feeder demand on a duplex

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cmetwinkle

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Puyallup WA
How do you calculate feeder demand on a duplex dwelling .. Do you calculate the single dwelling then multi by 2.. DO you omit laundry load like you would in a multi dwelling . Hopefully someone could take me step by step Thanks for the help you would be my hero for the day
 
charlie b

charlie b

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I am not sure you are using the term "feeder" correctly, since I do not know how power gets to this duplex building. So let me ask several questions.

  1. Are you talking about calculating the load to the entire building, so as to size the conductors and the disconnect for the entire building?
  2. Is the power to the building coming directly from the utility (i.e., is this a "service" calculation)?
  3. Are you talking about calculating the load within one or both of the units individually, so as to size the unit's power panel and the conductors feeding each panel?
The basic concept is that you perform a calculation to size one panel (and the conductors serving that panel) at a time. To size a unit's panel and its feeders, calculate only the loads within that unit. To size the service to the two-unit building, add the loads from both units, and take advantage of any demand factors that apply in consideration of the equipment in both units.

For example, suppose each of the two units has a disposal and a dishwasher. That is only two fastened in place appliances. So when you calculate the load on either single unit, you don't get to use the 75% demand factor of 220.53. However, when you calculate the service to the duplex building, you have a total of four fastened in place appliances. Therefore, you can use the 75% demand factor of 220.53.
 
charlie b

charlie b

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cmetwinkle said:
Do you omit laundry load like you would in a multi dwelling?
Click to expand...
Where did you get the notion that you omit laundry load on a multi-family dwelling unit? Every dwelling unit calculation has to include 1500 VA for a laundry circuit, unless it is a multi-family building for which either (1) A common laundry area is provided, or (2) Laundry facilities are expressly forbidden by the owner. Many multi-family dwelling units do not meet either of these two criteria, and do indeed have laundry facilities in each unit.

The reference trail is a bit tricky, but start at 220.52(B), which directs you to 210.11(C)(2), which in turn directs you to 210.52(F).
 
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cmetwinkle

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Location
Puyallup WA
duplex dwelling

duplex dwelling

feeder demand you have a duplex each dwelling in that duplex has:

it is 1600 sq ft
5 Amp 120 V Garbage Desposal
11 Amp dishwasher
4.5 kw Hotwater heater


20,000 va heater
two 23 Amp 240 airconditioner
and a 11 kva Range


both units are fed by one 120 /240 v What is the feeder demand
 
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