10.78kW Enphase system and XW6048

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  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048
    jaggedben wrote: »
    er...Maybe I'm not understanding what you're thinking, but I have a bunch of questions. For example, I wouldn't put that SSR on a roof. Nor could it be spliced into the Engage cable.
    This is not my area of expertise, I am going by the datasheet that lists 100C as the max ambient working temperature and deliberately oversizing the components for longevity. I am currently waiting for their pre-sales Engineer to get back to me. Probably Monday at this point. I'm still looking at what might work. If I can find a reasonable cost SSR for the DC side, that would make it easier. The AC side SSR cost $14 each. The DC side to handle the current cost $75-$95 each. And getting into the new enphase engage cable may be troublesome so I would like to work on the DC side.
    Note also that the Enphases have a 5 minute wait time after grid power is applied. That's just another reason why I think attempting to turn them on and off individually is kind of quixotic; you're not going to be able to respond immediately to all kinds of loads. I still think you really should be thinking about configuring appropriately sized groups of the Enphases to 'bulk' loads that can start slowly and stay on for a while. Those loads would begin with battery charging and then perhaps go on to include other stuff you might have, such as a well pump or water heater (aka 'dump loads').
    The batteries will be large enough to handle the loads until the enphase micros come on line and charge the battery plus maintain the loads. Turning off the micros off quickly is important. I want to turn them off to prevent the XW/SI from frequency shifting and dropping them all at the same time.

    It may be that I end up at having to do strings of micros and match to the running loads. There are always options, it just depends on how much sweat equity or cash you are willing to spend. Currently I have more of the former available!!
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    10.736kW Enphase system with 11 "strings"

    I finally got everything signed and the project is almost done. I got distracted by other projects and forgot to update this one. I did get the Leaf and had a 240volt EVSE installed before the PV project was even approved by SRP. I also installed a Brultech Home Energy monitoring system.

    I chose SunRenu, a local company, to install my system. They were not the cheapest. They were willing to install what I wanted, an Enphase system with 44 panels. After the discussions here, I decided to have them installed with 4 panels/inverters to a string, with 11 strings coming together in an AC combiner panel in the garage. That goes back outside to the required solar meter, a disconnect and into the new 400amp Service Entrance (SES) backing feeding through a 50amp breaker. The SES has a new 250amp main breaker that SRP required. SRP also replaced the 3/0 aluminum SES feeder with 4/0 aluminum.

    Currently waiting for SRP to send the interconnection agreement. **RANT**Why do they wait to send it until after the AHJ inspection? Do they think for some reason you won't want to use your new PV system? Fails the common sense test. **END RANT**

    SunRenu has been extremely professional and helpful so far. The "only" snag they couldn't overcome was the 245watt panels not being available after we signed the contract. They were able to find 244watt panels that had similar specs so I was satisfied. My "add ons" for the extra strings and a/c combiner panel were met with several questions (clarifying what I really wanted) and a positive "they will do it" attitude. Highly recommended!!

    Next up is to reinstall the energy monitoring system.
  • solarvicsolarvic Solar Expert Posts: 1,051 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048

    In my case it seemed The people that wotked for the power co arent very cordinated. I live in Western Pa. The engineer that approved my plan was in new jersey and went on vacation for about a month between thanksgiving and Christmas. I wanted to get it online so I could get the tax break as that year was the last full year I was working before retirement. i keep sending emails and called. I kept getting message that engineer was on vacation. Finally after calling Someone in the engineers office finally sent me an email it was approved and just get it connected. Nothing official at all, just an email. So I just got it online Dec 24th that year. Even the woman that come to put the smart meter didn,t know for sure what to do. She called her boss and I explained the system to him. He told her to go ahead and change the meter. The woman that put the meter in said I was the first customer in her teritory that had a solar GTI system and most of them weren,t too familiar with them. Electrician never did one before. I had to point out a couple mistakes he was going to make. Then when inspecter come he hadn,t ever inspected a solar system before. So I had to gve him a tour and explain how it worked. Next problem is when I got my first electric bill. I was on automatic pay billing from my credit card. It was really messed up. When I called them they told me thier sofrware wasn,t able to work with gti billing and I would have to go back to standard billing. My bill comes from Akron ohio about 10 days later than my daughter accross the road even though we get meter read the same day. Seems like they have a problem with standard billing ads the bill always has white out with new numbers typed in. I dread estimated billing for the months that I get an estimated bill. Otherwise everything is running smoothly as far as I can tell. :Dsolarvic:D
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: 10.736kW Enphase system with 11 "strings"
    I chose SunRenu, a local company, to install my system. They were not the cheapest. They were willing to install what I wanted, an Enphase system with 44 panels. After the discussions here, I decided to have them installed with 4 panels/inverters to a string, with 11 strings coming together in an AC combiner panel in the garage.
    Why so many strings? The M215 inverters can handle up to 17 inverters per branch - the only reason I can think to limit to just 4 per branch is if you were really aiming to minimize voltage drop or each group of 4 panels were physically isolated. You sure you don't have 4 strings of 11 panels? How many circuit breakers do you have in your combiner panel?
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.736kW Enphase system with 11 "strings"
    drees wrote: »
    Why so many strings? ... ... How many circuit breakers do you have in your combiner panel?

    I plan to add battery backup or a UPS in the future. The discussion on the forum convinced me that running all 44 panels through a XW6048 without a large battery is unwise. With 11 strings of 976watts (4x244watts) I can incremently add PV supply to the AC coupled inverter until I find the sweet spot. I have 11 breakers in the AC combiner panel.

    The next goal is the keep the lights/AC on when the power goes down. SRP has been very reliable, outages are measured in minutes, not hours. So a smaller battery should be ok. I still need to get accurate peak power consumption data to ensure I size the inverter/UPS and batteries properly to meet expectations. More power & higher cost vs fewer loads & lower cost. Everybody wants it to be low cost!!

    Currently considering the XW6048 or the new Outback Radian GS8048 (900-0021-01-00 Rev A, installation manual). Both look promising. It appears the manufacturers are getting better at AC-coupling, GT and battery backup. I would include the Sunny Island if a single unit provided 240VAC split phase.

    Waiting on SRP to comission the system, then I can reinstall the energy monitoring system. So I have time before the purchase of the XW6048, GS8048 or next new inverter. Maybe Nissan will come through with http://www.nissan-global.com/EN/NEWS/2011/_STORY/111004-01-e.html and I can use the car battery.
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: 10.736kW Enphase system with 11 "strings"
    Maybe Nissan will come through with http://www.nissan-global.com/EN/NEWS/2011/_STORY/111004-01-e.html and I can use the car battery.
    It would be awesome to be able to use my LEAF to store energy for power outages. Heck, if I could use my Prius that would still be useful for an extended power outage - it's an efficient, clean and quiet generator.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.736kW Enphase system with 11 "strings"
    drees wrote: »
    It would be awesome to be able to use my LEAF to store energy for power outages. Heck, if I could use my Prius that would still be useful for an extended power outage - it's an efficient, clean and quiet generator.

    I am not planning to go off grid (yet), just something to keep the lights & A/C going for a few hours or possibly overnight. Just have to settle the question of kwh needed. And if it is worth paying for.

    I was hoping to have the interconnection agreement already. But it still hasn't showed up in the mail box. It is very difficult to be patient at this point!!

    The local Nissan dealer sent me an email saying they had two Leafs available for sale. My wife loves driving our Leaf to work, lunch and home. Generally a short 1.5 hour charge and it is topped up. She really likes :DNOT:D buying gas for it. We do have another gas car for driving out of town.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048

    From talking to others the idea of using Solid State Relays (SSRs) to turn off/on a string of micro inverters will work. I found a commercial controller that should work, it is expensive for occasional use.

    The SSRs can be operated by almost any digital system. Is this the forum for discussing automated control of a GT system?
  • mike95490mike95490 Solar Expert Posts: 8,234 ✭✭✭✭✭
    Re: 10.78kW Enphase system and XW6048
    ...Is this the forum for discussing automated control of a GT system?

    It's a lot better than the antique steam engine forum
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048

    it's ok either right here, as it is your thread, or start a new thread if you like.:D
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 10.78kW Enphase system and XW6048

    If it gets too technical (circuit design and such) it can go to a new thread under "Advanced".
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048

    I was looking at the Outback Radian GS8048 and comparing to the XW6048.
    Does anyone have any experience with the GS8048 yet? It looks good on paper although the surge rating times seem short compared to the XW6048.

    I'm thinking the XW6048 appears better than the GS8048.

    Still working on a low cost method of controlling the SSRs to try and match production to load.
  • jaggedbenjaggedben Solar Expert Posts: 230 ✭✭
    Re: 10.78kW Enphase system and XW6048

    RK,

    You should look at this thread on the Enphase forum...

    http://community.enphaseenergy.com/enphase_energy_community/topics/are_enphase_microinverters_grid_tie_only
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: 10.78kW Enphase system and XW6048
    Still working on a low cost method of controlling the SSRs to try and match production to load.

    For a low cost DIY approach you could use a cheap microcontroller like the arduino, then group the enphases into strings to reduce the number of SSDs, e.g. 10 strings of 1kW each.
    Then connect DC current sensor to microcontroller between the XW and the battery and program the microcontroller with something like:
    If it detects more than 1kW going to the battery, then turn off an enphase string.
    If it detects more than 1kW leaving the battery, then turn on an enphase string.

    IMO, the XW is a better choice than radian for this type of setup because you always have the frequency shifting to fall back on should any of the SSRs or the microcontroller fail.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048
    jaggedben wrote: »

    I read through the thread. I like the XW better than the MagnaSine. It is good to see more info regarding AC Coupling. The manufacturers are responding, slowly, but they are responding. It would be great if Enphase came out with an Islanding inverter specifically designed to work with their micro inverters.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    10.736kW Enphase system, XW6048 and PV control
    stephendv wrote: »
    For a low cost DIY approach you could use a cheap microcontroller like the arduino, then group the enphases into strings to reduce the number of SSDs, e.g. 10 strings of 1kW each.
    Then connect DC current sensor to microcontroller between the XW and the battery and program the microcontroller with something like:
    If it detects more than 1kW going to the battery, then turn off an enphase string.
    If it detects more than 1kW leaving the battery, then turn on an enphase string.

    IMO, the XW is a better choice than radian for this type of setup because you always have the frequency shifting to fall back on should any of the SSRs or the microcontroller fail.

    I started looking at the Ardunio Uno http://www.adafruit.com/products/325 as a controller. It has 14 IO pins to handle the 11 strings of inverters and 6 analog IO pins I could use for current/voltage/power sensing.

    I think I can open one leg of the 240VAC from the micro inverters and it should drop off due to lack of sync. Have to verify. And I have to verify the GT inverters will sync up to the grid through the SSRs.

    I was hoping to sense current for the PV array & for house consumption (at the Islanding inverter AC side). That way I could compare current to current without needing to measure voltage or power. If I measure both of the the 240VAC legs on the PV array & both legs of the 240VAC on the Islanding inverter...

    I made an assumption that might not work. I was planning on blocking the Islanding inverter from charging the batteries with a high current diode. Then adding a regular 240VAC (120VAC?) to 48VDC battery charger. Measuring the battery power flow may be the way to go. The current sensor will need to be much larger... but only one would be needed.

    The combination of PV control and a regular battery charger should minimize the cycling of the battery.

    There are a lot of assumptions needing to be proved.

    Having the frequency shift of the XW as a backup is a very good idea.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    10.736kW Enphase system, XW6048 and PV control

    Measuring current and/or power consumption:

    I have a Brultech energy monitoring system which works very well for monitoring and displaying power monitored. And it will monitor 7 channels. You can aggregate several breakers on a single channel if you keep the polarity the same, which is easy to do with US 240/120VAC split phase power. That does not translate into controlling that power easily.

    What I am proposing is to use an Arduino Uno processor with 4 current [URL="[url]http://www.allegromicro.com/en/Products/Part_Numbers/1301/index.asp[/url]"]sensors[/URL] to measure the power consumed & produced to control the SSRs that will enable/disable the strings of micro inverters. A string of micro inverters has 976watts=4 x 244watts DC production. A variable diversion load of up to 1500 watts should be adequate to keep the GT inverters on line. I plan to "cheat" by measuring 240VAC at two points, that way I can get away with measuring only current and not need to measure to voltage. And I don't need to calculate power.

    From a testing standpoint this is easy to do. I can stay grid tied while I do my testing!
  • dreesdrees Solar Expert Posts: 481 ✭✭✭
    Re: 10.736kW Enphase system, XW6048 and PV control
    I have a Brultech energy monitoring system which works very well for monitoring and displaying power monitored. And it will monitor 7 channels. You can aggregate several breakers on a single channel if you keep the polarity the same, which is easy to do with US 240/120VAC split phase power.
    I've been looking at the Brultech for energy monitoring - could you start a thread detailing your setup and how you like it?
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.736kW Enphase system, XW6048 and PV control
    drees wrote: »
    I've been looking at the Brultech for energy monitoring - could you start a thread detailing your setup and how you like it?

    Yes, I can start a Brultech thread.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048

    The Electric company came out and green tagged the system!!!

    Another step closer to PV commissioning. The SRP interconnect agreement that they mailed to the house was delivered today. The document inside was dated...
    9/16/11:grr and they had to wait to send it me? Because now I have to wait for them to receive my signed copies back in the mail. Original signatures only, you cannot print, sign, scan (or fax) and email.

    But they should schedule the commissioning within 10 business days of receiving the signed agreement. So it is another step closer.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    10.736kW Enphase system, XW6048 and PV control

    Today I ordered the parts to put together a control system for the strings of micro inverters, everything should be delivered the by Dec 7th.
    I ordered:
    1 - Arduino Uno, comes with 14 digital IOs and 6 analog IOs
    6 - Allegro A3503 ratiometric hall effect sensors
    22- Fotek SSR-25da, dc control, 240VAC 25amp load

    The general plan is to have the Arduino use 11 of the digital IO lines to control the SSRs in pairs to break/make both legs of the 240VAC from the micro inverters. It should be able to directly control them as long as the current draw is less than 40mA per pair, looks like 2 x 7.5mA - 15mA. The Arduino will use 4 of the analog IO lines to read 4 of the A3503s in 2 pairs, one pair on the PV wires to the feed back breaker and one pair on the inverter AC 240VAC wires. Since the micro inverters and islanding inverter will be synced up, the voltage will be the same. Measuring the current should be enough to get an accurate measure of the power balance.

    The A3505s are obsolete and not made any more. So I ordered 6 in the event one or two get broken. I can always buy the A1302 as a back up plan. Have to come up with a way to calibrate the A3503s. I'll probably tie wrap the sensors directly to the wires so they cannot more after calibration.

    The Foteck SSR-25DA are way more than I needed. I needed 120VAC & 1amp SSRs. I was looking at 240VAC & 3amp SSRs as having the extra margin I wanted. When I went to purchase them I saw the 380VAC & 25amp SSR-25DA for less than half what I was going to pay.

    I will need to test all of the SSRs for proper "turn off/on" and the A3505 sensors will to be tested for operation as well. The Arduino I bought as part of an experimenters kit. I plan to "practice" with the Arduino using the kit components then move to the power components.
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: 10.78kW Enphase system and XW6048

    Good luck with this project, I think it would be very useful if you get it working as every other day there's someone on this forum looking for a cheap way to have a battery backup system with a grid tied inverter.

    Could be useful to stick some LEDs inline with the SSRs so that you can clearly seen if they're on or off.

    Keep us posted on the progress :D
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048
    stephendv wrote: »
    Good luck with this project, I think it would be very useful if you get it working as every other day there's someone on this forum looking for a cheap way to have a battery backup system with a grid tied inverter.

    Could be useful to stick some LEDs inline with the SSRs so that you can clearly seen if they're on or off.

    Keep us posted on the progress :D

    Thanks for the encouragement. With my configuration of 4 micro inverters on a string I am confident I can make it work. It is a matter of how smooth the control will be. Putting leds on the SSRs for a local/backup means of checking operation is a good idea. Do to the past assistance of those on the forum, I feel it is appropriate to post back with status reports.

    I am still exploring the use of a current blocking method as well. That would allow the use of a different battery charger and potentially different battery technology (the successor to the LiOn). The advantage there is that would allow someone with a string inverter to use battery backup as well.

    SMA does have the lead in this area. If they produced a Sunny Island with US style 240VAC split phase that would be the item to purchase to provide battery backup to an existing grid tied system.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    10.736kW Enphase system, XW6048 and PV control

    I may have purchased the SSRs too soon. While working on a flowchart for the controller, I realized that there may be an advantage to using Current Transformers (CTs).

    The instructions for my Brultech energy monitoring system state you need to put the CTs monitoring 240VAC legs on "facing" opposite directions to measure total current of both legs. If you install both CTs facing the same way (see attached jpg) the induced voltages tend to cancel each other and you get either a zero amp or very low amp reading.

    I might be able to use that to simplify my sensing circuit. If I use 2 pairs of CTs, I can use 1 pair on the "same" leg of both the PV & the Islanding inverter "facing" the same direction to directly sense differential current and use the other pair of CTs on the other "same" leg of the PV & the Islanding inverter to do the same. Adding the two together would give net current flow and direction.

    The jpg is from the Brultech installation booklet. I could not find a public link to the booklet.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    10.736kW Enphase system, XW6048 and PV control

    Things are coming together for the commissioning appointment. SRP scheduled the appointment for 8:30 am 11/10!!

    It is fairly exciting! Of course my wife is not nearly as exuberant about it... But we are finally going to join the ranks of those insulated from future rate hikes by the Electric Co!!

    The real selling point for us was the investment market we are enduring. By "investing" in PV I will get about a 10% return. And it is a SAFE investment!!
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.736kW Enphase system, XW6048 and PV control
    I may have purchased the SSRs too soon. While working on a flowchart for the controller, I realized that there may be an advantage to using Current Transformers (CTs).
    Oops. I meant to say the A3503 ratiometric Hall Effect sensors instead of SSRs.:blush:
    The instructions for my Brultech energy monitoring system state you need to put the CTs monitoring 240VAC legs on "facing" opposite directions to measure total current of both legs. If you install both CTs facing the same way (see attached jpg) the induced voltages tend to cancel each other and you get either a zero amp or very low amp reading.

    I might be able to use that to simplify my sensing circuit. If I use 2 pairs of CTs, I can use 1 pair on the "same" leg of both the PV & the Islanding inverter "facing" the same direction to directly sense differential current and use the other pair of CTs on the other "same" leg of the PV & the Islanding inverter to do the same. Adding the two together would give net current flow and direction.

    After more thought, I can use 1 pair of CTs to measure the net current flow directly. I can take advantage of the cross current "cancelling out" concept to give a direct reading net current. Prior I was talking about using a CT on each wire and connecting them in series "backwards" to electrically cancel out the measurement. Using the conductors directly does the same thing and it uses one CT instead of two.

    Then I "properly" wire the 2 CTs together in series and directly measurement net current in or out of the Islanding inverter.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    10.736kW Enphase system with 11 "strings"

    It's ALIVE!!

    SRP came out this morning and commissioned my PV system. I am out of town and could not witness it personally.:cry:
    John from SunRenu sent me some pictures showing the PV meter being installed just to whet my appetite until in can stand there myself.

    SunRenu said they would do their best to get the system commissioned before Thanksgiving. And they delivered!! RECOMMENDED to anyone in the Phoenix metro area.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048

    congrats. too bad you couldn't have been there to see it.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048
    niel wrote: »
    congrats. too bad you couldn't have been there to see it.

    When I evaluated the PV installers, most told me 4-6 months to commission the system. SunRenu said 3-4 months to commissioning and they hit it at a week past 3 months. I did actively encourage them at almost every step along the way.:p
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048

    The concept has been proven to work!! But I wasn't the one that did it first. Mr. Robert Greene has that honor. Here is his write up: http://www.greeneselectric.com/Off-Grid_Power_with_Enphase.ppt. I had to put my AC coupling project on hold while dealing with numerous other issues. Gotta work to pay the bills. His success does give me incentive to get started again.

    I am very happy with my PV system. My electric bill has been $16.51 for the last several months. That's the SRP $15 minimum service charge plus all the fees and taxes.
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