I am a commercial real estate appraiser and I oftentimes need to be specific about the electrical service available within a building. I can read the service panel(s) and total the various amps volts, but I don't know what is relevant to report. For example, I recently inspected a very large industrial building and all of the service panels combined had a total of 30,000 amp, and I also noted that it had a 3-phase unit. Is that relevant to report that is was 30,000 amp, 3-phase service? Should I also report the voltage? Should it read: 30,000 amp/### volt 3-phase service. In the future, can I just read the service panel(s) and total the numbers? Just because a panel says 4000 amps, does that mean it actually has 4000, or that it can handle that many amps?I know that's allot of questions, but any help that I can get would be helpful. Thanks!
You would be better off to hire an electrician to get this info as there are a lot of variables. The voltages and phases available, the amps available, and the number of circuits in each one. Many panels you have to remove the cover to see the rating, and this is dangerous. A typical building may have thirty 225 amp 3 ph. lighting panels that are fed off of 60 amp circuits for 277 vac lighting. The service may only be 800 amps for the whole building. This is very common and meets NEC requirements. The largest bldg. where I work at the Univ. is 400k sq ft and has a 4000 amp service at the 480 volt level. This is the same as 145 amps at the 13.2 kv level. It all depends on whether or not you own the high voltage service also. An industrial bldg. could be much more.
I believe that the sum of the individual service panels can exceed the service capacity of the building just as the sum of the individual circuit breakers in a panel can exceed the capacity of the panel. It is allowable to assume that not every load will be using power at the same time. Near the meter, there should be a master circuit breaker or set of fuses that determine the ampere rating of the service to the building. In a large industrial facility, that location may accessible only to qualified personnel, and you may need to ask a qualified person to give you a description. You should state the voltage, number of phases and current or KVA available at the meter location. For a large facility, you may want to itemize the ratings of panels serving major spaces and/or verify that all major spaces have the same voltage and number of phases available. For large industrial facilities, you should also determine if the utility or the customer owns major outdoor electrical equipment that is on the property.
