Please help understand NEC Article 220.84(A)(2)

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aaSpencer

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Thank you for the opportunity to post a question here. Please help me understand the NEC Article 220.84(A)(2):Each dwelling unit is equipped with electric cooking equipment.
Exception: When the calculated load for multifamily dwellings without electric cooking in Part III of this article exceeds that calculated under Part IV for the identical load plus electric cooking (based on 8 kW per unit), the lesser of the two loads shall be permitted to be used.

There is an existing building with 120/208 volts 3 phase 400 Amps that will be renovated into a (12) unit apartment. Electric water heater is 4.5 KW and combined gas PTAC is 3.8 KW for each unit.

If gas stove is installed, Table 220.84 is not applicable. and because of that, the calculated load will be around 154,600 KVA or 430 Amps.

If ‘exception’ (if allowed) is applied, 12*8000 = 96 KW is added, the total connected load now is at 250 KVA and at 0.41% demand factor, the feeder drops to 285 Amps.

And choosing the lesser of the two, clearly, the ‘exception’ will be used as permitted. So though, the electrical drawing will show as gas stove, the load calculation of 285 Amps can be applied to justify that the existing 400 Amps can be re-used.

Is that about right? Please advise on the best approach. Thank you in advance.
 
What is the square footage of each unit? Does each unit have its own laundry? Dryers gas or electric? What are the appliances that are going to be in each unit? Each unit identical? House loads? Not enough information to do a calculation! See that you have been a member for a while but it does not say what your occupation is.
 
Hi,
Thank you for the response. My occupation is electrical designer/programmer.

The building is a single story with a full basement from end to end. (12) units set up in a row.
Each unit is 540 sq ft. (30'x18'), simple setup with ref, food disposal, no dishwasher, no washer/dryer, 4.5KW water heater, 3.8KW PTAC(gas) and electric stove for each unit.
House load are (2) wall heaters for stairs to basement at both ends of building, each at 3KW each. (4) Washer/dryer(gas), basement lights @ 600watts and wallpacks @240watts. (parking lot fed from another building)

Hope this has enough info.

Thank you.
 
aaSpencer said:
Hi,
Thank you for the response. My occupation is electrical designer/programmer.

The building is a single story with a full basement from end to end. (12) units set up in a row.
Each unit is 540 sq ft. (30'x18'), simple setup with ref, food disposal, no dishwasher, no washer/dryer, 4.5KW water heater, 3.8KW PTAC(gas) and electric stove for each unit.
House load are (2) wall heaters for stairs to basement at both ends of building, each at 3KW each. (4) Washer/dryer(gas), basement lights @ 600watts and wallpacks @240watts. (parking lot fed from another building)

Hope this has enough info.

Thank you.
Click to expand...
You need to read all of 220.84. Let’ see what you come up with after doing your calculations.
 
aaSpencer said:
Hi,
Thank you for the response. My occupation is electrical designer/programmer.

The building is a single story with a full basement from end to end. (12) units set up in a row.
Each unit is 540 sq ft. (30'x18'), simple setup with ref, food disposal, no dishwasher, no washer/dryer, 4.5KW water heater, 3.8KW PTAC(gas) and electric stove for each unit.
House load are (2) wall heaters for stairs to basement at both ends of building, each at 3KW each. (4) Washer/dryer(gas), basement lights @ 600watts and wallpacks @240watts. (parking lot fed from another building)

Hope this has enough info.

Thank you.
Click to expand...
aaSpencer said:
Hi,
Thank you for the response. My occupation is electrical designer/programmer.

The building is a single story with a full basement from end to end. (12) units set up in a row.
Each unit is 540 sq ft. (30'x18'), simple setup with ref, food disposal, no dishwasher, no washer/dryer, 4.5KW water heater, 3.8KW PTAC(gas) and electric stove for each unit.
House load are (2) wall heaters for stairs to basement at both ends of building, each at 3KW each. (4) Washer/dryer(gas), basement lights @ 600watts and wallpacks @240watts. (parking lot fed from another building)

Hope this has enough info.

Thank you.
Click to expand...
What is the amperage for the disposals? How many square feet are the common hallways? Is that a total of 4 wall heaters for the stairways?
 
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