Help me to identify my service panel for a subpanel work

[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.

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.



"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/Produc...de=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.
.

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.