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How would I describe this? First, it's a mess. Arch flashed bus tabs, loose breakers, masthead falling off building, etc.

I'm not sure of voltage and amperage.

Not sure how to read the meter.

3/0 copper supplying a 3 phase load center.

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Tom's right. You gotta measure the voltage. It's probably either 120/240 three phase or 120/208 three phase. 120/208 is common for apartments and condos. 120/240 is more common for industrial where there's some 120/240 single phase loads but mostly heavy 3 phase loads like motors,heaters, etc.

The meter won't tell you.

Use the main breaker size for amperage unless it's more than the ampacity of the service conductors. The ampacity of the service conductors can be found in Table 310.15. You need both the size (3/0) and the type (THHN, THHW, etc).

Marc

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How do you two propose he measure the voltage? Between any two legs it is 208 volts. Between any leg and neutral it is 120 volts. Each leg can safely carry 100 amps. Now describe that, and that is what you got.

With a voltage meter at the top of the main breaker or did I misunderstand the question?

A 120/240 configuration has 240 v between any two lines. One secondary winding is center-tapped to make a neutral. So, this configuration has two lines that measure 120V to neutral and the 3rd line is 208V to neutral.

Like I said, this configuration isn't common in apartments and condos.

I don't know what type of facility Kurt is referring to.

Marc

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  • 1 month later...

That's what I figured. Thanks for the confirm. Lacking any pointers or rating plates, I didn't know if the meter had something to do with it.

Just as a point of interest, the sticker that's been placed over the meter obscures the "CL200" at the lower left side.

You could also tell that it's a 200-amp meter by the "TA30" designation, which indicates that the meter was calibrated at 30 amps (Test Amps), which is the calibration level for a 200-amp meter.

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