Fun with three-phase at home
Friday I went through a house inspection for a property that we made an offer on. It turns out that the house has three-phase power. I have some other resources to tap, but, based on past experience, there are some creative people posting here and I would like to take advantage of that head-scratching ability.
I want to ask about a couple of things that came to mind this morning. Will the three-phase complicate installation of two things that I will probably consider, a backup generator and a net-metered photovoltaic system? Some details are below in case it makes any difference.
I have an additional question about the grounds in the panels. Rather than being hooked to the buss bars, the grounds are neatly wound in a spiral. Why would that have been done?
The house is an 80-yo, 2000 sq foot frame, raised building with a large separate two-car garage with a shop in the back and a generous attic. There are additions to the original house structure.
There are two panels that are the same size as a typical 200-amp, full-sized service panel. The meter pan conduit goes into a junction box that is probably 6 x 8 in. and both, flanking, panels are connected to that by conduit. I did not get a chance to examine the splices in the large junction box in detail.
One panel is a mix if three phase and single-phase circuits and the other is all single phase. That's right, THREE PHASE. There are lots of breakers including some half-width despite the fact that there are two big panels for a not so large house. (I must be drawn to houses that are wired for three phases. My home that got Katrinad was a 1950 house that was originally wired for three-phase.) The garage has a single-phase sub panel. The consensus at the time three of us were looking at it was that a third leg was there, but disconnected. Since it looks like a single-phase subpanel, I am now thinking he installed is as single phase, but included enough conductors to make it three phase in case he ever wanted to upgrade to run ... what? We saw one bit if evidence that there was knob and tube wiring in ancient times. It was an insulator with some (disconnected) wire attached near the apex of a roof gable.
Unfortunately I did not get to stare in the boxes for very long. The termite and video plumbing inspectors there at the same time so I was pretty darned busy.
Here is the source of my second question. Grounds for individual circuits in both the big panels are neatly wrapped together in a big spiral and they look like they are connected to the boxes rather than to the buss bar. There are lots of screws available on the bars so I don't understand that. It is clearly not supposed to be done that way.
Upon further reflection maybe it was done because the circuits were upgraded to grounded BEFORE an older, fused service panel was replaced with the circuit-breaker service panels. When it came time to switch to breaker panels, he just stuffed the bundled ground wires into the new box not bothering to hook them to the buss bar. That would have taken some serious additional time.
BTW, the former owner is a now-deceased electrical contractor that had been in business by himself for what appears to have been a working lifetime.