Need Help!

Status
Not open for further replies.

JoeNewJersey

New member
Hello folks.

Does 120/208V, 3 phase, 600 Amps sound correct for an old residence building with 30 apartments?

I have to quote a new service and I?ve just arrived to those numbers.

Am I doing right estimating 33 VA per square meter per apartment (about 120 m2 each)?

Thanks for your help.

Joe.-
 
Can you show your entire load calculation for us to verify? With only the square footage to work with, there's no way of knowing.

If the service is three-phase, have you adjusted your voltage accordingly (208V x 1.73 = 360V)?
 
360 is a short-cut multiplier / divisor for a 208y/120 volt system.


Roger
 
THERE ARE NO SHORTCUTS! I apologize for shouting, but why are electricians so opposed to performing an article 220 load calculation? There is not a "watts per square foot" shortcut to be used. Do the COMPLETE claculation and you will KNOW what the load will be and may then determine the service that should be installed, anything else is just a guess. Guessing is not an NEC compliant activity.
 
Haskindm, slow down, explain to me what the difference (besides less than 1/100th of an amp) is in the two calculations below.

10,000 / 208 / 1.732 = 27.76
10,000 / 360 = 27.77

The term "short-cut" here doesn't mean an electrician is opposed to performing a calculation, it is simply taking out unnecessary moves in the calculation process.

Roger
 
Roger,
I do not mean the shortcut of rounding to 360 for 3-phase 208, I am talking about the "shortcut" by the OP of attempting to estimate a service load based on the square footage of the building. A complete article 220 calculation which considers the heating, cooling, appliances and other variables is not that difficult to do, yet many "electricians" try to avoid doing it.
This type of question shows up on the forum almost weekly. Article 220 is in the NEC so that we do not need to guess at loads. I advocate that it be used and not avoided.
In Maryland you must perform an article 220 calculation as part of the Master Electrician exam, and I assume the same is true elsewhere. There are examples to follow in NEC Annex D. This is a tool that is available to use, so use it!
 
Haskindm, my apologies, I see where you are coming from and I whole heartedly agee.

Roger
 
JoeNewJersey said:
Hello folks.

Does 120/208V, 3 phase, 600 Amps sound correct for an old residence building with 30 apartments?

I have to quote a new service and I?ve just arrived to those numbers.

Am I doing right estimating 33 VA per square meter per apartment (about 120 m2 each)?

Thanks for your help.

Joe.-

My experience with this is that the AHJ will want to see a load calc.

I "tried" to squeak an existing 150A service in a 2 to 3 unit renov...AHJ said I'll allow it IF you can prove it to me. Long story short...it's a 200A service now ;)

If this job is in Trenton, you'll meet the Inspector soon enough - he IS a nice guy, but he knows his stuff and takes no shortcuts/crap.
 
Status
Not open for further replies.
Top