220.84 Optional multifamily dwelling calc

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flick

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When doing the calculations for multifamily dwellings using the optional method, I come up with a lower service load than using the standard part III calculations, as is normal.

However, 220.84 (C)(3) states to use the nameplate rating of ranges for the optional method which obviously eliminates the standard 8kW used in part III table 220.55.

I do not have the actual nameplate rating of these ranges. Is there a substitute value that is generally accepted for a standard range? The typical ranges I've seen are rated around 10.5 to 11.8 kW.

I'm in the pre-bid process on upgrading two apartment building services. Would it be safe to use 11.8 or 12kW in these calculations? I am allowing for an electric range in each of 9 apartments in one building, even though only about half have electric ranges. I felt it would be better to plan on electric ranges (this is an existing, older building, with tenants) even though they are not present in all apartments at this time.

I need to come up with a tentative plan to present to the building dept. for approval before I go any further.

Any thoughts?


Thanks,

John
 
John, you've done a standard calculation and come up with 428A for this service, right? So, I'm guessing you're proceeding with the optional method in hopes of getting less than 400A, then?

FWIW, a 400A service is pretty light for an 8-plex, IMO. Don't you think it would be a better design to provide for future expansion with a full 500A service? Just thinking out loud, you've seen the place and I haven't. :)

flick said:
I do not have the actual nameplate rating of these ranges. Is there a substitute value that is generally accepted for a standard range?
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I'd ask for the actual size from the owner. They bust into their tenant's units all the time anyway for stupid things (been there), this would be a small visit. :)

In lieu of that, I'd say an 12 kW guess would more than cover the actual ranges in the units.
 
georgestolz said:
Residential Journeyman, Commercial Apprentice, and All-Around Hack that is quietly waiting for the snappy one-liner signature fad to pass - Anyway, this guy walks into a pub with an ostrich and a cat in tow. The bartender looks at the group and says, "What will it be?" The man says, "I'll have a pint." The ostrich says, "I'll have a pint." The cat says, "I'll take a pint and a shot of whiskey, and I ain't bloody paying!" So, the....
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More, please!
 
georgestolz said:
I'd ask for the actual size from the owner. They bust into their tenant's units all the time anyway for stupid things (been there), this would be a small visit. :)
Click to expand...
In rentals, the actual size today will not be the actual size next week. It makes getting today's actual nameplate data less important. Plus, the landlord's going to think you're a goof, wanting to get in to read stuff off a range. "It's a stove, same as any other", is what he'll be thinking to himself in his head. I'd just as soon not risk whatever credibility I might have during that sales call. When a range craps out in a rental, landlords often (and typically) purchase whatever is on sale at the local home center. Using some sort of average (even if it's a tad on the high side) might be more advisable. I use about 11-1/2 kw for this purpose, particularly if I see only 40 and 50 amp OCPD's for the existing ranges. Naturally, if this is a high-end apartment house, all bets are off, and you really need to look around the places.
 
Well, this is a low end apartment house. It's probably 40 years old or better, and not in a good neighborhood, so there's no reason to believe that this apartment building will ever be anything but low end. The apartments in question are really what I would consider efficiency apartments. 6100' square, 9 apartments, 678' square each unit, more or less.

George, you're right that I did the standard calcs already and came up with 428A. The optional gives me a little less than 400. I consider 428A
conservative because of the baseboard heating at 10W per square foot being a conservative number and that not all units have electric ranges at this time, and may never have.

I still need to add the house loads in, but they are small. I'll probably go with 11.5kW and see what the Bldg. Dept. has to say.

Thanks for the replies.


John
 
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