Hey Brad, grab it.
When I mentioned that typical small generators sold in say Menards or Lowes aren't setup for 3 phase, I was going to mention military generators that are setup to do either single or three phase. When I was in the Army, we had a wide variety of gen sets that were capable of doing both, starting with the 10K gasoline sets, and of course our 15K, 30K, and 60K diesel sets did as well...single phase were L1 and L2 to nuetral for 110, or 220 across L1 and L2. That is all that you will need for residential. That will get you 110, 110, 220 single phase. L3 and L4 in conjunction with L1 and L2 will get you three phase across L1 and L2, L2 and L3, and L3 and L4...which you will not need.
My mistake Brad. I thought that you were talking about motors and commercial grade appliances. If I had known that you were looking at a 15K military Gen set, probably diesel, I would have told you to jump all over it and here is why. Those old diesel military gen sets needed to run somewhere between 60 and 80 percent draw to keep from tearing them up, which meant that we had to tie in load banks across the loads. In tactical maintenance, which I was, we generally used 30K and 60K gen sets because we at times had that much stuff hooked up to them, but at times not...and on the latter occasions, may have fired up huge gen sets in the field, and had only say like 10K draw on them of equipment shelters in being maintained. On those occasions, we would have to dial in the load banks across our coils to increase the draw to as I recall a minimum of 60 percent (36K) a typical maximum of 80 percent (48K) on a 60K gen set, or 18K to 24K on a 30K gen set.
Brad, from what you are saying as I understand it, you have the opportunity to purchase an old 15K military gen set, I assume diesel because thats what we used, and if that;s the case and its in good shape, jump all over it. With a 15K,you won't have to worry about a load bank to make up the difference in load draw, and those old Continental diesels ran a real consistent speed once you dialed them up to the correct speed (cycles/hertz) and locked the dial in. Whereas the smaller 10K gasoline units used governors that had tendencies to float nominal speeds all over the place, which gen sets are known for, dirty power. With our diesels, we would dial them in, walk away and come back in an hour after the engines were warmed up, fine tune the speeds, relock the dials, and they would run error free all day and night. Out in the field, we always rotated two gen sets. One day one, next day the other, and so on.
Brad, you have a chance to buy and old diesel 15K in good shape? Grab it. It will do single and three phase, will give you 110, 110, 220 single phase. Grab it, grab it, grab it...or I will. You won't find anything out on the market new that will keep up with it without paying mega $$$. Grab it.
Good luck Brad.