service size for Medical Office Building

[mshields]

We recently renovated 42,000 square feet of a 50,000 square foot Medical Office Building. The service is 600A at 208Y/120V. The wiring inspector is asking that we provide a NEC compliant calculation which doesn't seem unreasonable. Yet I have a few questions:

- If this were an addition, we'd take the max kW demand for the past 2 years and use that as our base. Is that what should be done with renovation as well?

- Where in the code, is the above rule indicated. I don't see it in Article 220 nor in 230. Did I just miss it or is it elsewhere?

Thanks,

Mike

 

[roger]

See the exception in 220.87(1)

Roger

 

[Volta]

I would be leary of using the allowed determination of existing loads as more than 80% of the building has been renovated. So many loads have changed, both added and removed, that it would be difficult to accurately list all of the items.

I would suggest a full calc. if at all possible.

 

[Npstewart]

In my experience it isn't practical to do a load calc for the entire building on a usual basis.

I ask for the peak KWD over 12 months. Take that load at 125&, then my new load I take at 100%.

This has never failed me yet and I feel like its more accurate then a load calc.
.
However if you are renovating that much, the existing load wouldnt be good for anything, they are probably changing quite a bit including the AC, you should do a load calc no doubt about it.

 

[malachi constant]

With 80% of the footprint being remodeled it is probably not practical to use 220.87. I would do the following:
1. Perform a full load calc on the building. With 80% of the loads new this should be relatively easy. Calculate the new loads. Use your best estimates on existing loads that are being refed.
2. Compare with existing maximum demand data as a check.