A rooftop solar system puts metal structures, long cable runs and sensitive electronics on the highest, most exposed part of a building. Good earthing protects the people who maintain it, the inverter that converts its power, and the building below. It is also one of the first things an inspector or DISCOM engineer checks.
What has to be earthed
- Module frames and mounting structure. Every metal part that a person could touch should be bonded together and connected to earth. Bonding clamps or jumpers across joints keep the path continuous.
- The inverter. Its body is earthed as the manufacturer’s instructions require.
- Surge protection devices (SPDs). SPDs on the DC and AC sides need a short, direct path to earth to work properly.
- Lightning protection, where provided. An air terminal above the array needs its own down conductor and earth pit.
How many earth pits?
It depends on the size of the system and the design, but small rooftop systems commonly have separate pits for the array structure and DC side, the AC side, and the lightning arrester, all bonded together below ground. Larger systems need more. Follow the designer’s drawing and the requirements of your DISCOM and any subsidy scheme you are using.
Why chemical earthing suits solar
Solar earth pits are often dug wherever there is space near the building, in dry ground nobody waters. A chemical earthing electrode keeps a steady reading without maintenance. Our BFC Solar Earthing Grade compound is made for these installations and comes in 15 kg bags that are easy to carry to a rooftop site.
Running the earth conductors
- Use a conductor sized for the fault current the designer has worked out: G.I strip, copper strip or flexible copper cable, as specified.
- Keep runs as short and straight as you can. Sharp bends and long loops make surge protection less effective.
- Fix conductors properly along the roof and walls with saddles, so wind and maintenance work do not pull them loose.
- Make every joint with a proper clamp or lug. Twisted wire and loose bolts are a common cause of failed tests.
Lightning protection over the array
Whether a rooftop array needs a lightning arrester depends on the building, its height and the risk assessment. Where one is fitted, place it so its shadow does not fall across the modules for long, keep a safe separation from the array, and give it its own down conductor and earth pit. Our lightning protection range covers ESE and conventional arresters, masts and strike counters.
Common mistakes
- Using the building’s existing earth pit without testing it first.
- Leaving some module frames unbonded because the clamps “touch anyway”.
- Running the earth conductor alongside or coiled with power cables.
- Burying the pit without a cover, so it can never be tested again. A pit cover costs little and saves a lot of digging.
Test before handover
Measure the resistance of every pit and check continuity from each array section to earth before the system is commissioned, and record the values. An earth tester and a qualified electrician are all it takes, and the readings are your reference for every future check.
Frequently asked questions
Can a solar system use the building’s existing earth pit?
It can be bonded to the building’s earthing, but test the existing pit first, and follow the designer’s drawing. Dedicated pits for the solar system, bonded to the building’s earth, are common practice.
Does a small rooftop system need a lightning arrester?
It depends on the building, its height, its surroundings and the risk assessment. Ask your designer; where one is fitted, it needs its own down conductor and earth pit.
Which backfill compound should be used for solar earthing?
Our BFC Solar Earthing Grade is made for solar installations and comes in 15 kg bags that are easier to carry to rooftop and remote sites.
We supply complete solar earthing material: electrodes, BFC Solar Earthing Grade, strip, module clamps, lightning arresters and pit covers. Send us your system size and layout for a quotation.