Basic Grid Connect Questions

[Cmy]

I want to add 14K of panels and inverter to a 50'x60' metal building that is 150' from the utility meter. Original owners started with an apartment in the building so it has a small 125 amp CB panel and under ground power line. House was added ten years later, closer to the street, and the under ground line changed to a meter on the house. The meter panel connects to an adjacent, external, 200 amp CB disconnect (picture) and to two 200 amp internal CB panels. The external panel connects to the line going to the metal building.

1. Local utility requires the external disconnect panel be lockable and have an external handle, so I need to change. Looking online, I see fused and not fused, two and three pole, with prices rapidly increasing. Any recommendations for the replacement?

2. Both Sol-Ark and EG4 diagrams show CT clamps at the meter and I want them near the inverter at the building's CB panel. Do they just confirm grid availability or do they measure demand and control the inverter? Hope I don't have to run wire underground back to the panel area.

Better solution to #1 is to change the external meter connection from meter to the internal CB panels, and back up more of the house. Primary goal is lower grid usage with monthly net metering.

 

[Hedges]

CT at the meter lets you limit or zero backfeed to the grid, while allowing inverter to backfeed up to 100% of loads on the property. Located elsewhere changes what it can monitor and limit.

Your exact configuration of meter, main breaker, breaker panel, including busbar current rating of breaker panel affect what you can install. If you have a main breaker without breaker panel, followed by a breaker panel with its own main breaker, you have greater flexibility in terms of how large a PV system can be installed, and automatic/manual transfer of backup loads.

With an AC coupled system you might put GT PV inverter and panels on the metal building. But the lockable disconnect would shut off power to the building. In practice, utility may never do that - only if they suspect backfeed when grid is down. At some point you can add battery inverter closer to the meter.

All depends on what you want to accomplish.

 

[BentleyJ]

If you need zero sell-back then the CT's must be run all the way back to the first utility connection on the 200A breaker in the meter panel shown in the pic. It really doesn't matter where the solar power feeds into the system, the house loads will consume what they need and only the excess will go back to the grid unless the CT's are placed properly and the inverter is programmed accordingly to prevent that.

 

[Cmy]

Excess produced is a gift to the utility - consume more than produced then I pay the difference monthly. They swap meters to one that can net meter. Current bill averages $150 plus meter fee, so wanting solar is more to add property value and help with summer demand. Plus neat thing to do with Texas ERCOT power management warnings. Rather than solar paying for itself, more like an investment that may pay a monthly dividend and has added value to the property when you leave it.

Power during grid outage is secondary but real, so batteries are in the future and need to be in the planning. Have a 9.5kW generator bought after the 'Texas Freeze' but learned from this site I should have gotten a gen/inverter. At least it can charge batteries.