Dwelling service calculations

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  1. The code lists what 3 things that you shall have in a dwelling? PP. 183, Calculations, Tom Henry, 2011.
    • The code lists 3 things you shall have in a dwelling.  
    • 1.) 3VA per square foot of living area 
    • 2.) 2 x 1500 VA small appliance branch circuits
    • 3.) 1 laundry circuit at 1500 va: UNLESS it is ELECTRIC, then it must be 5KVA min.
  2. What is the outline and acronym used as a checklist for calculating residential loads? PP.165 NJATC, Code Calculations, 2011
    • loc’d stall heating
    • Lighting and general receptacle load 
    • square footage x 3 VA then, VA/E = I/15a= number of circuits (round up)
    • Other Fastened in place appliance loads
    • Cooking appliance load
    • Dryer load: 5kva minimum electric or 1500 for two wire (120v)
    • Small appliance load: 2 x 1500v a laundry and bathroom. 
    • Twenty five percent of largest motor load
    • Air Conditioning load or heating
    • Laundry load (1500VA gas or 5KVA min.)
    • Heating load or AC 
    • ……..are not counted as the four fastened in place appliance which may be derated to 75%.  Water heater, dishwasher, disposer, trash compactor, ventilation hood and sump pump are.
  3. Is the lighting load for a dwelling used in table 220.42 for determining the minimum number of branch circuits in a dwelling? What is the minimum number of branch circuits in a dwelling? Hint: T220.42 is lighting demand factors.
    • NO.
    • General lighting = 1
    • small appliance = 2
    • laundry            = 1
    • Bathroom         =1

                          5 minimum total
  4. the minimum size service to a house is what? NEC 2011: 230.79C
    100 amps
  5. What are you allowed to omit in a dwelling service calc? NEC: 220.60
    The smaller of two loads, of either heat or air conditioning. Considered non-coincidental loads, or loads you are likely to not use at the same time.
  6. section 220.53 states that it shall be permissible to apply a demand factor of 75% to the nameplate-rating load of how many fixed appliances and of what type?
    4 or more and of the following: dishwasher, water heater, disposal, compactor, ventilation hood, sump pump, are examples.
  7. Heat and AC are calculated at what percent?
  8. What is the minimum VA for an electric clothes dryer?
    5KVA per section 220.54
  9. the maximum unbalanced load (neutral) for a feeder supplying household electric ranges, wall mounted ovens counter mounted cooking units, and electric dryers, shall be what %? per 220.61B1
  10. What happens with more than 4 household electric clothes dryers?
    They must be derated at a demand factor percentage per T220.54
  11. the 70 percent demand factor for unbalanced load changes once 200 amps is exceeded, how?
    220.61B2 states that the first 200 amps is at 100 percent followed by the rest at 70 percent.
  12. What must you remember regarding voltage and an unbalanced load regarding 120v calcs? PP 193 Tom Henry
    that the 120 volt circuit will never be included in a neutral calculation.
  13. The General load is considered what in a dwelling calculation?  Used when?
    • lighting - 3va per sq ft
    • 2 small appliances - 3000va (1500 va ea)
    • 1 laundry - 1500 va


    In optional or general method.
Card Set:
Dwelling service calculations
2017-05-12 16:29:50
dwelling service calculations

From 2011 Tom Henry’s Code calcs and NJATC text
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