baseboards now sharing the high-leg. Except oven none is needed but I am not going to remove them for future use just in case.

Rick,
I will use A, B and Neutral for the subpanel for the shop. In regards to relocating the 3Ph breaker on the lower left, it is on B-C-A in that order. There is one more slot at the very bottom which is C. If I were to move it down to use A-B-C, and keep the same order for each wire, A to A, B to B and C to C, would that be correct for the phase order?

Inside the panel, there is sticker instructing to use the B (center leg) for the highest voltage but I guess the installer didn't have his/her glasses to read it during the install.

[Rick Christopherson]

I have the oven, dryer and a couple of electric baseboards now sharing the high-leg. Except oven none is needed but I am not going to remove them for future use just in case.

To avoid your own personal confusion, don't think of the C-phase as being high-leg unless it involves the Neutral (which it shouldn't). When no Neutral is involved, it is not a "high-leg". It's just 1 phase out of 3 available. (Such as with your woodworking power tools).

However, I would not use the C-phase to an appliance that might be using the ground as a current-carrying conductor, such as Ovens or clothes dryers. (It's actually the Neutral that is being used as a ground). Older appliances used a 3-wire circuit without a ground, so even though it appears there is no Neutral, there actually is. In this case, your low-voltage controls have a 50/50 chance of either getting the 120 volts they want, or the 208 volts that will toast them. If your appliance has the NEMA 10-30 plug shown below, then make sure they are A-B-N, and not C.
10_30p.gif

Rick,
I will use A, B and Neutral for the subpanel for the shop. In regards to relocating the 3Ph breaker on the lower left, it is on B-C-A in that order. There is one more slot at the very bottom which is C. If I were to move it down to use A-B-C, and keep the same order for each wire, A to A, B to B and C to C, would that be correct for the phase order?

If this was a raw motor circuit, then technically you don't need to change the wires at all. I mentioned it previously so the C-phase remained the C-phase just in case there were 120-volt loads inside the appliance, yet still maintained the same rotation. The phase "rotation" will still be the same. ABC=BCA=CAB. Reversed phase rotation would be CBA, BAC, ACB. Reversed phase rotation will make the motor turn backward. (However, if it is already reversed, then leave it reversed. It could be corrected somewhere else in the connection.) Keep the C-phase where it is, and maintain the same rotation.

That is a fairly rare commercial service configuration.

I've been doing electrical work since 1977 and you just dont see that very often.

It was an idea that engineers got away from at some point. For the most part anyway.

Stunned to see one in your house.

Just because you don't find it used in your area does not mean it is rare or some type of abomination. It has a distinct purpose, and it is not that rare. You won't find it very often in "Industrial" locations, but you will find it in "Light Industrial" locations. Yes, it is rare in residential areas, but not if they overlap Light Industrial or agricultural.

[Rick Christopherson]

There is one more slot at the very bottom which is C.

Oh, the previous electrician did label this last breaker as using a single-pole breaker at 208 volts (the red tape), so if you do make this shift, make sure this circuit gets converted to a 2-pole breaker at 240 volts.

This wasn't supposed to be this complicated, but the previous electrician didn't have a clue what he was doing.

[Paul McGaha]

Oh I dont know about that service not being rather rare. In the projects I've been involved with in my career I'd for sure say they're quite rare.

120/208, 3 Phase, 4 Wire, Service far more common than a high leg service. And if the panel is serving mostly phase to neutral loads you dont have all those unusable pole spaces.

I'd like to see some others chime in about how often they see a high leg service as compared to conventional Y Service. If you took all the commercial or industrial services there are out there and compared how many were high leg and how many were Y Just a guess but I bet its not 1 out of a 100.

Ruhi, This is not meant to offend. If you wind up with some 3 phase, 240 volt equipment you are going to be so good to go.

PHM

[Ruhi Arslan]

To avoid your own personal confusion,

Too late....

[...] don't think of the C-phase as being high-leg unless it involves the Neutral (which it shouldn't). When no Neutral is involved, it is not a "high-leg". It's just 1 phase out of 3 available. (Such as with your woodworking power tools).

I am interpreting above statement as I can use all my woodworking power tools (band saw 220V, table saw 230V, jointer/planer 220V, DC 220V, mortiser 220V) using a double breaker from C-A or C-B using one of these plugs;

23305.jpg

Since the X and Y are interchangable, it doesn't matter where the C goes to (X or Y). There is no Neutral but there is still a Ground.

However, I would not use the C-phase to an appliance that might be using the ground as a current-carrying conductor, such as Ovens or clothes dryers. (It's actually the Neutral that is being used as a ground). Older appliances used a 3-wire circuit without a ground, so even though it appears there is no Neutral, there actually is. In this case, your low-voltage controls have a 50/50 chance of either getting the 120 volts they want, or the 208 volts that will toast them. If your appliance has the NEMA 10-30 plug shown below, then make sure they are A-B-N, and not C.
10_30p.gif

Not with the oven (it is on A-B legs) but dryer is on C-A with the plug like you posted earlier.
At the dryer plug, W-X reads 120V, X-Y reads 240V. I am not using it but thats how it's been when we moved in. Baseboard heaters are also using the C leg.

If this was a raw motor circuit, then technically you don't need to change the wires at all. I mentioned it previously so the C-phase remained the C-phase just in case there were 120-volt loads inside the appliance, yet still maintained the same rotation. The phase "rotation" will still be the same. ABC=BCA=CAB. Reversed phase rotation would be CBA, BAC, ACB. Reversed phase rotation will make the motor turn backward. (However, if it is already reversed, then leave it reversed.

I moved the three breakers down to ABC maintaining BCA order. It freed up an A-B spot for the subpanel. It would be nice to have a 3-Ph panel in the workshop but I don;t think I'll ever buy any equipment which is not 1-Ph. If I end up finding something, I'll always have the option to have a line form the service panel.

This has been a very informative discussion for me. I've learned enough to be dangerous now.

BTW, I've called the POCO to put them on notice that I have "abnormal" voltage. I received a call a bit earlier from a troubleshooter. He was given misleading information as such that I had no voltage on some phases. Once I've explained to him, he understood and made a request voltage to be checked and adjusted as needed. But he assured me that I don't have to worry about high voltage. Also, he informed me that there are other houses fed from the same transformer with similar setup. He said some of the houses based on the size required this configuration (my house is about 5000sqft).

I made one more voltage check at this hour; 124, 238 and 258V @ 10pm.

[Rollie Meyers]

For a 240V load you cannot go to a big box store* for a 2-pole breaker if going to use the high leg & any other phase for a 1Ø load because the the breaker must have a 240 volt rating, the more common 120/240V type is not permitted as the lower rating exceeds the avail. voltage. BTW, the panel does not comply w/ the NEC requirements in effect at the time of installation. Here is a copy & paste from the 2008 NEC.

408.2(E)

(E) Phase Arrangement. The phase arrangement on
3-phase buses shall be A, B, C from front to back, top to
bottom, or left to right, as viewed from the front of the
switchboard or panelboard. The B phase shall be that phase
having the higher voltage to ground on 3-phase, 4-wire,
delta-connected systems. Other busbar arrangements shall
be permitted for additions to existing installations and shall
be marked.
Exception: Equipment within the same single section or
multisection switchboard or panelboard as the meter on
3-phase, 4-wire, delta-connected systems shall be permitted
to have the same phase configuration as the metering
equipment.
FPN: See 110.15 for requirements on marking the busbar
or phase conductor having the higher voltage to ground
where supplied from a 4-wire, delta-connected system.

There are some differences in wording in the 1996 & 1999 editions but the requirements are pretty much the same.


One method that is done is to have a 100A single phase panel next to the 3Ø panel, this eliminates any worries about dealing w/ the high leg & no need to buy very expensive & special order 240V rated breakers.(I have heard a cost of about $90.00 ea, VS $8.00 or so for a 120/240V rated).

[cecil rolfe]

In my 30 year career in electric distribution in Wisconsin, 120/240 delta was most common, used in commercial and light industrial. 120/208 in offices and schools some commercial.
120/240 out numbered 120/208 50:1.

Cecil

[Bob Varney]

Just think of all the three phase equepment you can get deals on, with out getting a phase converter.

Bob

[Van Huskey]

I find this thread though not remotely applicable to me none the less fascinating. The one thing that hits me is I wondered if Ruhi is getting nailed on electrical service costs, lots of utility companies charge a minimum and or a premium for any sort of 3 phase service. Just wondering if it is the case here. I will say without the premium I would love to have 3 phase power.

[Ruhi Arslan]

The one thing that hits me is I wondered if Ruhi is getting nailed on electrical service costs, lots of utility companies charge a minimum and or a premium for any sort of 3 phase service. Just wondering if it is the case here.

Not sure there is a premium for 3Ph service but since because I also have ON/OFF peak hour metering, I think the average comes to about the rates for PSEG. $0.17 for peak, $0.075 for off peak, in average comes to $0.11/kWh for me.

I've checked all my breakers. None of the 240V circuits using the "high-leg" are 240V breakers but all 120/240V. I found 240 double pole breakers online but they are about $100+ each based on the amperage.

[Jim Neeley]

Ruhi,

While I'm electrical engineer, I hadn't seen your type of install before so I forwarded the first 4 pictures to another electrical engineer I work with who has experience in commercial power (mine is all industrial, which is 480V, plus instrumentation and control systems). I'll paste his return email to me below. When reading it, please recognize that in the first paragraph he's talking about how it should be wired and beneath that, talks about what is incorrect. Also note that he did not have the benefit of yor voltage measurements but was talking about what it should read.

As recommended by others, get local feedback.

Jim,

That’s not a residential panel. It’s a Sq.D QO type panel.

They don’t supply 3-phase to residences.

What it is, is a 3-phase delta, grounded at the mid-point of one phase.
If you put a volt-meter on this Phase to phase you’ll get 240 for all combinations, A-B, A-C, B-C.
If you measure voltage at each phase to neutral (ground), you’ll get 120 A-N, C-N, but 208 volts on B-N.
You can see that in the diagram in your second photo.
Also note in photo 4 that it is mis-wired.
The 208-N leg or ‘wild leg’ or ‘high leg’ as it’s known in the trade is ALWAYS supposed to be Phase B, the middle phase and its always marked with orange per NEC 110.15. In this case, CC-N would be the wild leg.

Tim

[Rollie Meyers]

Ruhi,

While I'm electrical engineer, I hadn't seen your type of install before so I forwarded the first 4 pictures to another electrical engineer I work with who has experience in commercial power (mine is all industrial, which is 480V, plus instrumentation and control systems). I'll paste his return email to me below. When reading it, please recognize that in the first paragraph he's talking about how it should be wired and beneath that, talks about what is incorrect. Also note that he did not have the benefit of yor voltage measurements but was talking about what it should read.

As recommended by others, get local feedback.

Jim,

That’s not a residential panel. It’s a Sq.D QO type panel.

They don’t supply 3-phase to residences.

What it is, is a 3-phase delta, grounded at the mid-point of one phase.
If you put a volt-meter on this Phase to phase you’ll get 240 for all combinations, A-B, A-C, B-C.
If you measure voltage at each phase to neutral (ground), you’ll get 120 A-N, C-N, but 208 volts on B-N.
You can see that in the diagram in your second photo.
Also note in photo 4 that it is mis-wired.
The 208-N leg or ‘wild leg’ or ‘high leg’ as it’s known in the trade is ALWAYS supposed to be Phase B, the middle phase and its always marked with orange per NEC 110.15. In this case, CC-N would be the wild leg.

Tim

That panel is NOT a SQ D! The main is a ITE (now Siemens) QJ2 frame breaker & the branch breakers are Siemens QP or Siemens Murray MP frame breakers. (They look the same from a distance).