I want to preface this by stating that I’m brand new to anything solar and electrical so I appreciate any help with my questions. And forgive my ignorance in a lot of this.
When it comes to grounding, it's really confusing so don't feel bad.
Paying up to $0.50/KWh at peak times in my area was getting stupid expensive so I wanted to create a small off-grid system as a sort of proof of concept before building something bigger to try to lower bills.
Yup, that's pretty $tupid!
I put together a EG4 6000ex and 2 LifePower4 batteries with 9 locally-sourced used 208W solar panels ($25 each.. decent deal right?). Output from the inverter is being fed through a separate 100A main AC panel--probably overkill I know. But I wanted to be able to use the main breaker as a sort of on/off switch when I’m not using the system. So far through the AC panel, I’m able to L2 charge a PHEV, run appliances (oven, fridge), and run various electronics—such as multiple TVs, computers, etc. I haven’t tried to max out capacity and run everything at the same time yet.
Nice! Lots of power there for a shed, but not so much for a house. A 6Kw split phase is less than 30a on each 120v leg which doesn't go far for most houses that come with 200a on each leg from the utility. Conservation is going to be a "Big Deal" if you want to run the house on a single inverter. Depending on how you split up your loads (more on that later) you may need to get more inverters and batteries to make that happen.
As for the loads, with only 30a on each leg coming from the inverter you need to decide if you're going to A: Split off a smaller load center to just power critical loads that is switched between the inverter and the grid power OR B: If you're wanting to power the whole house from the solar system. Either way that's going to involve interlocks and new AC panels and such. Lots there if you're not comfortable with house wiring. Either way it's going to get expensive, it's just a matter of which way it gets expensive.
Here are my questions:
- How do I properly ground this setup? I’ve watched Will’s videos regarding grounding on his setups but I’m still confused. My setup is completely off grid so no AC input connection. I have ground and neutrals separate in the AC panel. Am I supposed to create a N/G bond in there? I’m assuming there’s already a N/G bond in the inverter. Unless I’m using it wrong, my voltmeter confirmed there’s charge on the ground.
This is where it starts getting confusing because grounding is a pain. If your shed is completely isolated from the grid then it's going to need its own ground rod/plate system connected to the panel, grounding from the inverter and AC circuits to the panel, and creating the N/G bond. Basically everything you'd have to do if the grid didn't exist.
Where it gets MORE complicated is when you go to tie it into the house. Because your main house panel has the grounding rod and N/G bond already you really SHOULDN'T have a N/G bond at the sub-panel (the shed) as to avoid loops.
What you could do is run the backbone lines between the shed and the house ahead of time, coil up the power leads in the dirt and just connect the ground wire to the grounding block in the main house. Don't connect the N/G bond at the shed and just use the house grounding system to ground everything out there.
I don't know what would happen if you left grounding rods and the N/G bond on both panels connected when you started feeding the house. Ground loop?
- is it common to feel some kinda small shock/current when touching an inverter's control panel? I've noticed this on a couple of mornings and its a little concerning.
No, that's not common and it probably means the grounding screw on the inverter isn't actually connected to ground.
- What is the best option for powering the whole house assuming I can expand my system enough to power most if not all of it? I’m currently renting the house I’m in so I don’t want to invest too much into this part of the system. The landlord has already agreed to allow me to add what is needed to run the house on solar energy. Of course, while I’m confident enough to DIY everything on my own thus far, we’ll be getting the professionals to work with anything connected to the grid.
You'd need to talk to someone far more knowledgeable than I about how to manage the grounding in to panels thing, but in theory the easiest way would be a main transfer switch between the incoming grid power and the power from the inverters, most likely between the meter and the main breaker in the house's panel. It's not uncommon and basically the same as people who have backup generators added to their house. You can always call around to electrical contractors that offer free bids and pick their brains about what that would take.
Any advice / suggestions would be appreciated.
Something to keep in mind is wire distance between the house and shed. Most breakers will only (barely) take a 4AWG wire in the terminal which really limits your current capability and voltage drop. As an example when I ran the backbone from my pump house to my cabin the distance one-way was 315ft and the inspector de-rated my breaker to 70a because of the Al wire and the distance. There are tricks to get around that but I'm not too sure how "legit" they are. Something to consider especially for a rental.
Speaking of it being a rental, your landlord may very well require this to get inspected or parts of it done by someone licenced/bonded to avoid future legal headaches. UL listing is handy but the new NEC2020 codes do make things more challenging so take that all into account.
Also consider that with larger batteries and more inverters to feed the house you're going to want more panels (smoking deal BTW) so you need to figure out where and how to mount those.
Just my initial thoughts.
