Can I have both grid and off grid?

[Ruff]

I am in the country but will still follow NEC code.

I have two objectives.
1. Decrease my dependency / cost of the local electrical coop.
2. Reliable power to essential items in the winter when the ice storms take down the grid.

I plan to install it as an off grid system first and see how much power I use throughout the summer months. I will add solar / battery capacity as needed then move non essential circuits to the grid powered panel that I will power up at a later date.

My two main questions are:

1. How does code address two independent power systems in the same building? Will my electrical coop even allow that? I can keep the circuits separate and easily identifiable as to which power source it has but metal boxes and EMT in the shop side are grounded back to the respective panels.

2. How do I build a grounding system that will not be unhappy?

If I build a true grid tied hybrid system I am required by the Electrical Coop to have a $1,000,000 umbrella policy to connect the inverter to the grid. This may be my best option, but I am exploring the two system approach to avoid this added monthly fixed cost. The insurance company says I have to raise the covered limits of my cars to the highest limit they offer and double the insured replacement cost of the house. This is not a small increase in monthly premiums.

I am an amatuer radio operator and will have three main antennas around the property. They are all more than 200 feet away from the building and will be independently grounded as required by NEC for transmitting tower installations. I know how to DC / RF ground towers and how to isolate the antenna feed cables with lightning protectors coming into the building. I also plan to use a UL listed lightning protection system on the metal building itself that will have roof spikes with braided grounding cables that run to grounding rods at all four corners of the building as well as feeding three rings of grounding wires that circle the building at 50 ft and again at 100 ft radius.

I have spent a lot of time trying to figure out how to tie the grounding systems together without making the CGFI or arc breakers unhappy. Ground loops cause RFI and dangerous voltage potential and I do not want that.

I know there are a lot of details I have left out. Some are firm, others are still in the planning stages. Please let me know if my plan is viable or if my plans are all wrong and it is best I just get the insurance and grid tie the inverter and keep things as simple as possible.

Jeff

 

[ricardocello]

1. How does code address two independent power systems in the same building? Will my electrical coop even allow that?

I'm not sure they should even have a say. But maybe they have contract language as part of their service agreement.
Your AHJ (Authority Having Jurisdiction) will have permitting rules.

2. How do I build a grounding system that will not be unhappy?

One grounding system for everything, no loops. Safety is the top priority.
As long as fault current can make it back to the source, it doesn't matter where it comes from.

If I build a true grid tied hybrid system I am required by the Electrical Coop to have a $1,000,000 umbrella policy to connect the inverter to the grid.

My approach is not to "grid-tie", and never ever back-feed power to the grid (as best possible).
I treat my system as a very large UPS: it is merely a consumer of the grid power at certain times.

To accomplish that, I installed two subpanels off of my main panel with manual generator interlocks connected to 50A inlets.
This is up to code. What I plug into those inlets could be a generator, or my very large rack of batteries and inverters.

In other words, the coop has no say in what I plug in provided no power is fed back and the installation is up to code.
There are many many discussions about this topic on this site.

 

[DIYrich]

Get a sol-ark or 18kpv. It will passthrough whatever you need from the grid to supplement pv/battery. When you are happy, you can disconnect from the grid.

 

[Ruff]

I'm not sure they should even have a say. But maybe they have contract language as part of their service agreement.
Your AHJ (Authority Having Jurisdiction) will have permitting rules.


One grounding system for everything, no loops. Safety is the top priority.
As long as fault current can make it back to the source, it doesn't matter where it comes from.


My approach is not to "grid-tie", and never ever back-feed power to the grid (as best possible).
I treat my system as a very large UPS: it is merely a consumer of the grid power at certain times.

To accomplish that, I installed two subpanels off of my main panel with manual generator interlocks connected to 50A inlets.
This is up to code. What I plug into those inlets could be a generator, or my very large rack of batteries and inverters.

In other words, the coop has no say in what I plug in provided no power is fed back and the installation is up to code.
There are many many discussions about this topic on this site.

For an off grid system the AHJ is me. I do not live in a city and the county has no building codes or inspections. The state has a few rules, but since I am following NEC, I will not run afoul with them.

As for grid tie, the local Electrical Coop is the AHJ. I will need the insurance policy and a net metering agreement even if I do not plan to sell back ( and I NO NOT plan to sell back) and a licensed electrician to inspect / install.

One note about the current state of the property. I am about 1200 feet from road. I had the electrical coop run a buried line from the road and they set a pole with a transformer (and a street light I can turn off or on as I want) with a 200 amp service at the corner of my building site. I have a small one room cabin that we live in while we build the main building and it is grid connected.

In the main building I intend to have an equipment room for the electrical panels, water filters, and server rack that supports the communications equipment (WiFi WAN / LAN / Ham radio and smart hubs for various smart home internet of things, so a single point ground will right outside that room. As for the loops, I need that for building lightning protection.

I am fighting 3 grounding requirements from 3 different codes that all seem to be different. I need electrical power ground, I need radio antenna and tower ground and I need lightning protection ground.

So you are saying to install on & off grid with a selection switch to power from one or the other but not both?

Jeff

 

[Ruff]

Get a sol-ark or 18kpv. It will passthrough whatever you need from the grid to supplement pv/battery. When you are happy, you can disconnect from the grid.

I talked to someone who did that for about an hour or so during initial setup. They said a guy from the coop come by the next day telling him that they detected a feed back on his meter and he was supplying the grid without a net metering agreement in place. I want avoid that.

Jeff

 

[OffGridInTheCity]

I run an off-grid system and use UL certified ATSs + MTS to deliver solar/inverter power to my home circuits. The Automatic Transfer Switches (ATSs) switch to inverter when the inverter is active and back to grid if the inverter goes off (e.g. run out of battery power). As mentioned above, 1 ground - e.g. my inverter AC wiring uses the house ground.

These days, several AIO models will have the ATS (+UPS) built-in.

 

[Hedges]

Grounds all tie together in the building, as has been said.

Would like a zero-export system, possibly zero-export to CT at grid connection. But you say Coop has rules that cost you money.
Consider an interlocked "generator" input to breaker panel for some/most loads. And a 50A "stove", 60A "welder" or other 120/240V 3-wire plus ground plug. You can feed a hybrid (set for zero export) from the grid using that, and feed its output to the "generator" input.

Grounding is good. I have little or no concern about ground "loops". You also need N bonded to G in exactly one place.
Because the SolArk or other hybrid could be unplugged from the welder output, it loses ground connection and the N-G bond it inherited.
Hardware a ground to the inverter, so if unplugged it is still grounded (I don't care that there is a loop when it is plugged in.)
If inverter has dynamic bonding of neutral to ground, typical or mobile inverters, that takes care of it. Otherwise, mount an outlet on inverter that has N and G wired together, nothing else. if you unplug from "welder" outlet, plug into this N-G bonding outlet.

I talked to someone who did that for about an hour or so during initial setup. They said a guy from the coop come by the next day telling him that they detected a feed back on his meter and he was supplying the grid without a net metering agreement in place. I want avoid that.

Configure hybrid to import a small amount, sufficient that it never exports.

Or, don't connect grid to input. Use Chargeverter or similar so grid keeps battery charged. That is an on-line UPS.

 

[Ruff]

I run an off-grid system and use UL certified ATSs + MTS to deliver solar/inverter power to my home circuits. As mentioned above, 1 ground - e.g. my solar wiring uses the house ground.

Sound good. I prefer a simple solution. Just like that ring from all of those movies " One ground to rule them all" ( or something like that)

Jeff

 

[Mattb4]

For an off grid system the AHJ is me. I do not live in a city and the county has no building codes or inspections. The state has a few rules, but since I am following NEC, I will not run afoul with them.

As for grid tie, the local Electrical Coop is the AHJ. I will need the insurance policy and a net metering agreement even if I do not plan to sell back ( and I NO NOT plan to sell back) and a licensed electrician to inspect / install.

...

Typically the electric company has no interest it what you connect downstream of the Service disconnect. The only issue is if you install a device that can parallel with the grid. Back feeding is not permitted and they can spot it pretty quickly these days. Most folks that run Off grid, with grid as backup, use either a whole house transfer switch, breaker interlock kit or a separate critical loads panel from an off grid inverter.

They do make hybrid AIO's that can operate as both off grid and also grid tie (zero export is still grid tie). These types might be problematic if the Co-op should come around and you have not gotten approval.

 

[Tripplett]

Most folks that run Off grid, with grid as backup, use either a whole house transfer switch, breaker interlock kit or a separate critical loads panel from an off grid inverter.

This is how I set mine up. I pulled the actual romex out of the main house panel and landed it in a Square D critical load panel right beside it - hot, neutral, and ground. That panel is fed by an EG4 6000XP AIO inverter. However I do have a 50a circuit from the main panel to the AIO inverter - for pass through power or to charge the batteries from the grid.
No back feeding possible and still have grid charging/passthrough if needed.

That 50a grid circuit from the main panel also bonds the main neutral and ground to the AIO's N & G buss bars. Those are then bonded from the AIO to the critical load panel. Therefore my panels, inverter, etc grounds are all bonded back to the house ground rod.
Also the main house panel then handles the N-G bond for the solar system. One grounding point, one neutral to ground bond.