Store Building Service Sizing

[pdr]

Am calculating the Service size for multi-unit commercial building. Have 22 units, plus house panel with lighting and motor loads. May I use the same demand factors for General Lighting as defined in Annex D, Example D4(a) for Multifamily Dwelling? Example D3 Store Building, does not show calculations for Multi stores. Since the lighting demand factor allowance is different in commercial than residential, I need guidance in all the demand factors that apply to commercial units for retail space.

Thanks

 

[jtester]

Re: Store Building Service Sizing

pdr
You can't use the same demand factors for residential as for commercial. Look at Table 220.11. In general for stores, the demand factor is 100%. There are additional requirements for track lighting, store windows, etc.
I encourage you to progress carefully, and ask plenty of questions if you are unusre about anything. Better yet, if you can, find the help of someone experienced in this calculation.
Jim T

 

[pdr]

Re: Store Building Service Sizing

jtester
I have captured store windows, outside signs, and track lighting, general lighting, and receptacle loads (Table 220.3 - Office Bldgs - footnote "b") I used footnote "b" because I do not know the exact amount of receptacles. These units are all vacant now and being restored after hurricane damage. Understand use of Table 220.11, and all other requirements of Art. 220.

As I understand, I must total all loads (22 units) without any demand factor, except for as allowed by Table 220.13.

Thank you...pdr

 

[charlie b]

Re: Store Building Service Sizing

That is correct. In a multi-family residence (e.g., apartment building), it would be a good bet that not all families would be doing laundry, cooking, vacuuming, and running their dishwashers, all at the same time. That is why demand factors are available to us. But in a commercial building, there is no telling who will be running what, all at the same time. So we have to presume that everything will be running.

Receptacles are a slightly different thing. The code requires us to install plenty of receptacles. It is a good bet that no-one, anywhere, will have something plugged into every available receptacle. That is why Table 220.13 gives us a (albeit slight) break.