Dryer keeps blowing fuses

[fhhuber]

According to Ohm's Law (I haven't heard it was repealed.... ), higher voltage would produce lower current.

I'd suspect voltage drops... or the venting.

Higher voltage with CONSTANT RESISTANCE (the dryer heat element) gives higher current.

E=IR works, but E1 =I1 * R1 And E2 = I2 * R2
If R1 = R2 and E1 <> E2 then I1 <> I2

Start plugging in numbers using 1 for E1, R1 and I1 (simplest numbers) Then 2 for E2... solve for I2.,, and you get I2 = 2 Current went up proportionally to voltage.

Real world the resistance of the heating element varies somewhat with temperature... but its not going to significantly affect the result of excess current making it hotter.

That's why feeding 110V to a 220v light bulb (yes they make them) works and gives you half the wattage (and the bulb will last for many many years), but feeding 220 to a 110 rated bulb will burn out the bulb in half a second.

************

Thermal fuse should be protected by the dryer's thermostat... which should shut off power before the fuse blows. The fuse is fire prevention. the thermostat is temperature regulation.

Even with a plugged dryer vent AND a power surge the thermostat should shut off power to the heater before the fuse blows.

I expect that has a 3 setting thermostat... and its failed.
Since you replaced that ...Did they change the part number from original? if they did there's your problem with the replacements. Not the same part, not working the same as the original.

BTW.. I used to be a Whirlpool service tech.

 

[bigdee]

Hi Tim. You&#146;re on the right track. Remember that the only thing constant is the machine&#146;s opposition to current flow (ohms). Power (watts) is not a fixed value, but is a result of how much voltage you apply. You&#146;ve recognized the difference in the 2 formulas that results in the power rising exponentially as the voltage rises. If you double the voltage, you get double the amps and get a result of 4 times the watts. On 240 volt circuits, utilities (around here) are allowed a tolerance of plus or minus 10 volts, but sometimes stuff happens and the voltage rises beyond that.

If the dryer&#146;s design spec is 28 amps at 240 volts, its resistance must be 240/28 = 8.57 ohms
The manufacturer&#146;s design wattage at 240V = V x A = 240 x 28 = 6720 watts

The same machine having a resistance of 8.57 ohms when an increase to 250V is applied:
A = E/R = 250/8.57 = 29.17 amps
Wattage produced = V x A = 250 x 29.17 = 7292W (a 572W increase or 8.5% above manf design spec)

The same machine having a resistance of 8.57 ohms when an increase to 260V is applied:
A = E/R = 260/8.57 = 30.34 amps
Wattage produced = V x A = 260 x 30.34 = 7888W (a 1,168W increase or 17.4% above manf design spec)

- Grandad

Factor in the inductance of the electric motor and this formula goes out the window. Ohms law only works with resistance of the heating element. Also the dryer motor operates at 120 volts, not 240!

 

[Grandad]

Factor in the inductance of the electric motor and this formula goes out the window. Ohms law only works with resistance of the heating element. Also the dryer motor operates at 120 volts, not 240!

Hi bigdee. Yes, we could complicate this further by including inductance, but as I said in post #12 above, the current draw of the motor is insignificant compared to the current draw of the elements. So, in my opinion, the formula is valid. - Grandad

 

[Woodonglass]

Factor in the inductance of the electric motor and this formula goes out the window. Ohms law only works with resistance of the heating element. Also the dryer motor operates at 120 volts, not 240!

Every electric dryer I've ever seen operated off 220 volts!!!!

 

[bigdee]

Every electric dryer I've ever seen operated off 220 volts!!!!

Look closely at that picture it is written 125/250 volts. Heating element is 240 and motor is 120! There is a neutral.