KMAC Engineering
N.Y.S. Licensed Professional Engineer
(K. Alfred Chu, PE)

Electrical Design:

• Sizing conductors/ circuit breakers

  Sizing electric service

  Sizing grounding electrode conductor size

  General cable types

  1. Romex (nonmetallic sheathed cable)

  • not in buildings >3 floors
  • min. 1/4in sheathing into box
  • protect from physical damage
  • nail plate req'd when cable is 1 1/4in of stud edge
  • Clamped to box with approved NM clamp
  • max. bend radius(5 x diameter)
  • staple within 12in. of box and every 4 1/2 ft

  BX (armor-clad cable)

  • stapled min. every 4 1/2 ft. & within 12in. of box
  • insulated bushing at terminations
  • nail plate req'd where cable is 1 1/4 in. of stud face

  General Purpose Circuits

  1. Receptacles

  • any wall>2ft. wide req's receptacle
  • 6 ft. cord can be plugged in anywhere along wall
  • hallway>10ft. req's receptacle

  Lights

  • switched lighting outlets req'd in all habitable rooms,baths,halls,stairs (3 way/>6 steps),garages,outdoor entrances,storage or utility area,attics,basements
  • recessed light 3in. from insulation

  Paddle Fans

  • not to be supported by standard electrical boxes

  Bathroom

  • GFCI req'd adjacent to basin
  • Bathroom receptacles req. separate 20A circuit

  Kitchen Circuits

  • Two 20A small-appliance circuits req'd
  • countertop-min. 2 small-appliance circuits
  • no lighting permitted on these circuits
  • counters>12in wide red. receptacles
  • GFCI protection for all countertop receptacles
  • GFCI-protect any receptacle within 6ft. of sink

  Appliances

  • electric range-min. 40A wire (#8 copper)
  • garbage disposal cord must be > 18in. but <36 in.
  • garbage disposal/dishwasher on single duplex receptacle(3-wire 240V) req's a tie-bar breaker
  • dishwasher cord(under sink) 3-4ft. long
  • plugs of fixed appliance accessible

  Utility

  1. Laundry

  • separate 20A circuit req'd for laundry
  • electric dryer min. feed 30A #10 THHN wire

  Gas Furnace

  • fused (125%) disconnect (SSU switch)
  • lighting outlet switched at entry req'd
  • separate circuit
  • 120V receptacle on the same level and within 25 ft.

  Water Heater

  • in-sight disconnect
  • bond hot,cold and gas pipes

  Heating Units

  • branch circuit-125%
  • maximum 48A unsubdivided load

  Air Conditioning

  • window-unit cord and plug OK if controls are <6 ft. of the floor
  • 120V window-unit cord max. 10 ft.

  Conduit Systems

  1. General Requirements

  • openings to conduit system must remain accessible
  • no common plastic boxes with metal raceway, BX or MC cable
  • crimps(kinks) in pipe not permitted

  EMT (electrical metallic tubing)

  • not approved for burial unless coated
  • rain-tight fittings outside
  • supported within 36 in. of any box and every 10ft.

  Flexible Metal Conduit

  • dry locations only
  • support min. every 4 1/2ft. & within 12in. of box
  • angle connections may not be concealed

  Liquid-tight

  • same as flex

  Boxes

  • metal boxes grounded with approved method
  • wallboard repaired-no gaps> 1/8 in. to outlet box
  • boxes and conduits must remain accessible
  • outlet boxes shall be flush with combustible surfaces
  • min 6" of free conductor in box

  Garage

  • min one lighting outlet & one GFCI receptacle req'd
  • all receptacles GFCI-protected except single receptacle,inaccessible behind a fixed appliance
  • subpanels shall not penetrate modified 1hr. wall
  • detached garage req'd grounding electrode

  Outdoors

  • receptacles at grade front & rear GFCI-protected
  • doors to outside req. lighting outlet
  • rain-tight cover for unattended cords
  • boathouse receptacles must be GFCI-protected

  Closet

  • enclosed incandescent-12in. of clearance
  • surface fluorescent or recessed incandescent- 6in.
  • no open incandescent bulb-type fixtures
  • no new breaker panels