I recently upgraded 4 of 6 apartments in Oakland, the existing tenant is complaining that her lighting is dimming, caused by the "additional load", I changed the 30amp 120volt fuse panels, for each apt. with 240v 60amp panels and changed the 40 amp single pole breakers(2pole with only A phase connected)in recently "upgraded" meter pack to connect the units to both phases, to include the unused phase, the main disconnect has 200 amp fuses. the entire square footage and calcs only comes to 175 amps. and i'll have to check but I believe the guy put in 4/0 copper service conductors....correct me if I'm missing something but I cant see how upgrading the other four apt. would have any effect on one of the existing ones that has not been improved? chris

"I believe the guy put in 4/0 copper service conductors...." If you You mean PG&E then they usually install 4/0 Aluminum for underground service.
It could be a loose connection at the service point or in the service equipment.

is it one tenant that is having dimming lights or others are having the same problem?

It could also be that when a motor load turns on the lights dim, and probably it has been the case all along but she just started to notice it.

Does the apartment have elevators?

I would recommend you visually confirm the dimming and then install a recording meter and check for high and low voltage reading.

i am sure others will give you pointers as well.

from the records the service was upgraded around 1987 by ampm electric, but connecting all on one phase was what surprised me, I didnt see any thing that looked bad though, I'll check the connections, its a OH 3 inch riser, 400 amp fpe disco, which looks well designed surprisingly, chris

so I checked the main disco and there is slight corrosion on the lug for one phase, not the neutral as i thought might be the case, and each apt calc.s at 35 amps 240v. the complaining unit is still on a 40amp breaker. there is a sump pump on the new house panel and there are number 2/0 wire feeding two stacks of 3 and four meters from a hot gutter split bolted to 4/0 copper. my question is would I connect the recoding meter to the effected unit feeders or the main service wires.? this is the first time i've done a multi unit upgrade. thanks chris

Oh normal feed in voltage is 245volts daytime, C

I'll bet when you upgrade that remaining 120V/40A feeder and panel like you did with the others using both sides of the single-phase, the voltage drop problem in that unit will disappear.

Agreed, They only really noticed because they saw your truck there.