< memory book = open >
Just a quick response to George's post:
I used to have a contractor friend of mine who would not install a single phase breaker in a three phase panel and he would install two panels- One for single phase loads and one for 3 Phase loads when he dealt with a Delta 240/120 3 phase service.
When I was very green in the field, having starry eyed dreams of being an EEE-Lecktrickle Injun-ear (and really not seeing the connected craziness that comes with the job,... but that's another story ~:-O...), every new and existing power system was a beautiful lesson at hand.
In the more designated Industrial areas (as opposed to Commercial/light Industrial) - such as Gardena, Santa Fe Springs, and the portion of East LA known as "Bandini" (remember "Bandini Mountain"?), Delta systems covered the earth.
Many 3 Wire Deltas, and a large 1Ø 3 Wire system used for multiple Customers.
Where convenient or economical, customers were serviced with 4 Wire 240/120VAC 3Ø 4 Wire systems - typically warehouses and low demand machine shops.
The thing I found to be extremely bright, was the use of 1Ø 3 Wire Panelboards where L-N or smaller L-L single phase loads where connected, and 3Ø 3 Wire Panelboards (fed without the Grounded Neutral Conductor) where the heavier L-L loads (and, of course, the 3 phase loads) would be connected.
Made complete sense to me, and thought it was like a "standard" technique done by eee-lecktrikle injunears (sorry, I just can't stop jokingly mis-spelling the word "Electrical Engineer").
Not cost effective I agree but this was his standard and I'm not to sure he was wrong. He's gone to his reward now but I always knew why he installed things this way and he never would change.
Never got any straight answer myself, if this was "Bad Practice" or not - as even though it made 100% sense to me, it still may have been a poor choice somehow.
That was circa 1984 to 1987, and by the beginning of 1988 I was taking on the first (of what turned out to be many) Design/Build Projects - as the King Dingdong in charge of creating the Electrical Power and Lighting systems + generating the Construction Documents (drawing the plans).
When any 4 wire delta systems were encountered, I took the "Old School Approach" so commonly seen, and designed using the "1 Phase / 3 Phase" Panelboards concept.
Never had any issues with Plans Examiners or Inspectors (had many complimenting the idea as "Thinking Outside The Box").
So far, after searching the NEC, querying the ideas to building departments + inspectors, and asking a few "open minded EEs" (explained later), all signs point towards "Good and Ethical Design Practice".
Currently - and maybe as long as 10 years current, a 4 Wire Delta is rarely seen, let alone being involved with one of my designed projects.
What seemed to be so "normal" back then, is more or less nostalgic, and in a way - legendary stuff, when looked at in the field today.
Just felt really compelled to mention this after seeing George's reply, as just recently I was describing these very same things to field personnel - those of which were in Elementary School at the time I was first starting to perform designs involving the 4 wire delta systems.
< memory book = closed >
Scott35
btw:
"open minded EEs"
Referring to those EEE-Lecktrikkle Injun-ears, who refused to place themselves in Ivory Towers, and kept their minds open to remember how things in the field went; - like remembering the simple fact of how rapidly smoke is lost from equipment, intended to be connected to a 120V circuit, when it's connected to a circuit having a potential in the 185 - 215 Volts range!
Most had Trade Knowledge (worked as Electricians before going the EE route), a few didn't - all had excellent skills, nonetheless.
Rant is over