An inverter can operate without being grounded and will thus be a potential hazard to users as it can cause a nasty, even fatal shock. An ungrounded inverter will contain live points, which, when touched, will send a current through your body to the earth. Your body has completed the loop to earth.
Inverters should always be grounded to a single grounding point. A copper grounding rod must be driven into the ground outside and connected to the single grounding point using a thick copper grounding wire. The electrical distribution panel is ideal for having a single grounding point.
You must understand the differences between the following ground points used in Inverter installations:
- Inverter Enclosure Ground Terminal.
- The grounding terminal of the AC terminal bus bar.
- Neutral grounding connection inside an electrical breaker panel box.
- Earth groundwater copper pipe, copper grounding rod, or battery negative terminal
The National Electric Code for all AC distributed electric wiring requires that the AC source supplies the Neutral Ground connection. Let’s review why proper grounding is of the utmost importance to your safety.
What Is A Ground Fault Protection Circuit?
Ground fault detection (GFCI) will cause the AC power to trip when it detects unequal currents flowing through the positive (live) and neutral conductors. The fault detection assumes that the current flow is because the electricity has found an unwanted path to the ground.
If you accidentally touch a live wire connection, an ungrounded inverter will send the AC through your body. This can be very unpleasant and potentially fatal.
A ground fault detection circuit will cause the AC power to be cut when as little as five milliamps of differential current flow to the ground. It will also trip when you wire an unwanted path to the ground.
What Should Be Ground on Your PV System
All the components in your system should be grounded to the same single-point grounding connection, except for a ground-mounted solar array. If the components were all individually grounded, this could lead to voltage potential differences.
The AC output terminals of the inverter supply the Neutral to Ground connection, and no secondary grounding connections are permitted.
Ground Fault Detectors
The ground fault detectors do not need a ground wire connection as they sense differential current between Hot and Neutral. Ground wires are there to prevent equipment enclosures from becoming energized.
The user must keep all Neutral wires separated from any Ground connections. The AC Breaker Panel Neutral Bus Bar bonding screw is not tightened to connect with the Breaker Box.
And never put jumpers from Neutral to Ground wires in electric outlet boxes.
How Is The Inverter Grounding Done Correctly?
Inverters are enclosed with an Aluminum heatsink to dissipate heat and are also fitted with a grounding terminal to the enclosure. A grounding wire of 6 AWG must be connected to the grounding terminal on the inverter and connected to a single-point grounding connection wire.
If there is no suitable grounding connection point, then the grounding wire from the inverter must be connected to the negative terminal of the battery bank for off-grid systems. For Grid-tied systems, the inverter grounding is more complex and should be done by a qualified electrician.
Some modern inverters are fitted with a grounding point connection in the inverter circuitry. Still, this grounding point must be disconnected when the inverter is connected to a power distribution panel with its grounding.
Double Grounding Problems
The inverter must not be double grounded as this may cause a problem. The grounding for grid-tied systems will vary in different countries and states and is determined by local codes.
The installation and grounding of inverters in grid-tied applications should always be done by a qualified electrician and under the prevailing code. The inverter manufacturers will advise on several options in the insulation manual.
Still, it is up to the electrician to select the method that will comply with the code in your area.
Grounding Systems For Off-Grid Inverters
The grounding of inverters in off-grid installations can be critical to the safety of the users and the connected AC-powered devices. Correct grounding in a sailboat is even more complex as land-based installations have no grounding.
Incorrect grounding can lead to the potential of electrocution and may even contribute to the corrosion of metal parts on the boat. A qualified expert must always do such complex electrical installations.
In off-grid cabins or RVs, the DIY options are less risky, but the installation instructions of the inverter manufacturer must be followed to the letter. In RVs, the grounding connection must be connected to the vehicle’s chassis via a good contact point.
In the case of off-grid cabins, the grounding must be done by driving a copper spike into the ground outside the cabin and connecting the spike to the electrical distribution panel for the cabin.
- The inverter and all connected appliances and devices will also be connected to the single connection point of the distribution panel. It is always advisable to verify the electrical installation by a qualified electrician.
Even small off-grid power inverters have the potential to impart a fatal shock. This is even truer when the proper grounding of the inverter has been affected. Electricity always looks for a path to follow to dissipate the electrical charge.
A ground wire ensures that the path of lowest resistance in the event of a short circuit will always be to earth, thus eliminating the risk of flowing through the body of someone touching a live connection by accident.
Most household fires are started due to electrical short circuits and the incorrect grounding of the electrical system. It is admirable that DIY enthusiasts attempt the installation of power systems by themselves.
Still, they should not allow the system to be switched on without prior inspection and certification by a qualified electrician.