3 Phase comments please

Did a recent inspection that appeared to have 3 Phase electric service/panel. I don’t see this type of install very often and don’t know much about 3 Phase. I didn’t see much wrong with the service feeds themselves, but was wondering what I can tell my client about the 3 Phase service, i.e. advantages/disadvantages. The home had electric baseboard heat (also very unusual in this area), and I assume the electric draw has a lot to with the reason it has a 3 phase service. Any comments would be appreciated.

I would guess that it’s a 3 phase, 208Y/120 volt service. (A digital multi-meter could easily confirm this). There are some minor problems and looks a little sloppy but from the photos’ it doesn’t appear that there is anything dangerous. What do you want to know about 3 phase systems?

What are the advantages/disadvantages if any in a single family residential dwelling, does it save on electric cost, what would be the purpose it was used in the first place?

Very colorful. Looks like candy cane.

Did they have a large work shope with 3-phase equipment or a kiln?


Three phase when used is better from a economic standpoint and more efficient.
But that is only if their are motors running taking advantage of it.

There really is little advantage for a residential dwelling. The big disadvantage is that most residential equipment is designed to operate on 240 volts. That means that any electrical heating appliances listed at 240 volts and operating at 208 volts would have a significantly lower power output.

[INDENT]One advantage is you have 3 buss bars suppling 3 = 200 amp legs,instead of single phase only suppling 2 - 200 amp bus bars.More available wattage.More power.

Here your monthly minimum is so great with three phase , that you would still end with the same maybe even hire bill per month .:):smiley:

Some years ago, HVAC systems above a certain size were only available in 3-phase models. Consequently, I sometimes see a 3-phase service in larger, medium-aged homes. I don’t know of any reason someone would request (or the power company would agree to install) a 3-phase service unless the home’s equipment required it. However, once installed, it is usually not practical to change it even if the equipment that required it has been replaced or removed.

More importantly…is this a Zinsco panel? (Breaker handles kind of look like Zinsco’s)

Did Zinsco make 3 phase equipment? Looks like GE or Murray to me.

The blade type bus bars are what you want to look for:


It was a Murray panel per the label. I thought the same thing about the breakers and even questioned it in one of my other posts.