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Thread: Hot fuse box

  1. #16

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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.

  2. #17
    Electrical Contractor/Instructor jwelectric's Avatar
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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;
    Quote Originally Posted by Bob NH View Post
    Excessive heat is often caused by high current through a high resistance contact.
    This cannot be a correct statement as when there is an increase in resistance the amperage will drop. Ohmís law backs this and Ohmís law is always correct.
    Quote Originally Posted by Bob NH View Post
    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.
    I think what you meant to say here is that arcing due to a lose connection will cause a breaker to increase in heat.
    Quote Originally Posted by Bob NH View Post
    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.
    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.
    Quote Originally Posted by Bob NH View Post
    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!
    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.
    Quote Originally Posted by bqz View Post
    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.
    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;
    Quote Originally Posted by jwelectric View Post
    Heat means current so the simple answer is something for some reason is drawing to much current.
    and this is the only thing that will cause the heating in more than one overcurrent device in an improperly installed circuit.
    Quote Originally Posted by bqz View Post
    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.
    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?

  3. #18

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    [QUOTE][Are both the dryer and stove on the same circuit? /QUOTE]

    NO! just running through the same OLD fuse box
    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.
    This is my opinion ,not the electricians and I'm not an electrician obviously but if you could see what I have at my house you would say "change that old junk out"

    Regardless I really need the 100 amp.service for selling purposes and if the dryer isn't wired right it'll trip the new breaker won't it??

  4. #19
    Electrical Contractor/Instructor jwelectric's Avatar
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    [QUOTE=bqz;110610]
    if the dryer isn't wired right it'll trip the new breaker won't it??
    Maybe and maybe not.
    The one thing you have pointed out is the use of a three wire receptacle for the dryer. When you change the panel be sure to install a four wire circuit for the dryer and remove the bonding strip in the back of the dryer.

  5. #20

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

  6. #21
    Retired Defense Industry Engineer jadnashua's Avatar
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    Ideally, a CB or fuse is as close to a dead short when not blown or tripped. So, figuratively, if it was say 1-ohm at load, that equates to a high resistance. Since the heating coil of a dryer may only be 15-ohms (a quick guess, but in that order of magnitude), 1 ohm is a big part of it, and the fuse will generate a fair amount of heat.

    High resistance in this case doesn't necessarily mean hundreds or thousands of ohms, which would drop the total current available so much, little heating would occur; even fractions of ohms on a high current circuit will cause significant heating.

    Run the numbers yourself...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  7. #22
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by jadnashua View Post
    Ideally, a CB or fuse is as close to a dead short when not blown or tripped. So, figuratively, if it was say 1-ohm at load, that equates to a high resistance. Since the heating coil of a dryer may only be 15-ohms (a quick guess, but in that order of magnitude), 1 ohm is a big part of it, and the fuse will generate a fair amount of heat.

    High resistance in this case doesn't necessarily mean hundreds or thousands of ohms, which would drop the total current available so much, little heating would occur; even fractions of ohms on a high current circuit will cause significant heating.

    Run the numbers yourself...
    240/15= 16 amps
    240*16= 3840 watts

    Letís add one more ohm of resistance

    240/16= 15 amps
    240*15= 3600 watts

    According to the numbers we lose 240 watts of heat when one ohm is added to the circuit

    Ohmís Law simply states that an increase in resistance is a drop in amperage.

    The heat produced by a lose connection has nothing to do with increased resistance. What causes the heat is the arcing which burns oxygen (an added fuel) which causes the heat not the resistance of the lose connection.
    This is learned in Elec. 101 and you engineers should have this down pat by now.

    This is the very heart of the arc fault debate. The arc fault devices today will detect a line to line arc which results in a low resistance path but do not detect a in-line arc which would be a high resistance arc.
    The line to line or line to ground arc is a low resistance high amperage arc which is easy to detect but the in-line arc is a high resistance low amperage arc which is hard to detect.

  8. #23
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    You don't need an arc to produce heat.

    Using your example, in the original case the entire 3840 watts is being dissipated in the dryer. However, if the resistance in the breaker, fuse contact, or a connection goes up to 1 ohm somehow, 225 watts (15A*15A*1ohm) will be dissipated there, and the remaining 3375 watts (15A*15A*15ohms) in the dryer. 225 watts is a lot of heat for a device to dissipate if it was designed for zero.

    Having said that, the reason for the breaker, etc., to exhibit a 1-ohm resistance, rather than it's designed zero ohms, might well be due to arcing which resulted in the breaker terminals being oxidized.
    Last edited by Mikey; 12-07-2007 at 09:55 AM.

  9. #24
    Retired Defense Industry Engineer jadnashua's Avatar
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    Your electric dryer or a soldering iron (or in this case a corroded connection acting like a resistor) create heat equally as well without producing arcing...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  10. #25
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Mikey View Post
    225 watts (15A*15A*1ohm) will be dissipated there, and the remaining 3375 watts (15A*15A*15ohms) in the dryer. 225 watts is a lot of heat for a device to dissipate if it was designed for zero.
    Yea What he said.

    Iguess if I had been paying attention to what Jim has been saying instead of being so bull headed to get my point across I would have seen that he said the same thing.

    A lesson to be learned; slow down and learn something.

  11. #26
    In the Trades Bob NH's Avatar
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    Quote Originally Posted by jwelectric View Post
    Yea What he said.

    Iguess if I had been paying attention to what Jim has been saying instead of being so bull headed to get my point across I would have seen that he said the same thing.

    A lesson to be learned; slow down and learn something.
    See also Post #12 again. Same story.

  12. #27
    DIY Senior Member BrianJohn's Avatar
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    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 did not read all the post sooo, if this was answered previously WELL IGNORE

    VD, voltage drop. The voltage drop across a connection results in heat due to resistance and current. All which result in Watts (V*I=W).

  13. #28
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Bob NH View Post
    See also Post #12 again. Same story.
    Yes you did but I was so engrossed in adding the total resistance that I wasnít looking at the resistance being in series and also overlooking the drop across each point of series resistance.

    This sometimes happens when we start looking at forest instead of the trees. As one student said on the phone this morning, ďMike was you looking at the picture and forgetting that your nose was in between you eyes and the picture?Ē

    Well I just donít look at my nose every time that I look at something but yes this is exactly what I was doing.

  14. #29
    Moderator & Master Plumber hj's Avatar
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    Default circuit

    If you hear a noise in the main panel, and it is getting hot, you have a loose, or defective, connection somewhere. If it is at or near the breaker it will overheat it and cause it to trip. A miswired dryer would trip the breaker immediately, although it might just affect one side and the other would allow the motor to run, which is why the breaker should be a linked pair so both HAVE to trip at the same time. Installing a 4 wire outlet and pigtail at the dryer would be useless since the wire to the outlet will only have 3 conductors.

  15. #30
    DIY Senior Member BrianJohn's Avatar
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    If you hear a noise in the main panel, and it is getting hot, you have a loose, or defective, connection somewhere.
    Not necessarily

    If it is at or near the breaker it will overheat it and cause it to trip.
    Not necessarily

    A miswired dryer would trip the breaker immediately, although it might just affect one side and the other would allow the motor to run, which is why the breaker should be a linked pair so both HAVE to trip at the same time.
    Not necessarily

    Installing a 4 wire outlet and pigtail at the dryer would be useless since the wire to the outlet will only have 3 conductors.
    Except this is required per the NEC for new installations dating back a few code cycles.

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