grounding question and confusion

[shortcircuit2]

This is why I rarely ever answer these questions. You do not know the difference between a Equipment Ground Conductor and a Ground Electrode Conductor. The # 10AWG EGC you are referring too is not an EGC, it is a GEC and not covered by 250.122 which is determined by the breaker size. EGC clears ground faults on circuit conductors. EGC clears high voltage from lightning and over head high voltage lines. The GEC is covered by 250.50 through 250.64, and installed in accordance with 250.60. Running it in conduit is a big No-No unless special precautions are strictly followed.

Sunking...I respectfully disagree. The #10 EGC the OP is discussing is for equipment grounding at the array. He did point out that he was using a Sunnyboy 3800 which is a string inverter, and therefore no GEC is needed at the array, only at the inverter.

If he said he was designing a Micro-Inverter type array, then he would need an GEC run to the Array.

Also when you upsize portions of a circuit for voltage drop, you must upsize the equipment grounding conductor also. So just referring to the breaker size, does not allways dictate EGC sizing.

Running the GEC in conduit is common practice in the industry, but in ferrous raceways there are certain bonding requirements.

shortcircuit

[Sunking]

A #10 equipment grounding conductor according to table 250.122 at the strings is generally of sufficient size because string wiring is usually #10, but some inspectors require #6 because they feel it may be exposed to physical damage according to 690.46 onto 250.120(C)...I would recommend #6 solid because grounding is so important up there where it is exposed and it is expected to last 20+ years. The NEC is a minimum standard.

This is why I rarely ever answer these questions. You do not know the difference between a Equipment Ground Conductor and a Ground Electrode Conductor. The # 10AWG EGC you are referring too is not an EGC, it is a GEC and not covered by 250.122 which is determined by the breaker size. EGC clears ground faults on circuit conductors. EGC clears high voltage from lightning and over head high voltage lines. The GEC is covered by 250.50 through 250.64, and installed in accordance with 250.60. Running it in conduit is a big No-No unless special precautions are strictly followed.

[shortcircuit2]

I want to make sure when I install my system (planned for next weekend) that I do the grounding properly. I am installing 24 canadian solar 250 watt panels (two strings) on a flat roof building using the ecofoot ballast mounting system. My inverter is a sunnyboy 3800.

For grounding I was planning on doing the following below. Please let me know if this makes sense.

Use continuous length of 10 gauge bare copper wire on each string and have these separate ground wires terminate onto a ground bus bar in a combiner box on roof. A separate 8 gauge thwn green stranded wire will leave combiner box and go down through conduit to a dc disconnect where ground wire terminates onto a grounding lug. Then separate 8 gauge thwn grounding wire goes through conduit and terminates onto one of the ground terminals (ground symbol without circle around it) inside the sunnyboy inverter. Then from other ground terminal inside sunnyboy inverter (ground symbol with circle around it) 8 gauge thwn through conduit to AC disconnect where there is grounding bar. Then another length of 8 gauge thwn through conduit to ground bar in electric service panel.

Does this make sense?

Also, I am confused by the two grounding terminals in the sunnyboy inverter. One with the circle around it and one without. Is it correct to connect the ground wire from dc disconnect to the terminal with the ground symbol without the circle and to connect the ground wire that goes to the ac disconnect and then service panel to the terminal that has the ground symbol with the circle around it.

A #10 equipment grounding conductor according to table 250.122 at the strings is generally of sufficient size because string wiring is usually #10, but some inspectors require #6 because they feel it may be exposed to physical damage according to 690.46 onto 250.120(C)...I would recommend #6 solid because grounding is so important up there where it is exposed and it is expected to last 20+ years. The NEC is a minimum standard.

All grounding in the string inverter should be common. I don't know why there are separately identified terminals. Do a continuity test to see if they are in common.

Be careful when running the grounding electrode conductor from the string inverter thru "conduit" as you have detailed. If the conduit is metal then it needs to be bonded everywhere the GEC enters and exits that conduit per 250.64(E)

If the grounding electrode conductor is run under NEC article 690.47(C)(3) as a combined GEC/EGC, then your method of terminating at the bus-bar of the service panel is acceptable. Note: Some state incentive programs do not allow this method of grounding (MASS) to be used.

I like Naptown's method of irreversible connecting the GEC to the buildings GEC. The grounding electrode conductor is the only wire that must be unbroken (irreversibly spliced) in the system grounding.

All references per 2011 NEC

shortcircuit

[Naptown]

Nope
One continuous #8 min or #6 preferred to run and bond to each module and run continuously to the combiner inverter and terminate on the building grounding electrode conductor any splices need to be of a type that is irreversable (crimped)

[mikael6]

I want to make sure when I install my system (planned for next weekend) that I do the grounding properly. I am installing 24 canadian solar 250 watt panels (two strings) on a flat roof building using the ecofoot ballast mounting system. My inverter is a sunnyboy 3800.

For grounding I was planning on doing the following below. Please let me know if this makes sense.

Use continuous length of 10 gauge bare copper wire on each string and have these separate ground wires terminate onto a ground bus bar in a combiner box on roof. A separate 8 gauge thwn green stranded wire will leave combiner box and go down through conduit to a dc disconnect where ground wire terminates onto a grounding lug. Then separate 8 gauge thwn grounding wire goes through conduit and terminates onto one of the ground terminals (ground symbol without circle around it) inside the sunnyboy inverter. Then from other ground terminal inside sunnyboy inverter (ground symbol with circle around it) 8 gauge thwn through conduit to AC disconnect where there is grounding bar. Then another length of 8 gauge thwn through conduit to ground bar in electric service panel.

Does this make sense?

Also, I am confused by the two grounding terminals in the sunnyboy inverter. One with the circle around it and one without. Is it correct to connect the ground wire from dc disconnect to the terminal with the ground symbol without the circle and to connect the ground wire that goes to the ac disconnect and then service panel to the terminal that has the ground symbol with the circle around it.