yes i meant 120/208/120 is my 240 situation . I have a 200 amp 3phase setup now. The power is turned off I cant test the voltage . he says its 120/ 208w 3phase 4wire. im upgrading to 600 amp for the owner of the building . He wants to be able to attract more clients with 2 subpanels available for heavy equipment. My concern is that the 208 3phase will be a deterrent for company's that have 240v equipment. Of course I have the problem of not being able to give a specific load as there is no tenant yet. I have made up calculations based on common machines to submit the one line to the power company.
I'm sorry if this sounds condescending, I'm not trying to be, I'm trying to help by educating. But I think it's important as an electrical professional for you to get used to describing power systems in the same convention as everyone else so as to avoid the kind of confusion created in the beginning of this post. When you describe a 3 phase power system, you should always describe it in terms of the Line to Line voltage first, followed by the Line to Neutral voltage (if any), and NEVER with the Line to Ground voltage, because that can be deceiving.
So I believe, as others have said, that what you are describing as "120-120-208" or even "120-208-120" is in fact, 240/120V 3 phase 4 wire, where the Line to Line voltage is 240 delta (on all three phases), the Line to Neutral is 120 on A and C, and that's it. You NEVER describe the Line to Ground voltage because it is not a legitimate connection that can be used. In the case of a 240/120 3Ph 4W transformer, the B phase to ground will usually measure 208V, but again, that is just an interesting side note, you are not permitted to use that connection for anything.
Unfortunately because 208Y/120 3Ph4W is another legit voltage class, you describing yours as 120-208-120 is only going to continue the confusion.
Re-240V equipment with a 208V feed: as others have said, MOST equipment is fine with it, i.e. motors, because the NEMA design specs are for +- 10% of nominal, which you will find is usually 230V, not 240V*. So 230 x .9 = 207V, marginally OK. When you see a motor that is labeled "208-230V", then that usually means that is was designed as 220V, because 220-10% is 198V and 220+10% = 242V, so it's a good compromise. Heaters will just take longer (less heat) and most things with power supplies have a very wide voltage tolerance.
* 240V is what's called the "Distribution Voltage", 230V is called the "Utilization Voltage". It's that way all around: 460V vs 480V, 115V vs 120V etc. etc.
