Outdoor electrical help

Discussion in 'After Hours Lounge (Off Topic)' started by Kevin_Spradley, Jun 1, 2004.

  1. Kevin_Spradley

    Kevin_Spradley Stunt Coordinator

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    I need help. I have 4 incandescent bulbs around my patio in which the power comes through a 15A breaker outside near the pool equipment. The only items on the circuit are the 4 bulbs and 2 receptacles. I installed an outdoor switch but on occasion when the switch is turned on, the circuit breaker will trip. If I reset the breaker, and then try again, the lights will come on 80% of the time. Before I installed the swtich, I just used the breaker as my switch (note: the power coming to this breaker comes from a breaker in the main box in the house). I never had the problem of the breaker tripping when I was using the breaker as the switch. I was thinking short, but I have isolated all the wires from each other inside the junction box. The only thing I can think of now is in-rush current of the light bulbs. Does the breaker trip only when I am lucky enough to throw the switch when the 60Hz sine wave is at a peak?

    Any thoughts?

    Another thought, inside the house I have 8 bulbs on one circuit (4 ea on ceiling fan), but that circuit does not trip, but I do not know the rating of that breaker either. I also believe those bulbs are 60W.
     
  2. CalvinCarr

    CalvinCarr Supporting Actor

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    You installed a switch to turn on the lights that you were using a breaker to switch them off/on before? A 15 amp breaker should never trip them with out some kind of issue. Are they on a GFCI?
     
  3. TylerN

    TylerN Stunt Coordinator

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    Sounds like a bad breaker. Breakers aren't designed to be used on a regular basis as a switch, so it may be worn out. Try replacing it with a new one.
     
  4. Kevin_Spradley

    Kevin_Spradley Stunt Coordinator

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    Thanks for replies, here is some information.

    I only used the breaker at most 15 times as a switch before I installed the switch. Being outdoor, I am assuming the breaker is a GFI breaker, therefore, not a thermal overload breaker. If I understand correctly, a GFI is an instantaneous current breaker. The rating on the outside breaker is 20 amp and the one in the main panel is 20 amp, but I believe it is a thermal breaker, like the rest of the ones indoor. I am thinking about changing the breaker to a 15 amp breaker because I am installing a pond pump on that same circuit but I want to put it on a separate breaker outside.

    Testing results from last night: The breaker tripped twice out of ten tries of flipping the switch.
    With the switch in the closed (on) position and using the breaker as the switch, the breaker never tripped.

    Question repeat: Is is possible that the in-rush of 4 100W bulbs on a instantaneous current breaker is causing the tripping?

    I measured the cold resistance (~10 Ohms) of a 100W light bulb and it is very possible that a 100W light bulb can draw ~10A at cold startup.
     
  5. Justin Lane

    Justin Lane Cinematographer

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    Using the breaker as a switch is a bad thing as it will quickly wear out. Breakers are usually subject to Hysteresis losses of some kind, so each use of the breaker will result in the rated current capacity decreasing. That being said, it definitely sounds like you have a bad breaker.

    Also, remember that AC power is a time varying signal, meaning current drawn and voltage is a function of time, not a mainly constant value as in DC circuits. OHM's law in this case only gives you a current draw based on the RMS value of your AC voltage (110-120 Vac).

    J
     
  6. Kevin_Spradley

    Kevin_Spradley Stunt Coordinator

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    I understand that the AC signal is time varying. My guess right now is that when I flip the switch and the sine wave is at a peak, the breaker flips. If it is elsewhere, then it doesn't flip. As with thermal breakers, the current of the light bulb has time to settle down before the breaker will flip because of the several cycle time lag before the breaker flips. But with mag trip, they measure instanteous current, (maybe leakage current in neutral wire). At the instant a light bulb is turned out at the peak of the sine weak, the resistance is real low in the tungsten, therefore the current is high. But as the temp rises, so does resistance lowering the overall current.

    I am beginning to believe that there is no problem, just the GFI breaker working properly.

    please verify above statements.
     
  7. Kevin_Spradley

    Kevin_Spradley Stunt Coordinator

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    After thinking about common wiring practices, I am assuming that the 4 light bulbs are wired in parallel. Therefore, the instantaneous current could be 4*10Amps (40) at the peak of the sine wave.

    My electrical knowledge is limited, so any additional help is greatly appreciated.
     
  8. Bob-N

    Bob-N Supporting Actor

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    Yes, they should be in parallel. If your 10A inrush is correct (I don't know for sure), then you need to take into consideration how long the duration is. With thermal CB's, they tend to be a bit of a time delay breaking curve to allow for that inrush to pass before tripping. If your CB is tripping immediately (although intermittently), I would have to concur with the others that you have a bad or what I call "soft" CB. Give a replacement a try. CB's aren't that expensive.

    BTW, my understanding of GFI type breakers is that it is supposed to detect/open if there is excessive current flow in the ground (third prong) conductor.

    So if your CB that you mention above is a GFI style, then you might have an intermittent fault from your line/neutral conductor to ground. Check your wiring of the switch (or along the conduit path) and see if anything contacts the outlet box or conduit which should be grounded. Maybe a loose wire nut, decomposing outer insulation on wiring or stray loose wire might be the culprit.
     
  9. CalvinCarr

    CalvinCarr Supporting Actor

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    I have a GFCI tester made by greenlee. Pick one up and see if the protection is working correctly. You may be able to borrow one from an electrician or maintainance person.
     
  10. Jeff Ulmer

    Jeff Ulmer Producer

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    A GFI circuit breaker will be easily identifiable as it is much larger than a regular breaker, both length and width - and about ten times as expensive. A 20A GFI breaker is over $200CAN here.

    4 light bulbs should not trip a breaker, and that circuit is under utilised unless you have some heavy duty draws on the plugs. I assume the switch is wired correctly (breaking the hot leg), and that your grounds and common are only tied at the breaker panel. I would concur with the others that the breaker is probably shot.
     
  11. CalvinCarr

    CalvinCarr Supporting Actor

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    Holy crap...$200.00???? We get them here 20A for about $45.00 depending on the make. Thing that sucks is once you buy it there is no returning them.

    Unless there is something else you have going on it can only be the breaker.

    If memory serves me correctly the formula for finding cuurent draw=I is I=P/E or I=E/R or I= Sq. Root of P/R.

    Based on this your current draw is 3.3 amps?

    Or is it current in amps = power in watts/ voltage x cos.
     
  12. CalvinCarr

    CalvinCarr Supporting Actor

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    I checked with one of the Electrical Engineers here. I was correct. The current draw is about 1 amp per 100 watts so 4 amps is the most you should pull.
     
  13. Kevin_Spradley

    Kevin_Spradley Stunt Coordinator

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    Well I have eliminated the possibility of in-rush current causing the breaker to trip. I removed all the bulbs but one and the breaker still tripped 20% of the time. So now I believe I either have a Ground Fault or a bad breaker or both.
     

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