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What size fuse for 220Watts of light?

Discussion in 'Strobe Lighting' started by Maleko, Dec 20, 2010.

  1. Maleko

    Maleko Senior Member
    from Ct
    Messages: 778

    If i have 220 watts of backup lights what size fuse do i need?
    I have 4 55watt light i want to wire to one switch for back up and my sander as well
    Also what size relay as well?

    Thanks in advance..
     
  2. jb1390

    jb1390 Senior Member
    Messages: 710

    220 / 12 volts = 18.3 amps
     
  3. RBRONKEMA GHTFD

    RBRONKEMA GHTFD 2000 Club Member
    Messages: 2,592

    a 30 amp relay will do the trick, I would feed the relay with a 10 ga wire directly off the battery with a 20 amp fuse on that. Then wire the relay accordingly.
     
  4. jb1390

    jb1390 Senior Member
    Messages: 710

    20 amps will probably blow.....your charging circuit can put out 14 volts, which will up your current to 21.5 amps. I would probably use a 30 amp relay, 25-30 amp fuse, and 12-10 gauge wire. Also make sure your connections are cleaned, greased, and tight. Most hot spots are caused by poor contact resistance as opposed to the wire itself.
     
  5. Maleko

    Maleko Senior Member
    from Ct
    Messages: 778

    Big Thanks to all...
     
  6. RBRONKEMA GHTFD

    RBRONKEMA GHTFD 2000 Club Member
    Messages: 2,592

    Thanks for that, I forgot to take that into account.
     
  7. wkahler

    wkahler Senior Member
    Messages: 250

    Go with LEDS and you won't have to worry about the relay and the major electrical pull, LOL!!! ;)
     
  8. Maleko

    Maleko Senior Member
    from Ct
    Messages: 778

    I know.. That was my first plan..

    But i got some for free, Hella 55watters . So ill take em....
     
  9. slongfellowii

    slongfellowii Senior Member
    Messages: 157

    More voltage will pull less current/amperage or about 15 amps. Watts= amps x volts.
    Fuses rating is usually determined by the amount of current that the wire is rated to carry.
     
    Last edited: Dec 21, 2010
  10. jb1390

    jb1390 Senior Member
    Messages: 710

    Second part is true. First part is way off base. The 55 watts is calculated at a nominal voltage (12v). Lights are not constant power-they are more or less constant resistance. As your voltage increases, so will light output (and current draw), because they draw more power. In this case, the size wire and fuse are determined by the current draw.


    A 12 gauge wire will easily carry 30 amps. (DC)
     
  11. slongfellowii

    slongfellowii Senior Member
    Messages: 157

    You are right, I was thinking more in terms of a plow drawing more current when there is a voltage drop.