Safety and Legality of DIY Small 300 Watt Grid Tied Inverter

[russ]

That is not 'guts' - that is stupidity.

[DavidRx]

Why doesn't someone design ...

I'm no expert in electrical or electronics but it would seem to me that it should be possible to desgn a simple grid-tied plug-in panel that would be safe and legally compliant.
?What is keeping that from happening? This is what guerilla solar should be working to create... Turn guerilla solar into solar for the masses, millions of panels plugged into the grid. DIYers and Makers, get to work!

[russ]

It is a modification to the home's electric supply system - if done wrong things can get smoky.

The unit has to be connected to the buss in the panel in a correct manner - not just plugged into a wall socket.

That is unless you are one of those with 27 connections to one plug in.

[DavidRx]

Your answer is trivial and does nothing to respond to my observation/question that we can and should do better. I am a degreed engineer from MIT. I've seen the connection from my first legal micro-inverter grid-tied solar panel installation. It's nothing more than a mechanical switch, several breakers and wiring, + to +, - to - and ground to ground. The reality is that there are large utilities and an antiquated building department structure entrenched in this country that are unable or unwilling to see this sort of thing happen. California utilities were required by law to pay for excess electricity generation several years ago. They dragged their feet and took almost 2 years to implement the payback system for the consumer. In the end they pay only a fraction of the value of the power people like myself put into the grid. They are making money off of my excess power, fortunately I sized my system to minimize the excess. So back to the original observation. The wiring issue is simple as I see it given that a three prong plug has all the correct polarity/wiring built in to it's design. As far as the safety issue of power in the system when there is a power loss, it would seem to me that a device that kills power in a similar manner to a GFI would be able to sense when power from the grid goes down and shuts itself off would work. Let's see some well thought out responses.

It is a modification to the home's electric supply system - if done wrong things can get smoky.

The unit has to be connected to the buss in the panel in a correct manner - not just plugged into a wall socket.

That is unless you are one of those with 27 connections to one plug in.

[Sunking]

?What is keeping that from happening?

The plug with exposed live parts. Think of this way how would you feel if all the receptacles in your home were plugs (male) instead of receptacles (females). Your kids would have a lot of fun learning about electricity and would also keep you local fire department really busy putting out house fires. Codes and Listing requirements forbid it, not to mention Fire Departments and insurance companies.

[DavidRx]

Great! Another rock thrower rather than a problem solver. We have so many of you to send back for reeducation. ONE POSSIBLE ANSWER: A spring loaded cover that prevents the plug from being exposed until it's plugged into the wall. This can't be any worse than the toaster in your kitchen!

The plug with exposed live parts. Think of this way how would you feel if all the receptacles in your home were plugs (male) instead of receptacles (females). Your kids would have a lot of fun learning about electricity and would also keep you local fire department really busy putting out house fires.

[inetdog]

So back to the original observation. The wiring issue is simple as I see it given that a three prong plug has all the correct polarity/wiring built in to it's design. As far as the safety issue of power in the system when there is a power loss, it would seem to me that a device that kills power in a similar manner to a GFI would be able to sense when power from the grid goes down and shuts itself off would work. Let's see some well thought out responses.

Thinking well.... pause.... still thinking.....responding:

1. For a DIY setup, this assumes that either you trust that all 3-wire outlets are properly wired, (Check with any home inspector for statistics on this one.) Or that the device incorporates an outlet tester which works before it energizes, or even connects any other internal parts to the outlet wires.
2. Without hard wiring, there is no simple way to create a pluggable connection which is safe regardless of which side it is powered from. Yes, there are connectors which are shielded in both directions, but not that match a standard outlet.
3. Yes, the output cord is not energized unless the device is operating. Are you willing to depend on that?
4. Anti-islanding is a complex problem about which a lot of design work has been done. The upshot is that almost any simple detector will have a region of load, etc. for which it can fail when the grid power goes out. And the grid can fail in more ways than just becoming disconnected. A simple GFCI design works because all it has to do is detect when the current in two isolated wires is equal or unequal. In a grid-tie, the power can be going in either direction at the main disconnect, and the problem is to detect whether the voltage on the inverter output is coming from the grid or from a not-necessarily resistive load which is accepting the inverter output. Disconnecting the inverter at frequent intervals to test is not practical, since it would either allow a fault to continue too long or interfere with normal operation. There are some good solutions for anti-islanding, but not necesssarily for the situation in which the interconnect is pluggable.
5. Should I trust that a product, which is explicitly designed and marketed to be used in violation of applicable regulations, has been safely designed? Reasonable people may differ on this.

[billvon]

So, these are obviously coming from Asia and it seems that even sellers in the United States do not list these items with proper English. But, if you search completed listings on Ebay, there's a lot of these selling. So, it seems people are buying them and I assume they're using them in the U.S.

Oh, definitely. I've tried them and they do work, in that they put power back on the grid. And some (like the Trace Microsine or the Enphase inverters) are indeed designed to be safely used with lower power circuits. If you used one of those inverters you'd be fairly assured that they meet basic anti-islanding requirements.

But if you get an inverter that does not meet those requirements you could easily island loads, and that presents a hazard to both you and people working on your utility lines. You could test them to make sure they won't island, but to do that competently requires more test hardware than most people have.

[billvon]

I'm no expert in electrical or electronics but it would seem to me that it should be possible to desgn a simple grid-tied plug-in panel that would be safe and legally compliant.
?What is keeping that from happening?

Nothing at all. Like I mentioned, the Enphase inverters are designed to do just that, and it would be trivial to put the correct plug and outlet on a dedicated circuit. (has to be 240V though.) If you can find any older Trace Microsines they were designed to do the same thing at 120 volts. But the inverter just one part of a safe system design.

One of the things that worries me is that a safe solar design involves a lot of things - safe and secure roof mounts, good grounding, sunlight compatible wiring/conduits etc. It is unlikely that someone who thinks "it's too hard to run a dedicated line so I just want to use an outlet" will be willing to do the work to wire, anchor and ground an array safely. That's not to say it can't be done, of course; using an outlet to connect a solar power system in and of itself is not unsafe with a good inverter employing anti-islanding protection.

But if Home Depot offered a "just plug this panel in to your kitchen outlet!" home power system you'd see a lot of ugly (and dangerous) installations. I think that's one of the primary reasons no "real" supplier is offering such a system.

[Sunking]

Great! Another rock thrower rather than a problem solver. We have so many of you to send back for reeducation. ONE POSSIBLE ANSWER: A spring loaded cover that prevents the plug from being exposed until it's plugged into the wall. This can't be any worse than the toaster in your kitchen!

Read my lips. It will never happen, code and listing agencies will never allow it. All GTI systems have to be hard wired in and inaccessible. I am one of those coder makers that will never allow it to happen. So get a grip of reality. I am one of the SOB's that brought you AFCI in all new installations and child proof receptacles.

[KRenn]

That is not 'guts' - that is stupidity.

This. The first time some utility worker ends up getting zapped because some moron decided to go around the set regulations and existing rules, all hell will rain down upon whoever that individual was and the penalties and new code inspection requirements will be greatly intensified.


There are so many things wrong with this it is unbelievable. If you have issues with the existing code and regulations, get political, draw up some signs and go fight the power, either that or go Kaczynski and move somewhere to an off-grid location where your foolishness is only going to result in harm to yourself.

[russ]

Your answer is trivial and does nothing to respond to my observation/question that we can and should do better. I am a degreed engineer from MIT.

What degree? Claims such as that on the net are trivial and meaningless.

Any engineer should understand the emphasis placed on safety - especially in a residential/DIY setting.

Your green spiel is cute but it is the standard ''Some bad guys are keeping us from saving the world for their own interests''. That is pure and blatant BS.

Progress is being made - if not fast enough for the green front.

[billvon]

ONE POSSIBLE ANSWER: A spring loaded cover that prevents the plug from being exposed until it's plugged into the wall. This can't be any worse than the toaster in your kitchen!

There are plenty of dead-front connector systems out there; that's actually the least critical part of the problem. Islanding is a much bigger problem (and results in problems that are much different than those caused by a toaster.)

[natel]

what about this

So, here's a seller on Amazon that claims this system is UL certified and that you can get a 30% federal tax credit. Could there be any truth to this?

http://www.amazon.com/Readymade-Inverter-Prewired-Configured-Yourself/dp/B006R7K8MA

[peakbagger]

Unfortunately not. The seller is misrepresenting a product and I expect that their business strategy is to sell the product to unsuspecting suckers and if anyone starts asking questions, they shut down one website and open up another. As for the tax credit aspect, anyone can (and occasionally does) claim a tax credit. It usually takes a couple of years for the IRS to catch up with it and the seller will be long gone before the IRS makes a final determination. Ultimately the tax payer is the one that gets to pay the backtaxes.

There just isnt a way to get around the electrical code when it comes to connecting to the grid. Now if you want to set up a micro grid and not connect to a utility, you can do anything you want in areas that dont require inspections but be aware that if someone gets hurt, its just another reason why an insurance company doesnt have to pay.