Determine existing load capacity

[Jester07]

Is there a quick format to determine if an existing load center, panelboard, MCC, or transformer has the capacity to add new loads? We have one-line diagrams available, but we do not have load metering for each panel or bus duct. In our industrial environment we typically rate the loads as 'continuous'.

In short, how do we know if we can add another panel or pump to an existing main panel?

 

[charlie b]

If you can't tell the existing loading using a list of all connected equipment, then I think you are stuck with measuring the load on the affected panels for 30 days. Add 25% to the highest measured demand (in units of KW, not KW-HR). The difference between that number and the panel's rating (or the rating of the panel's feeder and OCPD) gives you the amount of load you can safely add to that panel.

 

[cowboyjwc]

We used to have to do exactly what Charlie said. By the time we got all of the information necessary to get the answer, it probably would have taken us 30 days anyways.

It will also let you know when your peak loads are (if that information is useful to you) so that you can trim off loads if you need to. We found out (not that we shouldn't have thought about it) that the reason we were tripping breakers is that the whole plant, lights and equipment, was trying to come up at the same time. We found that by staggering the on times of areas by just a few minutes eliminated that problem.