Calculatng Existing Load For Panel

[TrickleCharge]

Ok so I have a project where they are adding an EV charging station and the original panel load was 124A on a 100A panel. When I sent the correction back the response I got from the contractor (who does solar) said "I am allowed to go 120% of the rating. I laughed under my breath and said that did not apply. Well anyways they submitted a new revised load calc that just so happens to come in at 99A, seems like they are just "making it work". They use a cheesy spreadsheat that calculates the circuits in amps. There are some receptacle loads, RTU, and a few other pieces of equipment on this panel (maybe 8 ckts). The EVCS draws 32A/Phase as shown on their panel schedule. Now because they are being difficult with providing accurate calcs that are "true" can I request them to meter this panel per 220.87? What do you guys think?

Thanks

 

[charlie b]

Yes you can. A spreadsheet that calculates loads in units of amps, where both single phase and three phase loads are connected to the panel, is very likely to have the wrong answer. I would not trust it unless I had a copy of the Excel file and checked the way it performs the math. I would also need to know how the calculation differentiates between continuous and non-continuous loads. If there are any continuous loads for which the spreadsheet did not add 25%, then the panel will be overloaded when you add the charging station.

 

[petersonra]

Ok so I have a project where they are adding an EV charging station and the original panel load was 124A on a 100A panel. When I sent the correction back the response I got from the contractor (who does solar) said "I am allowed to go 120% of the rating. I laughed under my breath and said that did not apply. Well anyways they submitted a new revised load calc that just so happens to come in at 99A, seems like they are just "making it work". They use a cheesy spreadsheat that calculates the circuits in amps. There are some receptacle loads, RTU, and a few other pieces of equipment on this panel (maybe 8 ckts). The EVCS draws 32A/Phase as shown on their panel schedule. Now because they are being difficult with providing accurate calcs that are "true" can I request them to meter this panel per 220.87? What do you guys think?

Thanks

You can request just about anything, whether you can make them do it is something entirely different.

How did the original calculated load end up at 124A on a 100A panel in the first place? That sounds like it might well have been done incorrectly.

I think you have to look at what they gave you and decide if it is correct or not and go from there.

 

[TrickleCharge]

Now in this case with one of the existing circuits being a 20A 2p Breaker for a RTU how would this factor in to a 30 day analysis being that it is winter and the A/C is not being used? I know there is some reference towards seasonal issues correct for heat and a/c?

 

[charlie b]

The process I use (as required by Washington codes) is as follows:

• Measure the peak demand over 15 minute periods for 30 days.
• Take the largest value measured during the 30 days, and add 25%.
• Multiply by a correction factor for each of the following considerations:
  • Time of year (this is the one you are asking about),
  • Occupancy (e.g., if only a small portion of the building has tenants, you should add something to the measured value),
  • Any other factor that might have influenced the measurement.
• Add the amount of load you intend to add.
• Compare this to the service size.