Hot fuse box

Discussion in 'Electrical Forum discussion & Blog' started by bqz, Dec 3, 2007.

  1. bqz

    bqz New Member

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    Have problem with fuse box getting very hot.

    Here is what I'm working with.
    Just bought a new dryer hooked wires up correctly to dryer three prong.
    dryer runs to old pushmatic breaker (twin 30 I believe) well the dryer keeps kicking off one side of the breaker on occasion ,the dryer keeps running with no heat.Also the box with push breaker hums a little sort of like a florescent bulb just starting, in conjunction with all this the main in the fuse box is getting very very hot ,so hot you can't touch it and you can smell an electrical burn sort of.
    Yes it is a"fuse box" with screw in fuses.
    So what's the deal why is it getting so hot ? it didn't do it on the old dryer but now it is ,anyone have any ideas??It only gets hot when the dryer is running.
    Please note I have an electric stove as well not on same circuit but same box I wonder if running both at same time is problem??

    so you know I'm not going to run it until I fix it. Duh!
  2. Alectrician

    Alectrician DIY Senior Member

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    689
    Call someone.
  3. bqz

    bqz New Member

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    Already have have !!
    Was wondering if anyone knew what was causing it so when the electrician comes I might know if he's telling me the right thing.Don't want some fellow coming in and blowing me a bunch of smoke and try to sale me things I don't need.
    So the question is does anyone have an idea as to why this would do what it's doing???
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Heat means current so the simple answer is something for some reason is drawing to much current.

    By the way who installed the dryer?
  5. bqz

    bqz New Member

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    14
    That would have been me,hooked up like the book showed.
    You think problem might be there?? I checked it twice to make sure.
  6. Alectrician

    Alectrician DIY Senior Member

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    689
    There are several places wher it could have gone south starting with YOUR installation.

    The pigtail is hard to screw up.....but I think you could do it :)

    The center terminal is generally the ground with the two to the left and right are hot.

    The flat style gray pigtail has the ground in the middle and hots on the outside just like the terminal configuration.

    The round style black cords will have a red and black for the hots aith a white for the ground.


    The electrician will check the wiring/terminal connections at the dryer, the outlet and the panel. If everythin appears OK it could be a defective dryer.


    I suspect your work though. Check it again. Take a pic.
  7. Bob NH

    Bob NH In the Trades

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    Excessive heat is often caused by high current through a high resistance contact. The current may be within limits.

    The contact may be a wire junction or it may be a bad breaker or fuse. You can usually detect it by checking the voltage drop across suspected connections.
  8. bqz

    bqz New Member

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    14
    Thanks for the input fellows I have an electrician stopping by tonight to check it out ,I'll repost tomorrow and let you know what I've found out.
    Thanks again
  9. jwelectric

    jwelectric Electrical Contractor/Instructor

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    ???????????????? :confused::confused::confused:

    One or the other of us are confused. How can you have a "high current" through "high resistance"?
  10. Alectrician

    Alectrician DIY Senior Member

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    689
    This was my thinking too in a past post but I just got ridiculed about ohm's law instead of educated.

    If the resistance goes up wouldn't the amperage go up? If not, why do burned connections often cause so much heat that the insulation burns off the wires. Wouldn't it take high amps to burn insulation?


    I am just going by what I have seen.

    Bad connection causes lots of carbon like black crap = more resistance, conductivity gets progressivly worse, wire gets hot and isulation melts?

    I am probably looking at it wrong.
  11. Wet_Boots

    Wet_Boots Sprinkler Guy

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    "Hot fuse box" puts me in mind of a practical course in electronics I took, and lesson one (Ohm's Law) touched on fuse box fires. About a year later, in an old rented house, I heard a sort of sputtering/hissing kind of noise in the basement, and it came from a fused control box for an electric water heater. Just like in the lesson, a bad contact was becoming resistive, and building up heat. Got my money's worth on that course.
  12. Bob NH

    Bob NH In the Trades

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    jwelectric; I was replying to your statement: "Heat means current so the simple answer is something for some reason is drawing to much current."

    My complete statement was: "Excessive heat is often caused by high current through a high resistance contact. The current may be within limits."

    If you have a 5500 watt dryer that is drawing 5500 Watts /240 Volts = 23 Amps and about 10.5 Ohms of resistance, and you add about 0.5 Ohm with a bad contact or connection somewhere in the circuit, you will still have about 22 Amps. Therefore, the current is not excessive; it is within the expected limits of the circuit.

    However, there is a lot of heating in the connection that has the high resistance. Since power = Amps squared x Ohms; there would in that case be 22x22x0.5 = 242 Watts being dissipated in that junction. That is a lot of heat in a bad connection.

    That 242 Watts is what I was referring to when I said: "Excessive heat is often caused by high current through a high resistance contact. The current may be within limits."

    There IS excessive heat in the junction, AND the current is within limits.

    Q.E.D.

    quod erat demonstrandum, which is to say literally, "which was to be demonstrated", and figuratively, "I rest my case".
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Well let’s see what Bob has to say about the increase in resistance and the effect it has on amperage.
    As can be seen by the example that Bob posted above he added half a ohm and the amperage dropped from 23 down to 22.
    The more resistance the less amperage as shown here
    E=IXR
    120 volts divided by 10 ohms equals 12 amps
    120 volts divided by 100 ohms equals 1.2 amps
    It is clear that when the resistance is increased the amperage drops.
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Very true, increased resistance, decreased current BUT, it doesn't take much resistance at high amps to get a fair amount of heat.
  15. Bob NH

    Bob NH In the Trades

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    The amperage drops but that isn't the point!

    The point is that high resistance at a connection in the "fuse box" would cause high heating in the "fuse box", which is the symptom that the original poster observed. That cause would result in high heating even though that high resistance reduces the current in the circuit.

    The original poster was talking about a dryer, that operates on 240 Volts. The fact that the amperage drops with higher resistance at a connection in the fuse box is true but doesn't affect the conclusion because the consequece of that high resistance is to cause heating in the fuse box at the location of the high resistance.

    In fact, if you do the arithmetic you will find that the heating in the fuse box will increase with greater contact resistance in the fuse box until the resistance at the connection reaches the resistance of the dryer load.

    The real fact is that the statement by jwelectric that "Heat means current so the simple answer is something for some reason is drawing to much current." is not supported by the evidence or by any analysis that jwelectric has provided. The "simple answer" is simply wrong!
    Last edited: Dec 4, 2007
  16. bqz

    bqz New Member

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    Well ,Talk with the electrician last night and have decided to upgrade my house from 60amp. service to 100amp. service,do away with the fuse box all together and put in new box with breakers.
    I think it will help when I go to sale the place.
    From what everyone tells me it has to be upgraded anyway in order to qualify for FHA loans (if someone wants to buy it that way).
    Dryer was hooked up right.
    Think problem was running two appliances at same time(dryer and stove both 30amp.) along with everything else,perhaps just pulling too much on that old 60amp.system,I know it should be able to handle it but the house was built in the 40's so I reckon it's a little tired.
    Thanks for input fellows.:)
  17. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Location:
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    Bob
    With the highest respect for you and your profession I must strongly disagree with your findings.
    You made this statement;
    This cannot be a correct statement as when there is an increase in resistance the amperage will drop. Ohm’s law backs this and Ohm’s law is always correct.
    I think what you meant to say here is that arcing due to a lose connection will cause a breaker to increase in heat.
    As with a gas welder the acetylene will not do much by itself but add a little oxygen and the heat is a lot greater.
    Did we start using more acetylene? No. We only added oxygen to the formula.
    This is the same in an arcing event. The ionization of the atmosphere around an arc is what causes the heat not more resistance.
    I believe if we read the original post again we can easily find that the problem is without a doubt something that he did in his installation.
    As can be seen the use of a three wire receptacle makes the installation non compliant. The fact that only half of the overcurrent device is opening says a lot in and of itself. The heating element of a dryer is 240 volts while most dryers have a 120 volt motor therefore the heat will drop out while the motor is still running.

    The fact that one overcurrent is tripping and the main overcurrent is heating up leads me to believe that something is wired improperly which is causing a high current draw. If the heat was limited to only one overcurrent device I might agree that a lose connection might be the problem as the arcing would only affect the area of the lose connection and not the entire system.
    Now back to my original post;
    and this is the only thing that will cause the heating in more than one overcurrent device in an improperly installed circuit.
    First if the dryer was on a three wire receptacle it was not hooked up right.
    Are both the dryer and stove on the same circuit?
  18. bqz

    bqz New Member

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  19. jwelectric

    jwelectric Electrical Contractor/Instructor

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    North Carolina
  20. bqz

    bqz New Member

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    I will make the electrician aware of it.
    Thanks again for everyone's help.:)
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