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How to Test a Heating Element

This is a general guide to test any type of heating element for failure using an multimeter to measure the resistance of the element.

Steps

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    Assuming that a visual inspection of the element has been done or isn’t possible.
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    First we need to know what the resistance of the element should be this can be calculated using known values:
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    R = (V x V) / P [Where V is the voltage powering the element, P is the power the element uses and R is the resistance.] (An example calculation is shown in the tips section)
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    Now we Know what resistance we are looking for we can check the element.
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    Set the multimeter to the resistance setting with an appropriate measuring scale selected.
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    With the power off, Unplugged or by other means disconnected from the mains. Measure the resistance of the heating element by connecting the multimeter leads across the terminals of the heating element.
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    If the reading is the same or very close to that of the calculated value then the element is OK and the fault lies elsewhere.
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    If the reading is a lot higher than the calculated value the element is failing and won't be heating fully.
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    If the reading is a lot lower than the calculated value the element is failing and will be heating to much or not at all if part of the element has shorted or exploded.
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    If you are checking the heating element in a hot water heater in a house. You will need to disconnect it from the power source, in most cases it will mean locating your breaker panel and turning the breaker off.
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    Next you will need to drain the water from the water heater. Locate the water valve at the bottom of the water heater. Attach a garden hose to it securely, the open the valve. You will notice a relief valve near the top of the water heater, you can flip the handle up to open it. By doing this it will allow air into the tank causing the water to flow out more quickly.
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    Once the tank is empty, you can now remove the cover over the heating element.
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    Now remove the electrical wires going to the heating element.
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    Next you will need a socket or a wrench, if you have access to get to it. Remove the heating element, you can now check the element as shown above.

Tips

  • Lets take an 800W kettle as an example:
  • V = 230V (UK mains voltage),
  • R = (230 x 230) / 800 = 66.1 Ohms
  • P = 800W,
  • If you don’t know the value of the voltage used by the element you could measure the voltage between the terminals of the heating element with the device powered and on.

Warnings

  • Note: Take care when dealing with electricity. If you're not confident in your ability to work with electricity then don’t do it. Ask some one who is, such as an electrician or an electrical engineer.

Things You'll Need

  • Multimeter or Ohmmeter and Voltmeter

Article Info

Categories: Electrical Maintenance