Grounded PV systems

[Isetech]

Grounded PV system

When would you ground your positive or negative on a PV systems?

How do you know if your inverter has ground fault protective devices built in?

Would you use a fuse on both the negative and the positive terminals if your system is grounded?

Do you need a DC isolator if your DC combiner box is located in the same room as the inverter (with a DC isolator)?

[GCE]

Grounded PV system

When would you ground your positive or negative on a PV systems?

Generally it is the thin film panels that you would earth the neg leg - The inverter would then have a setting for neg earth otherwise it will pick up a ground fault
Manufacturers specifications on the panels and inverters will determine the decision

How do you know if your inverter has ground fault protective devices built in?

I understand that most have - It will be in the specification

Would you use a fuse on both the negative and the positive terminals if your system is grounded?

Manufacturers spec will inform you

Do you need a DC isolator if your DC combiner box is located in the same room as the inverter (with a DC isolator)?

In my opinion , yes

SANS 10142-1
6.16.1.4 The disconnecting device shall be positioned
a) within 1,5 m from the appliance, or
b) in a distribution board (if the switch-disconnector is capable of being locked
in the open position).
Even where a disconnecting device is on the appliance, a separate
disconnecting device shall be provided in the fixed installation to allow for the
total removal of the appliance.

[Isetech]

I dont believe that your refence to 6.16.1.4 is correct. We are referring to the solar panels (an energy source), I wouldn't call them an appliance.

The Sunsynk inverter for example has a DC isolator on the side or below the inverter. The equipment in the "DC combiner box" has surge protection, fuses and a DC isolator.

I would think you would need to have accessible isolator, like a fireman's switch for high voltage signs, considering these solar panel are capable of producing 1500 VDC. It doesnt make sense having a switch disconnector next to the inverter locked in a garage, outbuilding or inside the house.

Its like mounting a lithium battery below 1.5m in a garage (especially in front ) used to park motor vehicle and people say mounting them in the bedroom is stupid.

[Justloadit]

ONLY EARTH PV terminals if the specific inverter user manual says so.

Some inverters have a common negative terminal, and some have a common positive terminal as a reference for the internal boosting circuits.
Also if you have a Hybrid inverter, invariably the negative electronics reference in the inverter is referenced to the Neutral of the mains and load. Earthing the Negative of the PV panels cables will cause a short between the Negative of the Electronics and the Neutral of the supply, with disastrous results.

[GCE]

I dont believe that your refence to 6.16.1.4 is correct. We are referring to the solar panels (an energy source), I wouldn't call them an appliance.

The Sunsynk inverter for example has a DC isolator on the side or below the inverter. The equipment in the "DC combiner box" has surge protection, fuses and a DC isolator.

I would think you would need to have accessible isolator, like a fireman's switch for high voltage signs, considering these solar panel are capable of producing 1500 VDC. It doesnt make sense having a switch disconnector next to the inverter locked in a garage, outbuilding or inside the house.

Its like mounting a lithium battery below 1.5m in a garage (especially in front ) used to park motor vehicle and people say mounting them in the bedroom is stupid.

If you need to remove the inverter to replace or take for repairs at some stage you would need to be able to ensure that all wiring lying there is safe which is why I would use that particular regulation to ensure that I can lock out

[Isetech]

Its a tricky one because even if you switch off the isolator on the side of a building, it still doesn't make it safe for the fireman. I agree with the isolation to remove the inverter, you need to have the isolator next to the inverter.

After chatting to another sparkie about the AC changeover, We have modified the AC changeover panel and added another double pole isolator to the panel. Now we can isolate the inverter and remove it and still have the bypass back to the essential DB.

Another interesting point someone made the other day, using the different colour lights with the changeover switch creates a minor challenge. We use red for "Grid" and blue for "inverter". If the blue light is on but the system is in bypass, then the light should be red. I dont feel its a big deal because the indicator light will still be showing that there is power. Its just the documentation and wording in the isolation procedures and commissioning sheets.

If you need to remove the inverter to replace or take for repairs at some stage you would need to be able to ensure that all wiring lying there is safe which is why I would use that particular regulation to ensure that I can lock out