demand factor for multifamily remote garage

[jimingram]

I have an existing set of ten garage stalls. They are part of a 70's vintage apartment complex. However, they are in one building in the driveway, remote from the apartment buildings. There is an exisiting 100 amp service in the end garage stall. The existing wiring appears to have been for outside security lighting. It has been improperly spliced into to provide power for added garage door openers.

The owner wants to know what it will take to bring this garage building up to code.

Code requires a GFI convenience outlet, a GFI protected outlet for the door opener, and a light controlled by a switch. The local inspector is requiring 1500 VA for the convenience outlet and 180 VA for the switched light. There is a mix of 1/3 and 1/2 HP door opener motors.

May the demand factor for dwelling units in Table 220.42 be used for the convenience outlet and lighting load? The load for the outside security lights will be at 125%. Our enlightened State Board of Electricity will allow me to submit my own demand factor for the door opener motors. FAQ. How do you get away with that? Answer. They may accept my calcultions, but if it doesn't work I'm still responsible to fix it.

I'm looking forward to your comments.

Jim Ingram

 

[ActionDave]

So you have 100 amp service for what will most likely never amount to more than 40 amps of actual usage, unless all ten stalls decide to use a block heater and a space heater . I think you are fine

 

[iMuse97]

So you have 100 amp service for what will most likely never amount to more than 40 amps of actual usage, unless all ten stalls decide to use a block heater and a space heater . I think you are fine

As Dave says, you don't know what people will do with the convenience outlet, but all possible loads on this except continuous ones, would presumably be subject to a demand factor such as you suggest. Even block heaters and space heaters cycle on and off. What about chargers for hybrid cars? I know nothing about them...

 

[Smart $]

...

I'm looking forward to your comments.

Jim Ingram

You didn't say whether you need 10 of each, but assuming such...

(1500 + 180 ? 125%) ? 10 = 17.2kVA

100A ? 240V = 24kVA

24 - 17.2 = 6.8kVA

...or 56.7A at 120V left to work your opener demand into.