Existing Panel

[EverydayElectrician]

Hi there, I am new to the Forum, so if this subject has been brought up before, forgive me.

I have an existing panel that I am adding a bunch of circuits to. The panel serves a office/lab area and just looking at the breakers, doesn't have alot of load on it.

How would I verify that the circuits I want to add are within the capacity of the current panel?

 

[charlie b]

220.87 has a method that involves measuring existing load for 30 days.

 

[EverydayElectrician]

charllie b,

Thanks for the suggestion. I saw the formula you mentioned, but was hoping there was another alternative that wasn't so involved.
the job changed anyways so now I'm just coming out of a different panel.

Out of curiosity, has anyone else ever had to do load calculations to prove a panel had the capacity for the circuits you were installing?

 

[LarryFine]

Out of curiosity, has anyone else ever had to do load calculations to prove a panel had the capacity for the circuits you were installing?

All the time.

 

[ptonsparky]

Out of curiosity, has anyone else ever had to do load calculations to prove a panel had the capacity for the circuits you were installing?

Never by an AHJ, but Yes to satisfy my own curiosity.

 

[Dennis Alwon]

Very rarely on resi work. I can eyeball the situation and pretty much know if it will work or not. On occasion I have had to do a calc.

 

[kingpb]

Working with one panel should be easy enough to do a load survey as if it's new and do the calc in lieu of 30 days of measurement.

 

[petersonra]

if the load is too much, one or more breakers will trip. the end user will not like that.

having said that, the load calculations in the code are very conservative. most cases you will rarely see 50% of the load that it calculates.

 

[EverydayElectrician]

Thanks for the all the input!