How to Fix an Inverter Overload Fault

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Having an off-grid power system can give you a feeling of independence and allows you to live comfortably without sacrificing your comfort.

But as with most things in life, it also has its challenges.

One of the more common problems you may experience when using an inverter is an overload fault.

Sometimes fixing it is straightforward while other times it is not.

In this guide, I’ll walk you through some tips to identify possible causes of the inverter overload fault and how you may go about fixing them.

Quick answer: If your inverter shows an overload fault, as a first step, you can check the external connections to the inverter as this usually solves most overload fault problems. Has an appliance with a high draw current been connected?

Does any of the connected appliances have a high surge current rating that exceeds what the inverter can handle?

Read on for what else can cause inverter load faults and how you may be able to fix it.

6 Common Causes of Inverter Overload Fault (+ Fixes)

#1. An appliance with a high continuous draw or surge current that exceeds what the inverter is designed for may have been connected to the inverter.

Fix: Check If any high draw appliance such as a water heater, air conditioner, or kettle has been connected to the inverter that may have caused the fault and disconnect it.

Make sure that the recommended current draw of the inverter is not exceeded.

#2. An appliance with a surge current that exceeds the inverter’s handling capability such as a fridge, or a dishwasher can also trigger the overload fault.

Check: Might you have just switched on an appliance with a motor whose surge current draw may have triggered the fault? If so, you should disconnect it and look for an alternative power supply to prevent the high current draw situation.

Examples of appliances to watch out for are: fridges, washing machines, and dishwashers.

You may need to reset the inverter afterward for the fault to clear. Consult your inverter’s owner manual for how to do this.

#3. A fault in one of the connected appliances, such as a short-circuit can also trigger the inverter overload fault.

Fix: Inspect each of the connected appliances, one at a time for any signs of burning or overheating. If found, disconnect, reset and check if the fault clears.

You may need to reset the inverter afterward for the fault to clear. Consult your inverter’s owner manual for how to do this.

#4. Do you have an inverter charger system? Is your expectation that the appliances powered when the grid is available should be more compared to when the inverter is in backup mode?

If the appliances are connected to the inverter output then the maximum power draw available will still be restricted by the maximum power handling of the inverter.

Fix: Connect the high draw appliances on a separate circuit directly to the grid such that when it is down, the appliances are not powered by the inverter backup power.

You may need to reset the inverter afterward for the fault to clear. Consult your inverter’s owner manual for how to do this.

#5. Additionally, a short-circuit in the cabling, perhaps the cable is damaged and wires are short-circuited can also trigger a short-circuit.

Fix: Inspect the cabling and once the damaged section has been cleared or repaired, you may need to reset the inverter.

Consult the inverter’s owner manual for how to do this.

#6. A short-circuit in the inverter can also display the overload fault condition. If all the above fail, you may have a fault in the inverter.

Trying cycling power off and on to try to clear this fault as a power surge may also cause this fault.

If it persists then consult a qualified technician.

Step by Step Guide to Locate the Inverter Overload Fault

To narrow down what could be causing the problem, we go through a series of tests step by step in this order:

  • Inverter test
  • Appliance test
  • Cabling test

Inverter test: How to test that the inverter is not the source of the overload

1. Switch off the inverter
2. Make sure that the inverter battery is fully charged
3. Check that the battery terminals are clean and cables from the inverter are firmly secured to the battery
4. Disconnect all appliances – by unplugging from the inverter GFCI sockets if plugged directly or by switching off the circuit breakers
5. Switch on the inverter and check if the overload condition is still there. If the overload error persists, press the reset button on the inverter if it has one or switch it off and then on again.

If the overload error persists, quite likely, there is a problem with the inverter – possibly a shorting electronic component.

This can explain the fault condition of an inverter showing an overload even when there is no load connected!

Next, let’s test whether the connected appliances are the source of the overload.

Appliance test: How to test that the appliances are not the source of the overload

1. Confirm that the total power consumption of the connected appliances does not exceed what the inverter can handle.

If necessary, connect one appliance to the inverter at a time starting with a low wattage appliance like a study lamp.

2. Check that the appliance’s surge power rating does not exceed what the inverter can handle.

3. Could the appliances be faulty? Faulty appliances with a short-circuit can also trigger an inverter overload fault when connected to the inverter

So check – do the appliances work with shore power or grid power without any problem? If they do, then there is no fault with them. 

If they don’t work properly, get another known working appliance and use it to test with the inverter.

Lastly, let’s test that the cabling is not the cause of the overload

Cabling test: How to test that the cabling is not the source of the overload

It is possible for faulty cabling to cause an inverter overload fault,  for example, if there is a short-circuit in the cabling.

To rule out faulty cabling, with the inverter running smoothly, disconnect the appliance leaving the cabling from the inverter alone. 

If there is a fault in the cabling, the inverter overload error will occur.

Signs that an inverter is overloaded

#1. Inverter shut down

Modern inverters have an overload protection feature. If the rated power of the inverter is exceeded, the inverter usually shuts down.

Depending on the inverter design, the internal breaker can trip to disconnect the high draw appliances and avert damage to the inverter circuit.

#2. Inverter may fail

This really depends on the quality of build of the inverter, some inverter’s protection is overhyped, does not work well and the inverter can fail in the process.

With good quality inverters, typically a breaker will trip and may need to be manually reset or reset itself once the overload has cleared.

#3. Overload fault LED with Continuous beep or buzzing sound

Additionally, the inverter usually displays an overload fault LED, and may also make a continuous beep or buzzing sound to draw attention to the overload condition.

How to Protect Your Inverter from Overload?

Consider, installing a fuse of the appropriate rating depending on the inverter capacity (watts) on the positive wire from the battery terminal to the inverter as an added layer of protection.

How to size the inverter protection fuse. Note: This is a rough guide

Formula

Inverter fuse rating = (maximum continuous rating of the inverter in watts/inverter efficiency) x 1.25

For a 1000 watt/ 12V inverter, estimated fuse rating = (1000/12) *1.25 = 100 A. You can use the standard fuse size closed to 100A.

Related Questions

Why an Inverter may be Showing Inverter Overload Fault with no Appliance Connected?

If the inverter shows an overload when no appliance (double-check this as it is possible for some appliances to remain connected) is connected then there is likely an internal fault in the inverter.

You can try resetting it (check the inverter manual for how to do this).

If the fault persists then you need to have the inverter checked out by a qualified technician.

Final Thoughts

In summary, if the inverter displays an overload fault, check if any of the appliances may be causing the overload.

They might be drawing excessive power or be faulty.

Other possible causes of an overload fault include damaged appliance cabling, an inverter fault, or a temporary glitch caused by a power surge that may clear after resetting the inverter.

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