Happy Holidays, all!

What do you all do when the Utility's design letter/AFC calculations contain info you know is incorrect? What is our responsibility to the Utility in such cases?

On my most current project, the Utility's stated incoming conductor information is incorrect, both in quantity of conductors and size(8 parallel 750mcm vs 4 parallel 350mcm). I know because I have photo documentation of what's landed on the utility side of the gear. This happens somewhat regularly.

Obviously I want my study to be accurate, so I'm going to model the incoming as the Utility states it and make sure the AFC matches, then see how different the AFC will be with the actual installed conductors.

If, in this case, the AFC was close, would you send a courtesy note to the Utility to let them know their info is incorrect? Do we have a responsibility to do so? If the AFC was significantly different using the installed conductors, does the courtesy become a responsibility?

Nobody? Is this taboo territory?

Happens once in awhile. Very recently again for me. I'll try to upload a heavily redacted version of the conversation. I just stay after them until they comply or tell me it isn't possible or it is clear it is a lost cause.

That's a difficult one. In a past life, I headed up the short circuit studies group for a large electric utility and we NEVER made mistakes (humor)

There are a few option, one is to use an iterative approach which I have discussed here before (and on the brainfiller.com website)
Begin with what you know (incorrect data) and run the study. Note the incident energy and PPE at each location.
Then begin to vary the suspect data. Number per phase, lengths etc. See how that affects the incident energy and PPE.
See if any of the alternative cases change the PPE requirements. Most notably, does the change in fault current, change a protective device's fault clearing time.
After running several alternate cases, this should provide you with a range of validity where the recommended PPE is sufficient.
State these assumptions in the report - i.e. PPE is based on... x,y,z
Not a perfect answer but often, sufficient data is lacking.

Also, yes - notify the electric utility as a CYA move. Just state something like, it was noticed that....

Good luck!

Also, as mentioned on here before a few times, I've resorted to sending the POCO a link to this video to get accurate information. It has worked every time so far:

https://www.youtube.com/watch?v=5TPIOAX6Ksk

Glad to see you participating on here, Jim. I think it's been awhile. At least to my short memory.

Thanks. 2025 was an insane year but nice to be back a bit more! Thank to you and everyone for keeping the conversation moving!

I like how at the end, they give you info without so much as acknowledging any of the previous conversation

Like in the Batman Lego movie, where he hits something with the batarang after missing it 15 times, and yells, "First try!"

Thank you! Only tangentially related, but I'm going in circles with a utility over a project I'm doing for the local water district. The district has a turbine in line with the local water line that generates power as it throttles the pressure. This power is stepped up from 480V to 12.4kV from a transformer on the property, and fed back into the grid. It's monitored by a utility-owned meter.

Neither the water district, nor the power utility has any record of owning the transformer, and the Utility has no information on the meter. I'm on my 3rd Utility rep, and as yet. no one has been able to identify this meter that they installed, which has an exclusive number belonging to the Utility, and is in operation.