Table 220.84 NEC2002

Status
Not open for further replies.
J

joberrios

Member
I have a project that consists of 3 residential buildings, each with 30 apartments. All 3 buildings are powered by the same substation (1500 KVA). The utility point of connection is at a switchgear (13.2 KV). I run a service conductor from the switchgear to the substation. From the substation I run an individual feeder to each building. In order to obtain the substation size or the service conductor size, using the optional calculation method, can I use the total number of apartments (90) for my demand factor or do I have to take each individual feeder load per building (demand factor for 30 apartments) and add that load to obtain my total load? If I use 90 apartments the demand factor is 0.23 based on Table 220.84. If I use 30 apartments the demand factor is 0.33. Please let me know your opinion about this subject
 
When sizing any wire, you use the number of units that are powered through that wire. For the service, you use 90 units. For the feeder to each building, you use 30 units.
 
Table 220.32

Table 220.32

The thing is that the code define a multyfamily dwelling unit as a building but not buildings!!

Read carefully article 220.32 when it said "supplies more than two dwelling units of a multyfamily dwelling"...:)
 
Section 220.84 mentions you can use Table 220.84 for "a multifamily dwelling." My interpretation of this is that by using the letter "a" in front of multifamily, the code is refering to a single building. Therefore the NEC allows you to use this table for each individual building and not for a combination or several buildings. You would have calculate the load per building an add them up to size your substation.

Feel free to comment or clarify my understanding of this issue.

Sincerely,

Gustavo Rieckehoff, P.E.
 
Status
Not open for further replies.
Top