How to test ground with multimeter
Are your lights flickering? Is your washing machine running slow, malfunctioning, or not working at all?
If your answer to these is yes, then the ground connection within your home is a possible culprit.
Grounding within homes is one of the most important topics you need to take care of.
It isn’t just important for your electrical devices to work properly, but could be the deciding factor between life and death.
This guide presents you with all you need to know about testing ground.
Let’s get right in.
What Is Grounding?
Grounding, also referred to as earthing, is a protective practice in electrical connections that reduces the risks or effects of shock hazards.
When there is proper grounding, electricity discharged from outlets or electrical devices is directed into the ground where it is dispersed.
Without grounding, this electricity builds up in the outlets or metal components of the device and could cause appliances not to work or function properly.
An individual coming into contact with these electrically charged metal components or exposed wires stands a risk of fatal electrocution.
Grounding directs this excess electricity into the ground and prevents all these from happening.
Now you see why it is important for outlets within your home to have proper grounding.
A multimeter is a tool for fixing electrical problems and is sufficient for checking the grounding within your wall outlets.
How To Test Ground With Multimeter
Place your red multimeter probe in the live outlet port, place your black probe in the neutral port, and record the reading. Keep the red probe in the live port and place the black probe in the earth port. If the reading is not the same as the previous test, your house doesn’t have proper grounding.
These will be explained further.
- Step 1: Insert Your Probes Into The Multimeter
When testing for ground within your home outlets, you want to pay attention to how you plug your probes into your multimeter.
Plug in your red (positive) probe in the multimeter port labeled “Ω, V, or +” and plug in your black (negative) probe in the multimeter port labeled “COM or -“.
As you would be testing hot wires, make sure your leads are in good condition and you don’t mix up the leads at the multimeter to avoid damaging it.
- Step 2: Set Multimeter To AC Voltage
Your home appliances run on alternating current (AC) and, as expected, this is the type of voltage your outlets give out.
Now you simply turn your multimeter dial to the AC voltage setting usually represented with “VAC” or “V~”.
This gives you the most accurate reading.
- Step 3: Measure Voltage Between Live And Neutral Ports
Place your red (positive) multimeter probe in the live outlet port and place your black (negative) probe in the neutral port.
The live port is usually the smaller of the two ports on your outlet while the neutral port is the longest amongst them.
The ground port, on the other hand, is typically shaped like a “U”.
Some wall outlets may have their ports differently shaped, and in this case, the live port is usually on the right, the neutral port on the left, and the ground port at the top.
The voltage reading between your live and neutral wires is important for comparison to be done later on.
Take your measurement down and move to the next step.
- Step 4: Measure Voltage Between Live And Ground Ports
Now, take out your black probe from the neutral outlet port and stick it into the earth port.
Note that your red probe remains in the live port.
You also make sure that the probes are making contact with the metal components inside the outlets for your multimeter to have a reading.
Take measurements and move to the next step.
- Step 5: Measure Voltage Between Neutral And Ground Ports
An extra measurement you want to take is the voltage reading between your neutral and earth ports.
Place the red probe into your neutral outlet port, place your black probe in the earth port, and take measurements.
- Step 6: Evaluate Results
It is time for comparison and you will be making a lot of these.
- Firstly, if the measurement between your live and ground ports is close to zero (0), your home may not be grounded properly.
- Going further, if the measurement between your live and neutral ports is not within 5V of or the same as the measurement between your live and earth ports, then your home may not be grounded properly. This means that when there is grounding, if the “live and neutral” test records 120V, the “live and earth” test is expected to record between 115V and 125V.
- In case all these check out, you then make one further comparison. This is to check the level of leakage from the ground connection and determine how good it is.
Get the difference between readings from the “live and neutral” test and the “live and earth” test.
Add this to the reading from the “neutral and earth” test.
If the addition of these exceeds 2V, then your ground connection isn’t in perfect condition and should be looked into.
In this video we explain this whole process:
A further test you may carry out is on the specific ground resistance of your earth connection.
However, this is a whole other topic and you may check out our comprehensive article on testing ground resistance with a multimeter.
Testing Ground Using Light Bulb
To test the ground connection within your home outlet using a lightbulb, you will need a ball socket and a couple of cables.
Screw in the lightbulb and also attach the cables to the ball socket.
Now, ensure the other ends of the cables are at least 3CM naked (without insulation) and stick them into the live and neutral outlet ports.
If the lightbulb doesn’t switch on, then your home isn’t grounded properly.
As seen, this test is not as detailed and accurate as the test with a multimeter.
Testing the grounding within your home is a fairly straightforward procedure.
All you have to do is take measurements between different wall outlets and compare these measurements with each other.
If these measurements don’t tally or stay within the defined ranges, then your home grounding is faulty.
Frequently Asked Questions
How Do You Know If You Have A Bad Ground Wire?
One common symptom of bad grounding in homes is dim or flickering lights. In other cases, the electrical appliances in your home may not come on or function properly.
How many Ohms Should A Ground Wire Have?
The resistance within your home ground connection is expected to be a maximum of 5 Ohms while the most optimal reading is zero (0) Ohms. The closer the resistance reading is to zero, the better the ground connection.
What Can A Loose Ground Wire Cause?
A loose ground connection will cause your light bulbs to get dim or flicker. It also makes electrical appliances malfunction or entirely stop working as there isn’t proper power for them to operate.