Grid Tie Inverter for lower voltage arrays

[Atokatim]

I am finally moving to grid tie my solar panel setup and will have to get everything inspected before making the connection.  In order to pass, I need a decent inverter for my current setup but would like room to add more panels in the future.  Currently, I have 4 120W panels that have a max voltage of 21.5.  Most good inverters have an operating range of 150V to 450V which I cannot reach with 1 array.  Even if I added 4 more panels, the most I could produce would be 172V in full sunlight....just enough to kick on the inverter.  So, I will need something with a much lower operating range.  I can work with a 110V AC inverter if that is the way I need to go.  Any recommendations?  My budget is less than $500.  Stackable is ok as well.  As long as it passes the final inspection.

[dnix71]

Where do you live? Most places have a list of approved equipment. Your electrical power supplier is the one to ask. $500 is not a real number for a UL/UN/CSA listed grid-tie inverter. Enphase inverters are in that price range, but they may require a controller that costs more than that. Enphase inverters go on each panel and can be stacked, so they do not require high voltage.

[Atokatim]

I live about 1 hour north of Memphis TN.  I am working with a solar installer to get this finished and he has dealt with the state inspector and know what he likes to see.  The inverter is not a huge deal, as long as it turns off AC output when the grid is disconnected from it.

[Mary B]

Not knowing your budget... Outback has lower voltage grid tie inverters https://www.solarblvd.com/product_info.php?cPath=7_70_124&products_id=697

[dnix71]

Mary B He said $500. Not a real number for an legal/safe grid-tie inverter. The Outback is almost 4 times that. The Outback would certainly meet standards, though.

[Atokatim]

So there is no such thing as a 500W Grid tie inverter for $500 that can be passed with a state inspection?

[dnix71]

http://www.solar-electric.com/abb-micro-300-watt-grid-tie-inverter.html?gclid=CO_wyKqAwMUCFdcXHwod-J0Arw
This one meets legal requirements, but as with Enphase, you need one per panel. In the long run that is expensive. The best use of micro inverters is if you have shading problems, or a mixed batch of panels. The inverter listed above also requires a special connector to prevent hooking them up backwards. MC4's are symmetric, it is possible to wire them both ways. The new connector is an Amphenol H4.

http://www.solar-electric.com/inverters-controllers-accessories/gridtiesolar/enmigrsy.html  Enphase units listed here.

You haven't said why you want to grid-tie. A couple hundred watts of panels won't run much and won't pay for itself anytime soon unless you get some government incentives to buy the panels or sell back the power. For any grid-tie install you will need a different electrical meter and an enclosure that acts as an interface and disconnect with the utility supply.

http://www.solar-electric.com/inverters-controllers-accessories/gridtiesolar/sma-sunnyboy-grid-tie-inverters/sma-microinverters-and-accessories.html  SunnyBoy listed here. The controller plus one micro inverter is almost within the $500 range.

Are the panels going to be on the ground on mounts, or on the roof?

[Atokatim]

Right now, Grid tie seems to be a better option for me since with a couple more panels, I can reach the 500W minimum required to meet the TVA buy back program regulations.  They pay a little over the going rate per kWh for solar and 500W would be great since my base line average on my house is around 300W per hour. 

I have designed a stand along power logger that detects the IR pulse from my meter which is equal to 1 watt hour.  It counts the time between pulses and displays the current power usage in watts and WH on a display next to my computer.  It also uploads the data to my server for viewing and calculating power usage after changes.  It is accurate within $2 to $3 of my actual bill.

The panels are ground mounted on a single schedule 80 4" pipe and can follow the sun from the time it comes up, till the time it goes down with a 3 degree accuracy.  This is also another circuit I built which can be controlled to "park" the panels in high winds or be control via my phone from anywhere.  This has been in service for over 1 year with no major malfunctions.

The solar panels are charging 2ea 115Ah deep cycle batteries that run my 12/24V LED T8 lights in my shed and my home made motion activated light switch.  The lights draw roughly 8A and the motion switch draws 1mA when off and 200mA when on.  I am wasting generated electricity floating my batteries all day long since I am only in my shed for a max of 1 to 2 hours every other day.  Using all the generated power from my panels would seem like a more feasible reason to have spent so much on these solar panels.

[dnix71]

I lived in Chattanooga for a year on Cameron Hill overlooking the Tennesse River and downtown. At 5pm Chattanooga rolled up the mat and people went home to Dayton or Soddy-Daisy. The apt complex burned down sometime after I left. My electric bill was $10 a month in a split-level flat. TVA charged something like 4 cents a KWH and almost no base account fee. Those were the days.

You will cut your bill with 500 watts [nameplate] of panel. Some power companies are not very nice about paying for grid-tie. The TVA seems to be one that really doesn't mind paying. Is Racoon Mountain pumped storage still in operation? I heard it leaked.

I worked for the TVA for a year in water quality. They had not opened Sequoyah nuke at the time. Watts Bar was still coal fired. Belafonte was next in line and Phipps Bend was moth-balled in plastic.

[Atokatim]

Not sure about Raccoon mountain.  Never heard of it

So, all these 500W Ebay Grid tie inverters are jokes even with excellent reviews on Amazon as well?  I am wiring for a proper grid tie installation including disconnects, ground rods, wire sizes, conduit, etc.  I am at the stage now to get the inverter and am lost on what to get.  I don't need a 3000W inverter and I am sure I can power a 300W inverter with ease.  A 500W is minimum to go with the TVA buyback program so that is what I am on the hunt for.  If I want to expand in the future, buy another inverter to run in line with the other....

[dnix71]

The eBay inverters that plug into the wall are illegal in the US because the NEC requires them to be hard-wired to a proper disconnect/breaker. I suppose you could put one in an enclosure to meet that requirement, but I don't have any faith that cheap junk like that would actually work properly. I don't think you will find any proper certs (UL/UN) on those inverters, either. If you see something with a "CE" label it means it has no real cert, it was self-certified by the manufacturer.
http://www.ebay.com/itm/Swea-Solar-Grid-Tie-Inverter-System-250-watt-CE-listed-/261751577008 This is an example of an inverter that is not legal in the US.

http://www.ebay.com/itm/1000W-Grid-tie-inverter-Pure-sine-wave-inverter-110V-or-220VAC-Solar-Inverter-/141462386334
This one plugs in the wall. That isn't legal and it has no proper certs.

[Atokatim]

Ok, that is kind of what i figured, but was not expecting to pay over $1 per converted watt for a half way decent inverter.  Most inverters I have found that are UL listed are HUGE and I don't have enough panels to turn on or efficiently use one of these inverters.

I have also run into another issue with the state....  According to the state inspector, I have to have an engineered drawing of my solar panel setup which I don't have.  I am guessing I have to higher an electrical engineer to come out and draw up the plans for the installation for around $2000.  Solar seems to be quite expensive mostly due to codes.....

[Bruce S]

The expense comes from the engineers and going grid-tie.
The codes is what helps first responders be aware of what you have.
State to Sate, I have not seen anything they cross-share, but they are getting close.
Most of the first responders are the driving force behind this and quite a few I've had the pleasure of hearing speak have one of 3 types.
1)Grid Tie
2) Off-grid
3) Hybrid (Grid-tie with battery backup)
Fire Fighters need to know when they get to a building if there ax is going to explode when they bunch through a smoldering cable.

[Atokatim]

So at my point, I should stay right where I am running just my lights?  What about not going Grid Tie and go Off Grid on a few things like TV, Lights, and computers?  Leave the big items like AC, Fridge, and oven still tied to the grid?  I know I would have to install a new panel in my house, but I could switch over those specific circuits to the new panel and just have to maintain the batteries and inverter.  I am sure I would have to get an electrical engineer involved with this as well?

[dnix71]

I use the grid as a battery bank. Every thing that I can is 12v direct. What isn't practical to go 12v is still on the grid. The irrigation pump is 1 1/2 HP and on grid. My washing machine was special ordered through Walmart. It's apartment sized and portable, but still does full loads. It uses 1/8 KWH per full regular load. It's on grid, but can be run from an inverter in my van if the power goes out and there is still water. My room light and 12v fan and fridge run from the batteries. The 2 bathroom lights are 1.1 watt LED. Both light the bathroom fully and are on grid. I have battery powered shed lights in the main room and bathroom for when the power goes out. Cooking is nat gas piped in. I have a/c but don't use it. I was born in Florida, and I'm willing to trade comfort for money.

My alarm clock is 12v direct. No parasitic loads. Those really add up. Unplug everything you aren't actually using and you will see the difference.

My electric bill has been less than $10 a month for the last 2 years.

My computer is a laptop and I use a battery powered wireless hotspot for internet. Both run from the grid at work and at home, unless I'm at home during the day and there is extra power.

The power company probably knows what I'm doing but I don't mess with their stuff. No guerilla grid-tie. I have about 800 watts of panel on the ground and propped up on a utility trailer that has a proper road license plate. 2 off grid MPPT's feed 4 12v deep cycle batteries.

[Atokatim]

I am not sure my wife and kids would be willing to give up the AC or the oven   I would not mind, but I don't get to make that call....lol.  I have also been tinkering with ammonia refrigeration like the crosley icyball and the Einstein fridge but that is a whole other project.

So for recommendations....

Going Grid Tie - Looks like it will cost thousands for a simple 500W system due to code / regulation requirements.  Will have to comply with NEC and will need an electrical engineer to design the installation for each component I have bought already and need to buy.

Going Off Grid with some items - Will probably have to get this inspected and will still need a $2000 inverter.  Will have to comply with NEC and will probably still need an electrical engineer.

Going Off Grid with some items converting to 12V DC - Should not need an inspection but will have to run hundreds of feet of thick wire back into my house to convert some items to 12V.  This will cost quite a bit since I have to buy new items that can work from 12V.  The voltage drop of that kind of distance would be pretty bad.

[OperaHouse]

Power wise it would be easy to run a fridge during the day with minimal battery.  I do that now but I have complete control of turning it on and off.  A micro would have to monitor the battery condition and whether the fridge was running or not.  A fridge runs for about 15  minutes and it would be easy to determine you had enough power for that. you can switch back to grid power any time the fridge is not running.  The same thing could be done with a set of outlets in a room.  Just switch back and fourth between grid power and battery.  I require a full battery before switching on inverter.

[Bruce S]

The grid-tie route is still a viable option, BUT check to see if your State/local/Grid have incentives for going that route. Some do, for those Federal mandated reasons.

Depending on where your panels and batteries are located, you could do what other have done very successfully (including a neighbor of mine) instead of running welder's gauge wire from panels to batteries or batteries to house for inverter; locate inverter near batteries (best idea in most situations ) run 120Vac wire to house, using specifically color coded outlets (Mine are orange) for use during the times there is extra power.

Could be anything , beer chiller    , etc

[Atokatim]

If I were to run an additional 110 into my house, would that not require the state to come inspect that?  As said in a previous post about the fire department cutting into something and thinking the power was off.....  that would probably void my home owners insurance.

[Mary B]

As far as an engineering drawing all they want is to see all the components laid out along with a wiring diagram of how it all connects to make sure it has the proper disconnect, proper size wires, UL rated components... Each part should be labeled with that label going to a parts list with part numbers and manufacturer etc. Not hard to do just draw it all out.