grounding a small DC/AC system?

Hi Todd,

I just finished up a system similar to yours and had to answer the same question.

According to the IEC, you will use the same protective EARTH ground (ground rods, #2awg) for the entire system.  The purpose of this ground is to conduct large static charges/lightning to the Earth instead of your house.  If you have PV panels or a wind turbines mounted up on a roofline or a tower, they should have grounding rods too, preferably close to the base of the mounts - not routed back to the house!

That said, the AC neutral, which is usually tied to Earth ground at the breaker panel/disconnect, should never be tied to the DC ground.  Doing so could create a safety hazard and/or damage your gear.

Also since you have two inverters, you need to have those tied into a single disconnect so that all AC power is disconnected from loads with the flip of a single lever.  The disconnect needs to be located where the fire department can easily get to it in the event of a fire.

For my system (1200W PV/Wind, 2500W AC + DC lighting), I have an AC and two DC disconnects for each source mounted on the outside of my power shed.  Each should be clearly marked.

Maybe more than you asked, but I hope this helps.

-Gregg

Todd
Is there any other ac source in your building, or is the only ac from your inverter ?

Todd
With your PV on a dwelling unit, you should have Ground Fault Protection on it. A common place to install this is in a DC load center.
You should also have a DC disconnect.  Your remote on/off switch for the inverter does not count as a disconnect.

You might want to download the Xantrex manual on PV fault protection, and read it. There are some good diagrams.
http://store.altenergystore.com/Enclosures-Electrical-and-Safety/Miscellaneous-Electrical-Parts/Ground-Fault-Protection/Xantrex-Pvgfp1-Ground-Fault-Brkr-100A-122448V/p2202/
Then ask any additional grounding questions that you may have.

Your current bonded grounding rods can take both the ac and dc grounds.

Yes, your ac neutral should be bonded to ground at some point downstream of the inverter.

I didn't see (and you have not mentioned) any ac overcurrent protection. I am hoping that you have at least an inline fuse, somewhere.

Ken