Help me to identify my service panel for a subpanel work

[Ruhi Arslan]

I have a rather unusual service panel (main panel) at my house. House is from 50s but panel was replaced not long ago by previous long time owners. Besides having an on/off peak time meter, panel has three hot feeds coming into the panel. Depending on which lug bar you choose, you could get 110, 220 or 440V circuits. Every third breaker (marked with red tape) is 220V. If I were to add a subpanel for the shop with 220 and 110V circuits, which arrangement of breakers could be used from the service panel? I have more 220V slots available on the panel. There were quite a few 220V baseboard heaters with dedicated circuits which are not used anymore. I already have another subpanel upstairs which are for most of the house except, AC, furnace, oven, etc. I am not even clear how and what to ask but I am hoping that as more questions come up, I would try to clarify more. I already have 2-2-2-4 Al cable and a 100A panel ready to be installed indoor to indoor.

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http://www.sawmillcreek.org/images/misc/pencil.png

[cecil rolfe]

Do you have 3 phase? That voltage and diagram looks like 120/240 delta 3 phase.
Cecil

[Ruhi Arslan]

If I don't know, does it mean I don't have 3 phase service?

[John Lanciani]

Hi Ruhi,

If you could take 2 more pictures, one closeup of the electric meter nameplate and one of the service entrance attachment from the street, it would be helpful in identifying for sure what you have but every indication is that it is a 4 wire delta service. If it is, and you are not very well versed in electricity, the potential for bad things to happen is rather high. I'm all for doing things yourself, but I'd strongly caution you against it. (The utility I work for does not even allow this service in a residential setting, primarily for safety reasons)

[Ruhi Arslan]

First picture is the supply side, second is to the panel and the last one is the face plate of the meter.

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What makes it "dangerous" when it is 3Ph besides being dangerous anyway?

[John Lanciani]

Hi Ruhi,

Definitely a 120/240volt 4 wire delta service. The biggest issue is that the "high leg"- the one with the red striped tape - is 208 volts to ground. If you lose track of it, or you simply weren't familiar with it, you could easily connect a 120 volt load to that leg and burn up equipment.

There is no 480v (440) in that panel. If you intend to feed a single phase 3 wire 120/240v panel from this service it is imperative that you connect to the correct busses in the panel. you do not want to connect single phase equipment to the high leg under any circumstance.

[Ruhi Arslan]

Here is what I measured between the line-to-line and lines-to-neutral; (A, B, C are lines, N is neutral)

A-N : 120
B-N : 120
C-N : 224
A-B : 240
A-C : 248
B-C : 248

By "high leg" do you mean "C-N"? For the three wire 120/240V panel, I could do one A, one B and the N to subpanel then? I also will have the ground but neutral/ground bar is separated on the subpanel.

[John Lanciani]

Your idea on the connections is correct. C is the high leg, and the voltages are a fair bit higher than I would expect to see. Either C leg has no load on it or more likely the transformer out on the street has the windings tapped incorrectly. In the system where I work those voltages are out of spec, I'd be generating a work order and we'd fix it ASAP.

Acceptable voltages for your service configuration in our service area are;

A-N 116-122
B-N 116-122
C-N 202-212
A-B 232-242
B-C 232-242
A-C 232-242

Measured at the meter base (with a calibrated true rms meter).

Edited to add: Do you know why the previous owners had a 3 phase service installed in the home?

[Ruhi Arslan]

I think I am sitting on a potential trouble with all my 220V equipment then. My table saw, band saw, DC, mortiser all on the circuits fed from C-N at 224V (no load). If I am understanding correctly, are you saying that there is a mistake have been made when they were connecting to the transformer which is on the utility pole right behind my house, so if someone changes to correct it, I may get higher voltage on my C-leg to burn my equipment?

I took the measurements with a digital Fluke at the meter base.

We don't know why the 3-phase but it was not the only peculiar thing here. My guess is the AC compressor - it is a monster. There were two independent layers of security system and estimated to be 100+ phone lines. It was a tax exempt "rabbi residence".

[David G Baker]

Ruhi,
It is time to hire a professional. If you do not throughly understand your system call a pro. If you don't need or want the 3 phase setup have your system rewired to meet your needs.

[Ruhi Arslan]

It is time to hire a professional. If you do not throughly understand your system call a pro.
The scary part is the fact that an electrician did the wiring for the 220V. He stated that he's never seen a panel like mine but he suggested that I would only use one breaker space the way he did it.

[John Lanciani]

The scary part is the fact that an electrician did the wiring for the 220V. He stated that he's never seen a panel like mine but he suggested that I would only use one breaker space the way he did it.

You need to find an electrician that works on commercial and industrial equipment. If the electrician that you hired hadn't seen anything like you have, he should have politely declined the job (I firmly believe that there should be grades of licences for electricians and other contractors just like there are for truck drivers.). The service that you have is fairly rare today, but it is not unheard of (except in a residence).

The high leg -C in your case- should actually be lower (208v nominal) but as I mentioned you should not have anything connected from C to N. Please proceed cautiously...

[Ruhi Arslan]

The high leg -C in your case- should actually be lower (208v nominal) but as I mentioned you should not have anything connected from C to N. Please proceed cautiously...
John,
Thank you very much for your time. I take your caution seriously and won't run anything till I can have some one who is familiar with this setup to come and correct it accordingly.

Just for my benefit to better understand; since I have two of the phases at 248V (A-C and B-C) but center tap at exactly 120V (tapped in between A and B), high leg C should be 217V not 224V as it is measured. The math I use is square root of (square of Va - square of Vb). Math doesn't add up. If I wee to measure 217V at the high leg (C in my case), I would say it is normal because A-C and B-C are 248V.

Since you've alerted me, I've been reading some more and came across quite a few "opinions" to the fact that it is OK to use high leg for single phase loads as long as the lines are clearly marked as such. What is the reason in a nut shell, not to use the "high-leg" to supply single phase motors. All my motors specify 220V only or 115/230V. If I were to use the "traditionally common" 120-120V to get 240V (A-B in my case) or in between the other phases to get 248V (A-C or B-C in my case), supply voltage would be higher than specified for the equipment. Wouldn't it make more sense to use the high leg with 224V? Again, my question is because I don't understand the reason to be cautious with the high leg. Thanks so much again for taking the time to help me understand. I hope it benefits others as well...

[John Lanciani]

Ruhi,

A couple of things; my 22 years of utility work, 15 of which have been spent dealing with power quality issues are telling me that the transformer feeding the C phase of your service is either tapped incorrectly or has a winding short. the C-N voltage should be 208 and A-C and B-C should be 240. All of them are significantly higher than they should be based on your readings.

A few of the concerns with connecting single phase equipment to the high leg are;

1. Even if you mark it well, someone in the future will screw it up and or get hurt as no-one is expecting to find a conductor with 208 volts to ground on it (in a residance).
2. Many single phase motors and contactors are not rated for 208 volts, a 230 volt motor will run very hot.
3. It tends to screw up the balance on the transformer bank if you have a ton of load connected to only the high leg, this can impact the other two legs in a delta connected transformer bank if the transformer impedances aren't matched
4. I'm not 100% sure, and I don't have a code book at home, but I suspect that there are issues using a single pole breaker for a 208v load.

[Rollie Meyers]

Any circuit breaker that is between the high leg & any other phase must be rated 240 volts (very expensive ) a standard residential breaker is rated 120/240 volts & not permitted to be used on the high leg, BTW it's OK to use the high leg for 240V loads & a ? to the OP. How long has that panel been there? The NEC requires that the high leg be on the "B" phase in a panel, & that it be marked w/ orange tape, & a single pole breaker on the high leg is NOT permitted as a SP breaker is 120/240V rated & @208V it exceeds the rating of the breaker.

[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.

http://www.waterfront-woods.com/tempgraphics/SystemTypes-lo.jpg

[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. :o

[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.
183968

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. :mad:

[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;

184004

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.
183968Not 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. :eek:

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).

[Phil Metzger]

You technically do not have a problem to correct although I have never seen delta 3 phase in a residential setting. Delta is gradually being phased out but it is used in industrial settings to supply motor loads. So there is technically nothing wrong with your setup as long as your motors and breakers (very expensive)are rated for the voltage. In factories 120v circuits are often for lighting and delta which should be (b phase) is used for 3 phase motor loads. Other than that delta is not used. Your panel does show that it is a delta panel, but they also make special panels that only have a and c phase at the top ( in your case a and b) for the first 20 or so circuits then standard busses at the bottom. Let me know if you have any more questions. Can't believe the power company let you have 3 phase in your house though.

[Anthony Whitesell]

P.S. Square D QO is also for use and is used in residences. All the people that I know that I have looked at their electrical have them, including me. Though it is rated for use in more robust situations (commercial, industrial). Square D has a Homelite series which is only for residential use.

[Ruhi Arslan]

You technically do not have a problem to correct ...

Wow Phil... It took you three years to make the first post. I feel privileged. :D

I have learned a bit more than I should about this whole thing but I really appreciate all the input by the way. My conclusion is that I do not have anything technically wrong as long as the breakers on the "high-leg", which is C bus on my panel, are rated 240V. This is also indicated inside the panel. High-leg should have been B even according to the instructions affixed inside the panel cover but not a big issue. It's been inspected and approved - not necessarily means it is done correctly but not a "techical" issue. It is what it is.

http://www.sawmillcreek.org/attachment.php?attachmentid=183950&d=1298486273

"When used on a 240/120 VAC, 3 Phase, 4 wire delta system, teh center bus must be connected to the phase having the highest voltage to ground. All breakers connected to this bus must be rated 240 VAC." This sums it for me understanding better now what I didn't know before this thread started. I also found out that, again according to the instructions form the panel door, "the sum of breaker ratings connected to any one stab must not exceed 200A". I did the math and what I found out is disturbing: I have 320A on A, 295A on B and 145A on C legs. Unless I have take half for the double and 1/3 of the triple breakers for each leg. For example, I have oven on A-B with double pole 40A. I added 40 on A and 40 on B. Do I need to add 20 and 20? If so, my loads are 173A on A, 178A on B and 53 on C legs.

I am going to look into replacing this panel with 42 circuit retro panel still with 3Ph, 4 wire delta and will have plenty of 120 or 120/240 single phase breakers. I'll have a 120/240V single phase panel for the shop for the simplicity. If for one reason or another, I ended up getting a 3Ph machine, I'll have the option to pull a new line form the main panel. Here is an example panel that I can get to replace this one;
http://www.murraylighting.com/ProductDetails.asp?ProductCode=3BR4242B200

Or I leave this one alone, and have another 3Ph panel for the shop for future possibilities. I just need to find an electrician who would know what the heck this panel is. Since I now know what I've got, my BS radar would be on full range. If and when I find someone that I can trust, I'll proceed accordingly.

[Phil Metzger]

Wow Phil... It took you three years to make the first post. I feel privileged. :D
.

I know it is sad, but I haven't had a lot of chances for woodworking for a while and have been more of a lurker for much of the time.

If you plan on doing something with the panel or changing it I would Install two panels one for strictly 3 phase applications an one for 120/240v single phase. This could easily be accomplished by buying a smaller 200 amp 3 phase panel with feed through lugs. From the lugs you could feed something like a 42 circuit panel for normal applications. i.e you would just take the 120v to ground legs into the new panel creating essentially a single phase panel. Clearly labeling both panels would make this much safer for anyone who works with them in the future. By doing this you still keep 3 phase available but have it separate from normal house loads.

In regard to your load calculation each leg of a breaker is capable of pulling the rated amperage on the breaker but most breakers are never pulling their full nameplate rating. For example your stove would only pull 40 amps if you were using all burners and the oven at the same time. If you have an ammeter you can measure the true load on each individual leg, but I doubt you are exceeding 200 amp on each leg. Unless you have all electric heat and appliances and it is negative 20 degrees outside.

[Rick Christopherson]

I am going to look into replacing this panel with 42 circuit retro panel still with 3Ph, 4 wire delta and will have plenty of 120 or 120/240 single phase breakers. I'll have a 120/240V single phase panel for the shop for the simplicity. If for one reason or another, I ended up getting a 3Ph machine, I'll have the option to pull a new line form the main panel.I think this entire discussion is getting to the point of being too over-thought; from both questions and their answers. At this point, all you should be looking at is the merit of adding a single-phase versus 3-phase subpanel. There are too many distractions that have been needlessly added to this discussion.