Load Calcs on Existing Distribution System

[kWatt767]

We have a small job in the office (on a large existing building) that calls for a very simple face lift in a circulation area of a university building. We are essentially demo'ing 3 existing 100W incandescent luminaires and a few outlets, and then adding 3 LED can lights and a few new outlets. My coworker is stressed about having to prove the load on the distribution system all the way back to the point of service, as we do not have good information on the calculated or demand load in order to perform a comprehensive load calculation, nor do we have the time for the 30 day metering. So here's my question:

I seem to recall an exemption in the code that states that if the new load on the branch panelboard does not exceed more than 5% of the panel's bus rating, that load calculations for feeders and equipment up-stream of that panel are not required. Is this correct, or some bad information I received early on from my early mentors? I can't seem to find this anywhere in the code (NEC2014). Any insight would be appreciated.

Thanks,

kW

 

[Smart $]

There's no such exemption.

So what is the calculated load of what's being demo'd vs. what you are adding. If less or relatively close, I wouldn't worry about it unless the AHJ requires a calculation.

 

[jglavin427]

Most AHJs should have an official policy, for example in my AHJ you can add one 20-amp, single-pole branch circuit without load calculations and anything beyond that requires an engineered drawing.

When doing load calcs in a high-rise or other large building, we usually prove the panels we are working on as well as the panels feeding those. Load calcs for distribution beyond that point are not typically needed unless its a major change of use in the building. This is typically sufficient for the local AHJs as long as the calcs are signed by a PE.

 

[petersonra]

You are just replacing existing fixtures and outlets. I don't see that any load calculation is required at all.

There is no requirement that you investigate existing work to insure that it meets code.

 

[Smart $]

You are just replacing existing fixtures and outlets. I don't see that any load calculation is required at all.

There is no requirement that you investigate existing work to insure that it meets code.

Tread lightly there. A lot of people refer or take 'outlet' to mean GP receptacle. Code does not.

 

[electrofelon]

We have a small job in the office (on a large existing building) that calls for a very simple face lift in a circulation area of a university building. We are essentially demo'ing 3 existing 100W incandescent luminaires and a few outlets, and then adding 3 LED can lights and a few new outlets. My coworker is stressed about having to prove the load on the distribution system all the way back to the point of service, as we do not have good information on the calculated or demand load in order to perform a comprehensive load calculation, nor do we have the time for the 30 day metering. So here's my question:

I seem to recall an exemption in the code that states that if the new load on the branch panelboard does not exceed more than 5% of the panel's bus rating, that load calculations for feeders and equipment up-stream of that panel are not required. Is this correct, or some bad information I received early on from my early mentors? I can't seem to find this anywhere in the code (NEC2014). Any insight would be appreciated.

Thanks,

kW

FWIW, in all the jurisdictions i work in, doing load calcs for the scope of work you described would never even cross my mind