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Technical Electrical: circuit breaker works in place of inline fuse?

Discussion in 'Traditional Hot Rods' started by Humboldt Cat, Sep 29, 2013.

  1. Humboldt Cat
    Joined: Feb 20, 2003
    Posts: 2,235

    Humboldt Cat
    Member
    from Eureka, CA

    Am in the middle of rewiring the path from my electric fuel pump, isolating it away from the main fuse box, calls for a 30A inline fuse between the relay and battery. Found a new 30A circuit breaker forgot I'd had, could save me a trip to the store.
    Will this inline breaker work in it's place?
     
  2. killbilly
    Joined: Mar 29, 2009
    Posts: 283

    killbilly
    Member

    Yes it will work just fine,it does what it is,it will reset after cooling off,if it kicks off again you have a short
     
  3. In theory it seems like it should work OK. But for automotive use it seems like circuit breakers are mainly used in higher amp draw circuits with short term usage. Things like power windows and power seat adjusters. Unfortunately I don't know why this is, and it may just be a coincidence.

    Provided that the breaker is working properly I don't see any harm in trying it. Maybe the breakers are more or less sensitive to current spikes. Don't know if fuel pumps are prone to those issues, maybe a current spike when first turned on that trips a breaker?

    At work I see customers wanting to replace circuit breakers assuming that they are the reason their power windows quit working. I'm sure that the breaker can fail, but I doubt that they ever consider that there's maybe something wrong in the circuit that's creating a high amp load which is causing the breaker to do its job.
     
  4. 1971BB427
    Joined: Mar 6, 2010
    Posts: 8,892

    1971BB427
    Member
    from Oregon

    Only drawback to breakers is in a high resistance short. They will continue to reset and trip, so each time you have the chance of igniting the insulation unless the wire melts in half. I'm not a breaker fan. I'd rather have a fuse blow and keep the circuit open until I can find the short.
     
  5. 19Fordy
    Joined: May 17, 2003
    Posts: 8,114

    19Fordy
    Member

    1971BB427 sounds the most sensible and safe. Use an in line fuse.
    Isn't 30 AMPS kind of high. I use a 15 amp for my electric fuel pump.
    What's the data on the pump say?
     
  6. gasserjohn
    Joined: Nov 9, 2008
    Posts: 1,218

    gasserjohn
    Member

    each time it heats up & trips it is weaker trips easier
     
  7. Why not just go hey an inline atc fuse holder and fuse.
     
  8. 1971BB427
    Joined: Mar 6, 2010
    Posts: 8,892

    1971BB427
    Member
    from Oregon

    Most hi performance electric fuel pumps draw about 3 amps contiuous, and even with inrush currents they wont go over maybe 7 amps. I always use a relay, and a 20 amp fused circuit across the contacts to feed the pump, with #12 wire. (rated 20-25a depending on insulation)
     
  9. Humboldt Cat
    Joined: Feb 20, 2003
    Posts: 2,235

    Humboldt Cat
    Member
    from Eureka, CA

    ?Que?
     
  10. Humboldt Cat
    Joined: Feb 20, 2003
    Posts: 2,235

    Humboldt Cat
    Member
    from Eureka, CA

    Thanks for the feedback. Got it all hooked up, Fuel Pump grounded to frame and connected to Relay, Relay branches out to battery (with CB, replace with fatty fuse tomorrow) as well as floor-mounted toggle, grounded to frame.
    Nothin yet, trying to recall where/what prong two of the toggle should go to... ground, I think....
     
  11. Humboldt Cat
    Joined: Feb 20, 2003
    Posts: 2,235

    Humboldt Cat
    Member
    from Eureka, CA

    Fuel Pump power line used to go to fuse box (fuse-tapped), but disconnected that from the box, connected it to relay...
     
  12. Humboldt Cat
    Joined: Feb 20, 2003
    Posts: 2,235

    Humboldt Cat
    Member
    from Eureka, CA

    I'll get an inline fuse this week, just broke-Sunday and wanted to get the main setup up, for today...
     
  13. greybeard360
    Joined: Feb 28, 2008
    Posts: 2,089

    greybeard360
    Member

    There are a lot of cars that also have CB in the wiper circuit. Nothing wrong with using a breaker in the FP circuit, it might just get you safely off the side of the road some time not having to stand along the freeway to replace a blown fuse. (I feel this is the reason behind CB in wiper and HL circuits). The reasoning behind CB in power seat and window circuit is there is no "stop" built in and if someone sits there holding the button too long the motor could burn out.
     
  14. 1971BB427
    Joined: Mar 6, 2010
    Posts: 8,892

    1971BB427
    Member
    from Oregon

    Fuel pump switch should be fed from a smaller 1-2a fused control circuit. Then to a switch and out of the switch to the coil of the relay. The other side of the relay's coil should be grounded. The power fuse (suggested 20a.) should go to one side of the contacts, and the other side to your fuel pump. The other side of the pump lead to ground.

    [​IMG]
     
  15. Humboldt Cat
    Joined: Feb 20, 2003
    Posts: 2,235

    Humboldt Cat
    Member
    from Eureka, CA

    That's how I have it set up, except I'm missing a connection to one of the toggle's two prongs. Trying to avoid fuse-tapping it back into the fuse box (unless the short from before would now be prevented by the inline relay system).
     
  16. nunattax
    Joined: Jan 10, 2011
    Posts: 3,102

    nunattax
    Member
    from IRELAND

    i first came accross relays rewireing my 77 xlch.i didnt trust them at first.but when the headlight circuit tripped out one evening in the middle of nowhere i soon spotted the problem and was able to make it home with lights.i didnt have a pocket full of fuses.once the relay reset i was good to go.a great invention

    at a later date i had a circuit breaker fail but that was on a 75 flh stroker thatwas over 35 years old at the time
     
  17. Humboldt Cat
    Joined: Feb 20, 2003
    Posts: 2,235

    Humboldt Cat
    Member
    from Eureka, CA

    Headlight relay is actually next on my list....
     
  18. nunattax
    Joined: Jan 10, 2011
    Posts: 3,102

    nunattax
    Member
    from IRELAND

    over here available from your local harley dealer at inflated pricrs
     
  19. Humboldt Cat
    Joined: Feb 20, 2003
    Posts: 2,235

    Humboldt Cat
    Member
    from Eureka, CA

  20. nunattax
    Joined: Jan 10, 2011
    Posts: 3,102

    nunattax
    Member
    from IRELAND

    to the thread
     
  21. Oh hell, Tim, just do it the Eureka/Arcata "Tweeker " way, and wire that sucker direct...figure 14 gauge wire will melt at about 35 amps anyway, so there ya go... 8=)
    (just kidding, HAMB-ers, just kidding)
    I guess I missed the antique drags at Samoa, huh? and don't forget, Sea Cruise is coming up fast, been out in the garage during this rain storm with the radio on, workin' on the '26 and the '57...
     
  22. Humboldt Cat
    Joined: Feb 20, 2003
    Posts: 2,235

    Humboldt Cat
    Member
    from Eureka, CA

    DAVE! yes, you did. When is the Sea Cruise? Rain here, too, trying to wrap up this under-the-truck stuff soon... my duplex garage leaks ground water from the retaining wall, like the Blob, slowwly advancing its stream towards my work area, gotta get back to it...
     
  23. I think your response answers my question but that diagram seems to be lacking something. Somewhere in that "red wire" circuit there should be another fuse for the fuel pump, correct? Would it make any difference which side of the relay the fuse was installed on?
     
  24. REBEL43
    Joined: Feb 17, 2007
    Posts: 722

    REBEL43
    ALLIANCE MEMBER
    from TENNESSEE

    The wire on the 86 terminal in drawing has a draw of 150 to 200 milliamps, triggers the relay only.
     

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