New to forum & Enphase M190 Inverter questions

[TxMike]

Hey guys,

I asked this question on another forum and didn't really get any answers. I was hoping you guys could help. I have come into a situation that I could use some advice on. I acquired a number of minor damaged solar panels cheap and I would like to install some at my father's place to help offset his utility bills. Just a small trailer out in the country. The "traditional" method of installing these is to run them together in series into an inverter and then into a disconnect and then into the mains on a breaker if I am reading all the installation notes correctly. A good DC-AC inverter is pretty pricey and I am not wild about having the old man working around high voltage DC power.

I have an opportunity to acquire some Enphase M190 micro-inverters that do the DC-AC conversion at the solar panel allowing you to run AC to the mains. It is supposed to be a more efficient setup and has a few other benefits. The issue is the Enphase inverters are 208v, 3 ph meant for industrial installations. I know it is possible to take the 208v to an appropriate transformer and get 120 out of the secondary side. Since these inverters are grid tie, they utilize a sensing circuit to recognize the correct incoming line voltage and this allows them to operate, as they are designed to shut off in the event of a power failure thereby protecting anyone working on the line upstream. My question is twofold: One, will these units work if attached to a transformer rather than directly to the grid and second, are there any safety issues that might arise if they do indeed work. My initial thinking is "No" to the first question and "Yes" to the second, but I would like y'all's professional opinion. Lastly, if it is possible to make these inverters work safely and efficiently, what would be the best way to construct the circuit?

[sdold]

Do a search on the M190, they had high failure rates. I like Enphase inverters, but I'd avoid those.

[TxMike]

Do a search on the M190, they had high failure rates. I like Enphase inverters, but I'd avoid those.

I agree with that assessment. However, for the cost of these 190's, I can replace them 3 times before I reach the cost of one of the newer versions. Also, I have read of reliability issues with just about every micro-inverter out there. So, it seems I take a gamble no matter what and the 190's do have a 15 year warranty. I hear Enphase can be slow to replace them but I am planning on buying a few spares anyway. I just need to know if these will work for my application first. Thanks for the reply.

[sdold]

The reports of M190 failures dwarf those of the M215 and M250, according to what I've read from owners and installers.

[sensij]

You wouldn't just want to convert to 120 V, you would need to convert to 240 V. I think with the money you spend on the transformer, you could just buy 240 V microinverters. If you really want to take your chances with the M190 instead of a newer generation, you can get them for ~$100 ea on Ebay. The newer ones aren't that much more.

I hope you understand that it isn't legal to just start hooking these up... you'll need approval from your power company, and that in turn usually requires a permit and inspection from your city or AHJ.

[TxMike]

You wouldn't just want to convert to 120 V, you would need to convert to 240 V. I think with the money you spend on the transformer, you could just buy 240 V microinverters. If you really want to take your chances with the M190 instead of a newer generation, you can get them for ~$100 ea on Ebay. The newer ones aren't that much more.

I hope you understand that it isn't legal to just start hooking these up... you'll need approval from your power company, and that in turn usually requires a permit and inspection from your city or AHJ.

Actually, the price on the 190's has fallen much more (I assume due to the known reliability issues) to the $35 -$40 ea. range, hence the 3x replacement comment. My main concern with these inverters I am looking at is the fact the are 3 phase and can not be tied directly to the single phase grid. I just really need to know if there is a sensible work around so these can work out. If not, I will go the traditional route and run a DC string to a grid inverter and carry on from there.

It goes w/o saying that all legal precautions will be addressed, hence the reason for my posting the inquiry on this board. Otherwise, I would have just ordered a few of the inverters and fiddled around with them until I either fried the inverter, the house, someone upline on the grid, or myself........I would much rather do it safely, legally and correctly. I am posing the questions here first as I am not too excited about paying an electrician $500 just to show up to my house and say "Nope, Ain't gonna work". If I find out here that the project is feasible, THEN I will go through the expense of bringing in professional help.

[inetdog]

I have an opportunity to acquire some Enphase M190 micro-inverters that do the DC-AC conversion at the solar panel allowing you to run AC to the mains. It is supposed to be a more efficient setup and has a few other benefits. The issue is the Enphase inverters are 208v, 3 ph meant for industrial installations. I know it is possible to take the 208v to an appropriate transformer and get 120 out of the secondary side. Since these inverters are grid tie, they utilize a sensing circuit to recognize the correct incoming line voltage and this allows them to operate, as they are designed to shut off in the event of a power failure thereby protecting anyone working on the line upstream. My question is twofold: One, will these units work if attached to a transformer rather than directly to the grid and second, are there any safety issues that might arise if they do indeed work. My initial thinking is "No" to the first question and "Yes" to the second, but I would like y'all's professional opinion. Lastly, if it is possible to make these inverters work safely and efficiently, what would be the best way to construct the circuit?

1. The units will work just fine attached to the right transformer rather than directly to the grid. The right way to do it, as noted by another member, is with a 208 to 240 transformer, not 208 to 120.

2. There are no safety issues provided that the transformer is installed properly, with overcurrent protection, grounding, and bonding compliant with the NEC. DIY is not a great idea, but an electrician who is not familiar with solar should still be able to install the transformer.

3. It is possible for it to be economical, if there is no requirement for an electrical permit and inspection. The cost of the latter may make it uneconomical for you.
It will also likely be safe and efficient if there is a permit and inspection. On the other hand if there will be no permit and inspection, I am not going to give you any advice on how to wire it, since my liability would be too great.

[sensij]

I think you may be misunderstanding. There are two versions of the M190 (and their other microinverters). One version for three phase, another version for 240 v single phase. Even if the 240 v version costs a bit more, it is probably worth getting, so you don't have to buy and install transformers.

[TxMike]

1. The units will work just fine attached to the right transformer rather than directly to the grid. The right way to do it, as noted by another member, is with a 208 to 240 transformer, not 208 to 120.

2. There are no safety issues provided that the transformer is installed properly, with overcurrent protection, grounding, and bonding compliant with the NEC. DIY is not a great idea, but an electrician who is not familiar with solar should still be able to install the transformer.

3. It is possible for it to be economical, if there is no requirement for an electrical permit and inspection. The cost of the latter may make it uneconomical for you.
It will also likely be safe and efficient if there is a permit and inspection. On the other hand if there will be no permit and inspection, I am not going to give you any advice on how to wire it, since my liability would be too great.

Let me reiterate that my whole reason for even looking at this project is that I am trying to provide solar power for my Dad's place in an economical and SAFE way. The only reason I am entertaining the idea of these AC micro-inverters is that they don't have 500 - 600 volts of DC power going through them. I can just see my 82 yr old Dad getting curious about the whole setup and start tinkering around it. I just know how he is. A grounded AC system with only a few amps is going to be much safer for him that a standard inverter with high voltage DC. I know each of the hots on the 208v provide 120v to the transformer taps and that's not really my issue. The main issue is that Line Voltage sensing circuit that looks for grid power before it will allow the inverter to operate. I am not sure how it can sense incoming grid power back through the transformer unless I am just missing something. If there IS a way for this to operate, then that's great. I just want to confirm (with an explanation for my own understanding) that this will work before I go out and purchase these inverters only to find they will not operate correctly given the transformer setup. Any actual electrical connections (inverters to the transformer and transformer to mains panel) will be done by a qualified electrician for safety and insurance purposes.

[TxMike]

I think you may be misunderstanding. There are two versions of the M190 (and their other microinverters). One version for three phase, another version for 240 v single phase. Even if the 240 v version costs a bit more, it is probably worth getting, so you don't have to buy and install transformers.

Yes, I do understand that there are the different versions, however the older M190's in single phase 240 are almost as expensive as the newer M250's for some reason. I am only considering these 208v 3 phase M190's as they are very inexpensive due to the fact they are not just plug and play in a standard single phase residential application. I wish I could afford to supply my Dad with all new top-of-the-line equipment professionally installed and monitored but I'm just not a wealthy guy. I have to settle for used equipment cobbled together and try to make the best of it. That being said, I will gladly pay for the electrician to do the actual tie ins but the rest of the install is on me.

[paul65k]

Yes, I do understand that there are the different versions, however the older M190's in single phase 240 are almost as expensive as the newer M250's for some reason. I am only considering these 208v 3 phase M190's as they are very inexpensive due to the fact they are not just plug and play in a standard single phase residential application. I wish I could afford to supply my Dad with all new top-of-the-line equipment professionally installed and monitored but I'm just not a wealthy guy. I have to settle for used equipment cobbled together and try to make the best of it. That being said, I will gladly pay for the electrician to do the actual tie ins but the rest of the install is on me.

Interesting....my 190's are capable of 3 phase but will also (and does) work in my single phase residential environment. The documentation on mine simply says to not hook up the extra wire (orange from memory??). I'm not disputing that the ones you are looking at only work in 3 phase but I'm surprised as the "Standard" ones that I have will also work in a 3 phase environment.

So.........I either have the 3 phase inverters which will obviously work in a single phase installation or I have the single phase inverters that will also work in a 3 phase environment. I recommend that you get the specific part numbers of the inverters you are looking at then go to the enphase website, download the installation instructions and I'm guessing everything you want to know will be right there....good luck and don't let the naysayers turn you away from the 190s........in your case as a self maintainer you should be fine, just make sure you monitor your envoy and deal with issues as they come up.

[TxMike]

Interesting....my 190's are capable of 3 phase but will also (and does) work in my single phase residential environment. The documentation on mine simply says to not hook up the extra wire (orange from memory??). I'm not disputing that the ones you are looking at only work in 3 phase but I'm surprised as the "Standard" ones that I have will also work in a 3 phase environment.

So.........I either have the 3 phase inverters which will obviously work in a single phase installation or I have the single phase inverters that will also work in a 3 phase environment. I recommend that you get the specific part numbers of the inverters you are looking at then go to the enphase website, download the installation instructions and I'm guessing everything you want to know will be right there....good luck and don't let the naysayers turn you away from the 190s........in your case as a self maintainer you should be fine, just make sure you monitor your envoy and deal with issues as they come up.

The actual part number of the ones I am considering are M190-72-208-S12. I have been studying the Enphase website, which is where I confirmed these were 208v, 3 Ph inverters. I did not see anywhere in the installation manual where it confirmed or denied the ability of those inverters to work in a single phase environment. I would really like to know the exact model number of the ones you have installed. If I can get away from having to use a transformer, then of course, my install cost goes way down and I only need to pay an electrician to do the main panel connection. If you would be so kind as to take a peek at the model number of your inverters, I would truly appreciate it. Thank you for your post!

[inetdog]

The actual part number of the ones I am considering are M190-72-208-S12. I have been studying the Enphase website, which is where I confirmed these were 208v, 3 Ph inverters. I did not see anywhere in the installation manual where it confirmed or denied the ability of those inverters to work in a single phase environment. I would really like to know the exact model number of the ones you have installed. If I can get away from having to use a transformer, then of course, my install cost goes way down and I only need to pay an electrician to do the main panel connection. If you would be so kind as to take a peek at the model number of your inverters, I would truly appreciate it. Thank you for your post!

The problem is not the single versus three phase configuration. It is that 240V is above the upper limit of grid voltage for the 208V model.
Later Enphase micros use the same hardware with at most a change of a configuration setting to handle both nominal voltage options. The 190 had two hardware options because the voltage range capability of the unit is too narrow.

[TxMike]

The problem is not the single versus three phase configuration. It is that 240V is above the upper limit of grid voltage for the 208V model.
Later Enphase micros use the same hardware with at most a change of a configuration setting to handle both nominal voltage options. The 190 had two hardware options because the voltage range capability of the unit is too narrow.

Ok, I can see that now. Whereas the 240v model's lower limit is 211v, the 208v model's upper limit is 229v. So, it's back to a step up transformer. This brings me back to my original question of whether the inverter will function correctly by sensing the incoming line voltage using a transformer between it and the grid? I know how a transformer works but I don't understand how the inverter can sense the line voltage through the transformer.

[sensij]

Interesting....my 190's are capable of 3 phase but will also (and does) work in my single phase residential environment. The documentation on mine simply says to not hook up the extra wire (orange from memory??). I'm not disputing that the ones you are looking at only work in 3 phase but I'm surprised as the "Standard" ones that I have will also work in a 3 phase environment.

In this post you said you have M215's, which are able to be used on either 240 V single phase or 208 V three phase systems, as Inetdog explained. Your experience doesn't really help the OP here.

To the OP: Another consideration is that with the 3 phase model, if you want to monitor the panel output using the Enphase Envoy, you'll need a phase coupler (Enphase LPC-01), which appears to cost a couple hundred with limited vendor options. The powerline communication used by Enphase will not survive a trip through the transformer. Given that the solar panels you've picked up are "minor damaged", you should probably consider some kind of monitoring to watch what they are doing. Although it is rare, a damaged panel can develop a hot spot and become a fire hazard.