Small Grid-Tied Inverter Ideas

[SolarHead]

check this out. small grid-tie inverters, you plug them into a receptacle in your home. If this would provide 500w all day long while sun in shining, that might be interesting. Seems 2 solar panels is all that's needed, I don't know what happens when the grid is unavailable, does it continue sending power and possibly back to the grid (which is illegal and dangerous)? I'd think anyone with a small home, no solar, they could get 2 panels, one of these, very cheap and lower their power bill by quite a bit. Anyone have experience or comments about something like this? Even if you have a big solar system, what if you had one of these completely separated from your solar system, and this thing just supplemented your homes power needs by 500W most of the day? They don't seem to be UL listed so that's a thought.

500W Solar Grid Tie Inverter, 12V/24V DC to 110V/230V AC

www.inverter.com

 

[sunshine_eggo]

check this out. small grid-tie inverters, you plug them into a receptacle in your home. If this would provide 500w all day long while sun in shining, that might be interesting. Seems 2 solar panels is all that's needed, I don't know what happens when the grid is unavailable, does it continue sending power and possibly back to the grid (which is illegal and dangerous)? I'd think anyone with a small home, no solar, they could get 2 panels, one of these, very cheap and lower their power bill by quite a bit. Anyone have experience or comments about something like this? Even if you have a big solar system, what if you had one of these completely separated from your solar system, and this thing just supplemented your homes power needs by 500W most of the day? They don't seem to be UL listed so that's a thought.

500W Solar Grid Tie Inverter, 12V/24V DC to 110V/230V AC

www.inverter.com

I have 1000W and 350W versions.

No, they do not keep sending power if grid down.

Even with that feature intact, they are not legal in the vast majority (if not all) cases (no UL).

The instant the system tries to feed power back to the grid, you risk a knock on the door by the power police, so you'd have to ensure that you NEVER produce more than you use. While we use quite a bit of energy, particularly during the summer, there have been times when I got close with only 350W going back to the grid.

I use these units for a very specific purpose, and they are actually powered by batteries, not solar panels. This limits their output significantly as ~14-15V does not get them into their MPPT range, so the two combined rarely put out more than about 500W. They are never used unsupervised and they rarely run for more than 30-60 minutes at a time.

 

[DThames]

This similar product has a current sensor and regulates output so to not feed back more than you are using. As previously stated, these are not good ideas for several reasons. Still some will elect to use them for testing, training, and other educational value.

 

[SolarHead]

They must just be cheap, poorly made, and borderline dangerous.

 

[DThames]

They must just be cheap, poorly made, and borderline dangerous.

Maybe, or maybe not. It cost money to have UL sold products. Small time MFGs don't have the money nor market to warrant the cost. Home owners insurance, local fire code, building code, etc can all be issues even with a reasonable product that is not UL.

 

[Durk_2007]

The Big problem I see is it could allow more amps on a circuit than it should have. Potentially 4.1A+ 20A breaker = 24.1A not good on wiring!

 

[packetloss]

To be honest, the best and cheapest way to do something like this is to pick up used panels and used micro inverters. Then just add a dual pole 20 amp breaker and wire in the micro inverters. This way you aren't feeding DC into your house at all. It's essentially AC right from the inverter at each panel and it's a lot safer and will be up to code assuming that matters to you.

I had looked at the cheap string inverters and they aren't much cheaper (if at all) than going with used micro inverters. Micro inverters are much easier to install and far less likely to blow and cause a fire or other issues.

 

[SolarHead]

To be honest, the best and cheapest way to do something like this is to pick up used panels and used micro inverters. Then just add a dual pole 20 amp breaker and wire in the micro inverters. This way you aren't feeding DC into your house at all. It's essentially AC right from the inverter at each panel and it's a lot safer and will be up to code assuming that matters to you.

I had looked at the cheap string inverters and they aren't much cheaper (if at all) than going with used micro inverters. Micro inverters are much easier to install and far less likely to blow and cause a fire or other issues.

that sounds like good advice, would have to look at the price tag of microinverters. I have never looked to see how they are priced.

If sending AC to your main panel at the home, you need a device to turn the system OFF if the grid goes down, correct? Otherwise you'll be sending power to the grid when its down, which as we all know is superbad.

 

[peakbagger]

Not sure if anyone pointed it out that these are not legal used in the manner described for grid tie by the OP in the US. The UL 1741 SA standard is required in the US and that put in the place the protections required to keep the unit from backfeeding the gird when the grid is down.

 

[sunshine_eggo]

Not sure if anyone pointed it out that these are not legal used in the manner described for grid tie by the OP in the US. The UL 1741 SA standard is required in the US and that put in the place the protections required to keep the unit from backfeeding the gird when the grid is down.

Posts 2 and 3

 

[packetloss]

that sounds like good advice, would have to look at the price tag of microinverters. I have never looked to see how they are priced.

If sending AC to your main panel at the home, you need a device to turn the system OFF if the grid goes down, correct? Otherwise you'll be sending power to the grid when its down, which as we all know is superbad.

Micro inverters (at least Enphase) are grid tied. They only send if they detect voltage on the line (i.e. the grid is up). Not an expert on this but I don't believe you need a "rapid" shutdown device as it's AC lines on the roof and entering the house and not DC. With a string inverter you have DC on the roof and entering your house till it's converted to AC by the inverter. With a micro inverter it's converted to AC right at each panel.

 

[ncsolarelectric]

In the US, if you want a grid-tied inverter that can send power back to the grid, you need a NEM agreement with your local utility. The NEC regulates how you can connect the inverter to your home, but it's not complicated or difficult. Depending on where you live, the interconnection agreement and permit are not complicated or difficult. Unless you live in a major city/county area, it's pretty easy to go grid-tied. The Hoymiles HM-1500NT microinverters are UL listed but require 4 solar panels and a circuit breaker to connect to your main panel. That's all.