Demand Factor for Non-Dwelling Receptacle Loads using Existing Receptacles

[32Lateralus]

Let's say I have an existing facility, and we are doing some new work there.

We have solid as-builts with calculated loads. We could do a 30-day meter study and apply 125% but time doesnt really allow.

Ive often seen calcs done where it just takes the bulk panel as-built load, maybe some removed load, and then calcs all the new load separately with it's own stand-alone demand factors not accounting for existing (the more conservative approach it seems) and adds it to the calculated as-built load. But are we able to group existing loads into our demand factors?

For example:
Lets assume a 100A panel, 70A calculated load. The as-builts show over 10KVA of receptacle load and some existing remainder at 50%. When I add new receptacle load, and I able to take it at 50% as well? Same for adding a motor that isnt the largest compared to existing. Am I able to use these demand factors from existing loads in my calc?

 

[Npstewart]

Yes. Forget that its "Existing" and total up the entire receptacle load, subtract 10kW and the remainder at 50% and add back in the 10kW If you do this, then you dont need to consider the 125% because the 125% is only if you're using one of the cited methods for existing loads via 30 day load study or 1 year demand.

The NEC doesn't really make many references to "Existing", just treat it like a new service calculation and total up all of the existing + new loads.


FYI: You dont need to wait 30 days if the building has a demand meter. Just call the power company and ask for the peak kWD or have the owner do it if they wont give it to you.