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Thread: Hot fuse box

  1. #1

    Default Hot fuse box

    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. #2

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    Call someone.

  3. #3

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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. #4
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by bqz View Post
    So the question is does anyone have an idea as to why this would do what it's doing???
    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. #5

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    By the way who installed the dryer?
    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. #6

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    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. #7
    In the Trades Bob NH's Avatar
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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. #8

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    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. #9
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Bob NH View Post
    Excessive heat is often caused by high current through a high resistance contact.
    ????????????????

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

  10. #10

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    One or the other of us are confused. How can you have a "high current" through "high resistance"?
    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. #11
    Sprinkler Guy Wet_Boots's Avatar
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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. #12
    In the Trades Bob NH's Avatar
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    Quote Originally Posted by jwelectric View Post
    ????????????????

    One or the other of us are confused. How can you have a "high current" through "high resistance"?
    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. #13
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Alectrician View Post
    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?
    Well letís see what Bob has to say about the increase in resistance and the effect it has on amperage.
    Quote Originally Posted by Bob NH View Post
    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.
    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. #14
    Retired Defense Industry Engineer jadnashua's Avatar
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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.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  15. #15
    In the Trades Bob NH's Avatar
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    Quote Originally Posted by jwelectric View Post
    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.
    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 by Bob NH; 12-04-2007 at 09:28 PM.

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