Small Ground array- off-grid connection to house

[Trailpower]

Hello everyone. I am installing a small 'off-grid' powerstation-based system that will run independently from my 13kw grid-tied system. I could use some advice on safely running PV power into my mechanical room where my 4kw Anker 767 and critical loads panel are parked.

Scenario:

• I have a pair of 480w panels on a small ground rack. I will be running them in parallel due to the 60V limit of the Anker 767.
• I am planning to mount a combiner box on the rack, and from there, run a 6AWG line in buried conduit to the house.

Five specific questions...

1. Is the welding lead/battery cable sold by WindyNation and Temco good for buried conduit? If not, whats the most cost-effective solution?
2. Do I need a shutoff switch on the house exterior, separate from the disconnect in the combiner box on the array? They are about 35 ft apart.
3. What is the correct way to pass the 6AWG line from the exterior through the interior sheetrock in my mechanical room?
4. What is the correct way to run the 6AWG along the wall of my mechanical room, and how to terminate and transition to XT6?
5. Is it appropriate to install a grounding rod next the two panels? Or do I need to run a ground back to the house?

Thanks in advance.

 

[RLM4JC]

I am not a professional electrician or solar installer, however will take a stab.

I used 8awg cable for all my runs and they are all over 250 feet. The voltage loss is minimal. For your application at 35 feet, 10awg would suffice. Here is a link to a chart for cable sizing.

Choosing the Right Wire Size

Choosing the right wire sizes in your PV system is important for both performance and safety reasons. If the wires are undersized, there will be a significant voltage drop in the wires resulting in excess power loss. In addition, if the wires are undersized, there is a risk that the wires may...

www.windynation.com

Welding cable is cheaper. Always stick with 100% pure copper. Welding cable in my experience is hard getting through conduit because of the soft outer casing and can be "sticky" on longer pulls. You can use welding cable, however for the pull depending on any turns and the the size of the conduit I would recommend cable lube. I used 2" conduit for my ground mount runs and for me was the best size for 6 pairs. Thhn cable is designed to be pulled and you can get it at any big box home store. Some PV wire is rated for direct burial. Since you are using conduit that's not necessary and it’s more expensive. When I penetrated my home exterior I used fireblock and outdoor silicone to both waterproof and ensure insects don't infiltrate.
If your inverter does not have a DC disconnect for your PV, a DC disconnect isn't a bad idea. Best place for the disconnect IMHO is closest to the array.
I grounded at my array with an 8 foot buried copper rod. If you don't ground, you can get shocked at the panels if any cables get frayed, the sun is out and your body or pet/livestock touches and completes the circuit causing electric shock and potential death.

 

[pvgirl]

For

Five specific questions...

1. Is the welding lead/battery cable sold by WindyNation and Temco good for buried conduit? If not, whats the most cost-effective solution?

You will want to use a wire type that is rated for wet locations such as THWN-2 which can be found at most home improvement stores. Some battery cable has multiple listing and could be rated for wet locations, other battery welding cable is not listed and shouldn't be used.

1. Do I need a shutoff switch on the house exterior, separate from the disconnect in the combiner box on the array? They are about 35 ft apart.

A shutoff at the house would be a good idea, and is required by code to meet rapid shutdown requirements.

1. What is the correct way to pass the 6AWG line from the exterior through the interior sheetrock in my mechanical room?

One way would be to come out the back of your disconnect with metal conduit thru the wall

1. What is the correct way to run the 6AWG along the wall of my mechanical room, and how to terminate and transition to XT6?

In metal conduit. Flexible metal conduit could be used for the last part of the run, right up the xt6 connector.

1. Is it appropriate to install a grounding rod next the two panels? Or do I need to run a ground back to the house?

You will want to run a ground from the house to the panels, to bond the panels, and ground mount. At the house this ground should be tied in to the houses ground system. No ground rod is needed at the panels.