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    omarromy's Avatar
    omarromy Posts: 1, Reputation: 1
    New Member
     
    #1

    May 21, 2011, 04:40 AM
    What is the formula to get the size of wire and size of breaker for 400watts lamp
    Electrical load
    cdad's Avatar
    cdad Posts: 12,700, Reputation: 1438
    Internet Research Expert
     
    #2

    May 21, 2011, 05:58 AM

    Watts / voltage = amps
    sinnadurai's Avatar
    sinnadurai Posts: 127, Reputation: 2
    Junior Member
     
    #3

    May 22, 2011, 04:30 PM
    For lamps incorporating ballasts like fluorescent lamps multiply by 1.6
    ballengerb1's Avatar
    ballengerb1 Posts: 27,378, Reputation: 2280
    Home Repair & Remodeling Expert
     
    #4

    May 22, 2011, 04:46 PM

    Can you claarify that, multiply what by 1.6? Omarromy can you tell use what you are doing and where you live. If this is a single fixture in a residence we use 14/2 wire with a 15 amp breaker pretty much standard.
    sinnadurai's Avatar
    sinnadurai Posts: 127, Reputation: 2
    Junior Member
     
    #5

    May 22, 2011, 05:22 PM
    Comment on ballengerb1's post
    In BS7671 it is mentioned to multiply the current by 1.6 to select the wire size.Breaker size depends on quantity of lamps connected or load. Normally in homes and offices 6A mcb is used. In factories where many fittings are connected to a single switch the engineer should calculate or consultant should specify in drawings
    ballengerb1's Avatar
    ballengerb1 Posts: 27,378, Reputation: 2280
    Home Repair & Remodeling Expert
     
    #6

    May 22, 2011, 06:37 PM

    Not sure what "BS7671" is but, in the USA, lets look at a typical residential circuit. 14 gauge wire is rated to carry 15 amps at 120 vac. There is no number in this sequence of 14, 15 and 120 that you can multiply by 1.6 and get 14 gauge wire.
    sinnadurai's Avatar
    sinnadurai Posts: 127, Reputation: 2
    Junior Member
     
    #7

    May 23, 2011, 03:05 AM
    in BS practicing countries,lighting circuits are fed at 240V 50Hz and it is the normal practice to use 1mm^2 pvc insulated cables or sometimes 1.5mm^2 depending on the load
    sinnadurai's Avatar
    sinnadurai Posts: 127, Reputation: 2
    Junior Member
     
    #8

    Jun 5, 2011, 05:34 AM
    Comment on ballengerb1's post
    The load in a lamp circuit incorporating a ballast(fluorescent) is the lamp watts plus the loss in the ballast. That's why a multiplying factor of 1.6 is recommended by the Institution of electrical engineers,UK.

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