Need some help with this panel

Hi all,

This is from a condo today, built about 1970 but replaced panel at some point.

First off, no ground wires visible from any of the branch wiring.

And the main, 3 - 100 amp feeds?

Any thoughts and thanks in advance!

Looks like 3 phase to me
I never saw 3 phase in Residential only Commercial or industrial .
Looks like the feed is metal conduit Steel lock nut and plastic bushing that supplies a ground to the box.
I wonder is all the small lines going out are old BX if so they pick up the ground via a grnd strip and the connector .
I have not been in the trade since 1978 so many things are changed and I am a Canadian .
The green is grounds but can not see where they attach to the box .

Hi Roy, that’s what I was thinking too, but 3 phase in a condo?
All the outlets were grounded as they should be in a 1970 bldg.

Yes 3Ø panel. Not common but it is what it is. :slight_smile:

Thanks for the confirmation Robert, I wish I knew the reason for 3 phase in a condo.
All the HVAC is outside of the condo unit so not inspected.
I can imagine the HVAC could be 3 phase, so maybe that’s why?

Very strange for residential, however considering it is 3 phase did you by chance stick a meter on it to see if it is 208 or 480, I bet it is 208 setup

Roy and I were emailing and that was his guess as well, 208.
This was a 14 story condo building so for that scale it makes sense to use
such a set up.

I’ve just never seen it before so wanted to run it by everyone!

Thanks Thomas I am sure many learned much from your post

Thanks for helping think it through Roy!

I guess I should point out a couple advantages to using 3 phase.
One is that you can use much smaller wire gauges to convey the power, that lowers
installation costs.

Second, 3 phase motors cost less to build and are thus less expensive to purchase.

Third, 3 phase motors typically last much longer than single phase motors partly due to
the simpler construction and also that 3 phase electric is delivered in 3 offset phases.
The offset phases mean the power supply to the motor is very even and thus not as hard on the motor.

Whereas single phase power is more of an “on,off” cycle and wears motors out more quickly.