cctalk Digest, Vol 88, Issue 2

That's correct. A to C is also valid, presumably it's rotated if there's a lot of open delta in an area (again, why?) to balance phases. Right, and you get a mostly unusable "high leg" w.r.t. neutral, usually 208V though I don't know what it ends up actually being in open delta with poor/uneven loading. The 120/240 power available is also supposed to be derated, IIRC it's only supposed to be 5-10% of total service load. High-leg delta exists so you can have 120/240 lighting and appliance loads in a building that consumes mostly 3-phase, like a machine shop with an office. In most areas you aren't allowed to have more than one type of service to a building (not sure if that's true for double-fed sites, never seen one with two kinds though). I've heard the Power Company usually doesn't want to install high-leg delta anymore for a variety of reasons: the load limit, people not understanding they need to skip a breaker, 120/208Y having become the usual form of smaller service three phase, etc. Right, there's one or two of those services in town here for a couple of small commercial buildings. Four wire high leg open delta off the pole, two transformers on the pole. Thanks, Jonathan