Residential Electrical Load calculation NEC

[Electriman]

Greetings,

When we size electrical service for a residential application, I use 220.82. Based on that the lighting and receptacles loads are factored at 40% when they are larger than 10 kVA.

But I do have also panel schedule spread sheets that consider lighting at 125% and receptacle at 100% of 90VA per each outlet.

During odd situations where we have so many receptacles in a property, then the feeder size gained from panel schedule spread sheets will be greater than what is gained from 220.82.

Now, the inspector is questioning me about that. He is saying that I need to size my feeder based on the spread sheet not based on the 220.82. Any recommendation how to respond?

Thank you in advance

 

[ptonsparky]

Who gives you the panel schedules? Ask them how they came about 125 and 100 percent for a residence. Bonkers. IMO.
Ask for the NEC article that says you must use those numbers?

 

[Fred B]

Your installation a dwelling unit or non-dwelling?
Panel Schedule spread sheet? Residential? 125% and 100% usually only considered in commercial or non-dwelling occupancies 220.42.

 

[ptonsparky]

Your installation a dwelling unit or non-dwelling?
Panel Schedule spread sheet? Residential? 125% and 100% usually only considered in commercial or non-dwelling occupancies 220.42.

Sounds like an Architect or Engineer that is new to residential.

 

[Birken Vogt]

Residential general load is based on square footage, regardless of how many lights and outlets are actually installed. Good thing too, or we would be installing 600 amp services with all the outlets required in the NEC these days.

 

[wwhitney]

During odd situations where we have so many receptacles in a property, then the feeder size gained from panel schedule spread sheets will be greater than what is gained from 220.82.

220.82 applies only to the service or feeder supplying the total connected load of the dwelling unit, so you can't apportion the 220.82 load when calculating feeder sizes for a subset of the loads, you need to use Article 220 Part III.

However, it is possible that the Article 220 Part III calculation for a subset of the loads is greater than the 220.82 for the total connected load. In that case, you can size the feeder for the subset the same as the feeder/service for the total connected load, per 310.12(C).

Cheers, Wayne

 

[jaggedben]

What Wayne said.

Also don't show the inspector the panel schedules. Nobody does that for resi.

 

[Knightryder12]

When we design residential spaces, we have a panel schedule that has no load indicated, its just so the contractor has a circuit number for that area. We put a note on that schedule that refers the plan reviewer and inspector to refer to the load calculations for the panel and the service.