How to Test a Heating Element

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How to Test a Heating Element

Many devices use a heating element to convert electrical power into heat. These devices include hair dryers, coffee makers, dishwashers, and electric kettles. Heating elements wear out easily, and may need replacing several times over the life of an appliance. It is fairly easy to remove and replace a heating element, especially on larger appliances such as water heaters. Before going through the expense and effort of replacing one, however, it is a good idea to test the heating element to be sure it is the part of the appliance which is causing the problem.

 

How a Heating Element Works

A heating element is made of a coiled wire which conducts electricity. It functions by resistance; when passing through the wire, the electricity encounters resistance, which causes the wire to heat up. A heating element also includes sensors and fuses. A sensor gauges the temperature of the element, and when it gets too hot the sensor cuts off the power supply for a period of time, until the coil cools back down. In this way a heating element can sustain a particular temperature range over an extended period of time, for example to keep liquids warm in a coffee pot. A fuse cuts power completely, if the element malfunctions and gets too hot or overrides the sensors. This keeps the element from starting a fire. When testing a heating element, first determine if the problem is truly in the element itself or elsewhere in the electrical system. The repeated failure of a heating element, after it has been replaced, is often a sign of a larger electrical problem.

 

How to Test a Heating Element

Only individuals knowledgeable about electricity should perform tests or repairs. Those uncomfortable with electricity should consider hiring an electrician.

To diagnose a heating element by testing its resistance, take these steps:

  1. Disconnect the appliance from the power source to avoid the risk of an electrical shock.
  2. Use a multimeter. A multimeter measures electricity in a variety of ways, including voltage, current, and resistance. Set the multimeter to measure for resistance.
  3. Perform the calculation: R = (V x V) / P, where R = resistance, V = voltage, and P = the power the appliance uses. In Australia, voltage in a household outlet is usually 230 volts. Look for power (wattage) on the appliance’s specifications label. For example, a coffee maker might be 600 watts. In this case: R = (230 x 230) / 600.
  4. Connect the multimeter’s leads to the terminals of the heating element. Connect the positive lead to the positive terminal on the heating element, and the negative lead to the negative terminal. Generally, the positive lead on a multimeter is red and the negative lead is black, but this varies, so check the manufacturer’s guidelines for a particular multimeter.
  5. If the resistance readout on the multimeter is close to the R value calculated by the equation, the heating element is working properly. If it is not, the heating element has failed and must be replaced. A readout lower than the calculated value indicates that the element is heating too much. If the readout is high it indicates the heating element is not heating enough.

If the heating element is indeed working properly, but the appliance is still malfunctioning, the problem is probably elsewhere in the electrical system. Check the fuses to make sure they have not blown. The wiring may be bad, either inside the appliance or in the power cord, as is preventing electricity from reaching the appliance.

 

Deciding Whether to Replace or Repair

When deciding whether or not to repair an appliance with a faulty heating element, consider the as-new price of the appliance. A large appliance such as a household water heater or a clothes dryer is expensive, and repairing the heating element is more cost effective than replacing the entire unit. However, most small household appliances, such as coffee makers and hair dryers, are fairly inexpensive and would cost more to repair than they are worth new. In this case, it is not worth the time to most people to replace a heating element.

 

How to Buy Heating Element Testing Supplies on eBay

In the search bar on any eBay page, type ‘multimeter’. A multimeter goes by many names, so also try searching ‘multitester’ or ‘VOM’ (which stands for ‘volt-ohm meter’).To find heating element replacements, search eBay for elements for a variety of appliances, including water heaters and clothes dryers. eBay also has resources to find tools, wiring, and other electrical components.

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