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electric & safety

What is an AFCI and why should I install one?

Why use a AFCI?
“An afci is not needed per say, but if there is any exposed wiring in high traffic areas… for example a T-104 set up on the wall next to a door, STJ cords running along the ground, cable inside a cab to some duplexes that kind of thing, then I would install one. They are only like $35 and I\'ve seen them (rated) up to 40A.”



AFCI stands for Arc Fault Circuit Interrupter.

AFCI's are a very neat safety device that have the ability to prevent:

  • Low level arcing cause buy high moister, dust or impaired wire insulation.
  • Shorts from ground (Exp: exposed hot contacting a grounded box)
  • Shorts (Exp: sudden large power surge from hot contacting neutral)
  • Normal curcuit breaker, shuts off the power to a circuit overheated wires from an over load.

    Note: circuit breakers are thermally activated. They trip if power going thru them exceeds their rating. The breaker contacts heat up and trips. This can take time, depending on the load.

    Note: ground shorts and shorts can occur with both GFCI and AFCI, but the damage will be minimal.

    Used in conjunction with a GFC receptacle, gives you some of the best protection there is.

    All AFI’s come with instructions and clear wiring diagram (some are different). They should only be installed by a licensed electrician.

    If you can install a breaker and run a circuit here is a stealth tip:

    If you live in a home, or have had a bed room circuit upgraded since 2002 (USA), there is most likely an AFCI in your breaker box for each bed room (To avoid some one asking why you have 3 afi’s in a two bed room house)

    You can use a regular breaker in the main panel, then run a small sub panel for the afi, (see pic below). That is an option you can take. This can also function as a main cut off for a small to med sized grow.
  • Arc fault breakers have GFCI protection built in.

    2005 code for new residential construction specifies AFI protection required for bedrooms only. GFCI protection for kitchen, bath, laundry, garage, patio/hot tub/outdoor circuits.

    Arc Fault Breakers work poorly on HID arc lamps for obvious reasons.

    GFCI circuits also exhibit nuisance tripping with some fluorescent/HID loads.

    No guidelines for number of circuits per bedroom, although good practice dictates that a bedroom should be served by 2 circuits. This can be done in two bedrooms with 2 circuits total.