Thats a good rule. Unless you have some kind of automatic transfer switch or something. lol
On grid without utility consent.
- Thread starter Electroaliance
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GXMnow
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Technically, the transfer switch means you are not connecting it to the grid.
Hybrid inverters are an odd case as some can work in several different modes. I would always look for the UL listing. UL-1741 covers safe grid tie inverter tech. The main focus of UL is safety. If anything goes wrong, it has to fail in a safe manner.
My battery inverter is a Schneider XW-Pro. It has 2 inputs and one output. The AC-1 input is meant to connect to the grid. This port can export power to the grid when running in grid tied mode. It has a transfer relay built in to connect it to the grid, only when it is safe to do so. If it senses any issue, it opens that relay and goes into off grid mode until the grid looks correct again. And when it does connect to the grid, it obeys the UL rules of monitoring the grid for 5 minutes before it will even try to export any power.
The AC-2 input is meant for a generator. It is strictly an input and can't export power on the AC-2 port. It has another relay for this port, and it only closes when the AC-1 relay is open, the two can never connect to each other.
The output is just what you expect. It is always connected to the output of the inverter and will receive power from the inverter while in the off grid state. When it is in grid tied mode, the output is essentially also tied to the grid through the transfer relay. In my installation, the output can also act as an input, but only for grid tied UL-1741 inverters running in AC coupled mode. My Enphase system is connected into the backup loads panel that is fed from the XW-Pro output. Right now my batteries are full and the Enphase system is producing more power than I am using. The extra power is flowing backwards through the XW-Pro from the Enphase system back out the AC-1 port to my main panel where it powers a few more loads and 2,000 watts are going out to the grid.
I would not even try to setup a system like this with any equipment that is not UL-1741 listed. This setup could be pulling or pushing over 6,000 watts and that is plenty of power to cause big trouble if anything goes wrong.
zanydroid
Solar Wizard
It will function electrically with many of the major safety mechanisms in place and is legal in some jurisdictions but is not legal in any U.S. jurisdiction. Also the U.S. mostly has 120V outlets while GTIs are predominantly 240V
I agree it is mostly safe since the exposed prongs will not be energized when plugging in. And after unplugging the exposed prongs will be safe again within a few seconds so there is a limited window of danger. Which can be mitigated by adding disconnect switches.
Don't need a grid tie inverter or some 6000w inverter to accomplish this. A small 500w inverter to power the load direct from a battery and solar to keep the battery charged. Need enough battery for 48+ hours of use.
Transfer switch will provide grid backup. Or manually flip on a grid powered battery charger if no solar.
Either way no back feed is even possible and the load is covered.
GXMnow
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The main legality issue here in the USA has to do with the back feed into the main panel. By the 120% rule, the back feed breaker must be at the complete opposite end of the bus bar and be clearly labeled as the back feed. So yes, it is most likely not legal by that rule, but it is still "safe" when used within it's design. They do sell 120 volt units you can plug into an outlet anywhere in the house and it will work and not cause a serious danger. But I do agree, it is best to have the back feed at the end of the bus bar and to know for sure where power is coming into the panel.
There are many things we can do that are completely safe, but do not meet local codes. Most building and electrical codes are intentionally a bit more strict than they need to be because a lot of people don't meet all of the codes. A bit of extra safety overlap is not a bad thing. I always build to code and highly recommend that anyone else does as well. If you build to local code, you know it will be safe and if someone else needs to work on it in the future, they won't find a big surprise. But there are certainly use cases where something may not meet code but is still safe and helps get around a problem.
Here is an example.
My old house back in Illinois only had a singe 15 amp 120 volt circuit for the garage. It was a buried #12 run over 120 feet long. I had planned on trenching and running a 3 x #6 UF cable for a 30 amp 240 volt feed, but I ended up moving before I could do it. My air compressor was on the ragged edge to run on that 120 volt 15 amp feed. I had to even turn off the lights when it would run up the tank pressure. If I was still living there, putting 1,200 watts of microinverters on the garage roof, feeding into that circuit would have been a great help. If nothing was on in the garage, it would feed up to 10 amps back to the main panel in the house. But in full sun, it would have given me a solid 20 amps in the garage so I could run the compressor and a few other tools and lights. Technically, it would not meet code, but it would be safe and work just fine. If I did this, I would move the garage feed in the main panel to the bottom of th bus bars, opposite the main breaker and it would have been under the 120% rule. The only thing that would not meet code is that it is not a dedicated circuit and loads could be on the same branch. In normal use, the current demanded on the wires from the house to the garage is greatly reduced. The current is never more than it was originally planned for, but some times, the current might go backwards. To make it as safe as possible, I would run a sub panel in the garage, and the outlets would have been on 15 and 20 amp breakers still. When the sun is shining, I could get 25 amps into the panel. Th breakers would be sized to protect their wires.
At my new house here in California, the codes are even a bit more strict on some things, but far looser than Chicago on others. I am thinking of adding a gazebo in the back yard with a solar panel roof. To strictly meet the code, I would need a dedicated feed from the PV solar equipment back to my main panel in the garage, and if I wanted lights or outlets, it would need a separate dedicated feed back from the main panel out to the gazebo again. This seems like a complete waste of wire and money. Yes, if you don't add the proper breakers at both ends, it might not be completely safe, but it can be done safe but not to code without separate wire runs. My original thought was to back feed in at the Air Conditioner where I have a #6 run, straight back to the panel. I know it would be safe, but again, code will not legally allow it.
DIY work should be done to code. And so far, everything I have done is within code. And I stress to anyone else here, look up the codes and plan it all to meet code or exceed it. I typically go one wire gauge larger than code requires. Electrical fires are bad news. No one wants to see that happen. Same thing with any shock hazard, do you best to make it as safe as the code if not better. If you do have anything wired odd, make a note of it and leave it in the panel or box where it was done. I used to have dimmed outputs for lamps. ALWAYS label anything like that.
The one thing I keep finding in my own home is bad neutral branching. I just installed a new WiFi dimmer. The single red wire nut was holding 5 neutral wires in the back of the box. OUCH! This does meet code, but it sure makes it hard to work on. The WiFi dimmer needed a neutral feed. I found the neutral wires going out to the lights and split those off. Now the neutral from the main panel splices to an outlet and two #12 wires. On feeds the dimmer neutral terminal, and the other now splices to the light fixture loads. Each wire nut has 4 wires in it now. But the box is totally crammed now.
zanydroid
Solar Wizard
Another rule is that inverters need to be on dedicated branch circuits to rule out the need to calculate whether multiple power sources feeding one circuit can overload some outlets. It is theoretically possible, but if you have no loads then it is mathematically impossible. And NEC seems to want very very idiot proof level of safety here.
European electrical code allows backfeed into a branch circuit under a certain (low) inverter power level. This would also help with their equivalent of 120% rule since power levels that small are likely well within the safety margin of the consumer units on the path to the service drop.
GXMnow
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The way things are going, it is almost cheaper now to get a small AiO solar inverter instead of a UPS. Many of them even have the transfer switch built in now. They are true (Off Grid) units and can't back feed the grid. As long as th solar produces enough energy, it will run the output off of the battery that is being charged by the built in MPPT charge controller. But if the battery runs low, it will tie the loads to the grid to keep them running until the battery charges up again. It's a one box solution that just needs batteries connected to it.
zanydroid
Solar Wizard
I am eagerly waiting for UPSes to converge with AIOs. Unfortunately the UPS companies are probably just going to keep cranking out those ancient designs for a really long time until forced to stop.
Maybe AIO companies should start pursuing UPS reliability and transfer times. And get the UPS listing in addition to 1741
Yeah. I live in an area where the utility is somewhat more hostile towards rooftop solar - i understand their reasoning but it doesn't specifically help me lol. Of course that only really matters if I put solar back out onto the grid, which is what I want to avoid. This information is helpful.
Is this not sufficient?
Go to time mark 29:25 for demonstration of "seamless switching" UPS function of the EG4 18KPV.
That seems like it would negate the need for a UPS.
Based on my experience with UPS units, the inverters are already more reliable.
Mike C.
those EG4 18k units seem really nice and simple to install. I wonder if it can be controlled / monitored with either solar assistant or home assistant? i also wonder if you can connected to DC loads so you dont have to run the actual inverter part too.
No experience with it, but there is a guide to connecting Solar Assistant to the EG4 inverters:
In theory, if the 18KPV had a battery attached, you could draw from the battery terminals and the 18KPV would maintain the battery charge level, thus powering your DC loads. I would expect you must have a battery to smooth things out, a directly connected DC load probably does not work given the way a load might mangle to voltage. The 18KPV expects a battery that doesn't change voltage very quickly.
Again, in theory. I have no data or experience to confirm this.
The EG4 18KPV specs list a "battery charge efficiency" of 95%. It wasn't clear if this was PV to battery or grid to battery. I would expect PV to battery to be in that range, however.
Mike C.
Ok. I will have to look into it more I think. it would make sense that you could run DC loads directly from the batteries but only one of EG4's technicians could answer that question. over time I think that more and more appliances will be offered in DC currentNo experience with it, but there is a guide to connecting Solar Assistant to the EG4 inverters:
In theory, if the 18KPV had a battery attached, you could draw from the battery terminals and the 18KPV would maintain the battery charge level, thus powering your DC loads. I would expect you must have a battery to smooth things out, a directly connected DC load probably does not work given the way a load might mangle to voltage. The 18KPV expects a battery that doesn't change voltage very quickly.
Again, in theory. I have no data or experience to confirm this.
The EG4 18KPV specs list a "battery charge efficiency" of 95%. It wasn't clear if this was PV to battery or grid to battery. I would expect PV to battery to be in that range, however.
Mike C.
Electrodude
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Now, I agree that's dangerous.
wpns
Solar Joules are catch and release
EG4 says they don't currently recommend Solar Assistant because they haven't qualified it, so I'm planning on connecting it for monitoring only to begin with.
wpns
Solar Joules are catch and release
Since the EG4 18Kpv can talk directly to the batteries in closed loop mode, it doesn't have to infer the SOC from tiny voltage changes, so there shouldn't be any problems with using 48V power from the battery bank(s) directly. Plus or minus the DC wiring issues, and if you're only drawing a fraction of C, then I can't imagine you'd have any problems.
Ok. that is a shame. would be cool if they allowed that. but monitoring is still good. When i get all the things I want up and running, I would likely try to integrate it with home assistant. I wonder why some companies are more resistant to allowing integration into these services. Makes it easier for them in some ways
yeah. I may shoot over a few questions to the EG4 people to see what I can learn. Since i'm a newbie, I kind of want to build a small system first to get my head around this stuff. I am in the process of doing an efficiency upgrade to my home, so it doesn't make sense to go full solar until I know what changes and until I get a good idea on what my loads are. I have considered doing some basic energy monitoring, but I don't know how much value I would get from that right this moment (or what is the best method for it).
jjww
Stuck in PG&E Land
FYI, Solar assistant reads data off the 18kpv just fine. BUT very minimal control functions are available
(charge /discharge voltages and start/stop voltages for smart load only) and this only showed up in last
solar assistant upgrade.
(charge /discharge voltages and start/stop voltages for smart load only) and this only showed up in last
solar assistant upgrade.
