demand loads/demand factors

[crudeoil]

Hello!

Could someone please help me figure out the answers to these three questions? Could you also tell me the formula for figuring it out please? Thank you very much.


#1) 2,000 sq.ft. house... What is the demand load for all loads to which lighting feeder demand factors apply? Watts?

#2) Two 5.5 kW dryers in a duplex adds how many amps to the demand load of the 120/240-volt service?

#3) 1,200 sq.ft. apartment, the lighting and small appliance circuits are on 20-amp, 120-volt circuits. Laundry facilities are available to the tenants in the complex. How many 20-amp circuits are required in the apartment?

[ March 03, 2005, 04:37 PM: Message edited by: crudeoil ]

 

[bphgravity]

Re: demand loads/demand factors

All three of these questions are answered by following the requirements of Article 220. (2002 NEC)

1. Start at 220.3(A) to figure the general lighting load. See 220.3(B)(10) to see what that load includes. Next, go to 220.16(A) and (B). These loads are permitted to be included in the general lighting demand. Finally, see 220.11 to determine the demand that needs to be applied to the feeder or service of the general load you have calculated.

2. See 220.18. Determine if a demand is permitted. Once you find the total kW (va), use Ohm's Law to determine load in amperes.

3. Start the same as question one by determining the general lighting load. Remember to include 220.16, except this time, you need to review 210.52(F) and its exception for laudry considerations. Don't apply a demand factor, use the entire general load. Take the entire ligthing load in va, divide by the connected voltage, divide that by the branch circuit rating, that is your answer. You must round up for any remainder.

Go ahead and post your calculations and we can go over them.