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Technical Data TD00405018E
Effective August 2009
Generator Sizing Guide
EATON CORPORATION www.eaton.com
System Capacity – Load Calculator
Directions for Nec 2008, Article 220, Part Iv
220.80 Optional Feeder and Service Load Calculations (RESIDENTIAL) NEC Reference
Section Can Be Used For Dwelling Units 220.82 (A)
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Served by a single feeder conductor (generator)
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120/240 volt or 208Y/120 volt service
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Ampacity of 100 amps or greater
The calcultated load will be the result of adding
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220.82 (B) General Loads, and
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220.82 (C) Heating and Air-Conditioning Load
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Calculated neutral load determined by 220.61. (Additional 70% demand factor can be
taken for cooking appliances and dryers when tables 220.54 and/or 220.55 are used)
220.82 (B)
220.82 (C)
General Loads 220.82 (B)
General Lighting and General-Use Receptacles
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Calculate at 3 VA per square foot
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Use exterior dimensions of the home to calculate square footage – do not include open porches, garages,
or unused or unfinished spaces not adaptable for future use.
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Add 20-amp small appliance & laundry circuits @ 1500 VA each
Calculate the following loads at 100% of nameplate rating
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Appliances fastened in place, permanently connected or located on a specific circuit
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Ranges, wall-mounted ovens, counter-mounted cooking units (Tables 220.54 & 220.55)
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Clothes dryers not connected to the laundry branch circuit
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Water heaters
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Permanently connected motors not included in Heat & Air-Conditioning Load section
220.82 (B) (1)
220.82 (B) (2)
220.82 (B) (3)
220.82 (B) (3) a
220.82 (B) (3) b
220.82 (B) (3) c
220.82 (B) (3) d
220.82 (B) (4)
Heating & Air-Conditioning Loads 220.82 (C)
Include the largest of the following six selections (kVA load) in calculation
Air Conditioning and Cooling
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100% of nameplate rating
Heat Pumps Without Supplemental Electric Heating
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100% of nameplate rating
Heat Pumps With Supplemental Electric Heating
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100% of nameplate rating of the heat pump compressor*
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65% of nameplate rating of supplemental electric heating equipment
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If compressor & supplemental heat cannot run at the same time
do not include the compressor
Electric Space Heating
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Less than 4 separately controlled units @ 65% of nameplate rating
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4 or more separately controlled units @ 40% of nameplate rating
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40% of nameplate rating if 4 or more separately controlled units
Electric Thermal Storage (or system where the load is expected to be continuous at nameplate rating
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100% of nameplate rating
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Systems of this type cannot be calculated under any other section of 220.82 (C).
220.82 (C) (1)
220.82 (C) (2)
220.82 (C) (3)
220.82 (C) (4)
220.82 (C) (5)
220.82 (C) (6)
Load Calculations
General Lighting Load
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Small Appliance & Laundry Circuits
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General Appliances & Motors (100% rated load)
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Sum of all General Loads = Total General Load (VA)
Apply Demand Factors
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First 10 kVA @ 100%
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Remainder of General Loads @ 40%
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HEAT / A-C LOAD @ 100%
3 VA x ft²
+ 1500 VA per circuit
+ Total general appliances
Total general load (VA)
= 10,000 VA
(Total VA - 10,000) x .40
= Calculated General Load (VA)
Largest Heat or A-C Load (VA)
= TOTAL CALCULATED LOAD
Converting VA TO kW (Single-phase applications with 1.0 power factor only) 1 kVA = 1 kW
(4 Seiten)
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