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  2. AC Coupled Systems • Growing market segment • Can be confusing! • Can be complicated! • Numerous ways to go • MidNite has taken most of the mystique out of the equation

  3. One inverter capable of AC couplingThe SMA Sunny Island is the most difficult inverter to hook up to pass inspectionMore on that later

  4. OutBack inverters were the first to AC couple, but each inverter is only 120VAC • Grid tie inverters are 240VAC • 2 inverters required in this setup

  5. It is interesting to note that 90% of this system would be the same for off-grid or battery backed up grid tie. Can you tell which type this is?

  6. 120V Magnums are also not easy to AC couple

  7. Yes, you can even screw up a MidNite E-Panel for the XW inverter. This is functional, but messy

  8. Before we show how to make AC coupling easy, let’s see just what AC coupling is

  9. Why AC Couple1. a way to use those expensive grid tie solar panels during a power outage2. Provides limited power during a power outage3. Allows the installer to go visit their grid tie customers with something useful to sell

  10. What is AC Couple • AC Coupling is a controlled back feed to a battery based inverter • A back feed is hooking up AC to the output of an inverter • Normally when you back feed an inverter, they blow up (try it sometime, smile) • AC coupling is a synchronized back feed • The grid tie inverter shifts frequency to match the battery based inverter before connecting. This makes it ok to do

  11. AC Coupling of inverters • Battery-less grid tie inverters require a grid to be connected before they will turn on. The grid must meet certain voltage and frequency parameters. • You have all heard about anti-islanding requirements that the inverters must meet • Battery based sinewave inverters can meet these requirements • Inverters do not need to be grid tie listed

  12. AC Coupling of inverters • Not all battery based sinewave inverters are capable of backfeed. • Your choices in North America are: • SMA Sunny Island • Outback FX, VFX and Radian • Magnum PAE series • Schneider XW series

  13. SMA Sunny Island

  14. AC Coupling of Inverters • The Sunny Island and Sunny Boy communicate with each other to insure proper battery charging during a power outage. • No other inverter combination can claim this

  15. SMA Sunny IslandSince the Sunny Boy output is 240VAC and the Sunny Island input is 120VAC, a step down autoformer is used

  16. SMA Sunny IslandNotice that the output of the SB connects to the output of the SIThe autoformer changes 240V to 120V

  17. SMA Sunny IslandThe SI inverter has only one AC input. We provide an optional ATS that5 fits inside our SMA E-Panel

  18. The Sunny Island/Sunny/ Boy combination was designed to be AC CoupledThey thought of everything(from a European point of view)

  19. SMA in Germany still has problems with the US NEC code. The Sunny Island is not easy to install to meet code

  20. SMA had been requesting that MidNite Solar make them an E-Panel for years. We finally didWe did not realize how big a deal this was going to be!

  21. The pre-wired system shown here is as plug and play as they comeThe top piece is the autoformerBattery box and cabling is included and drop ships where you want it

  22. E-Panel with ATS option installedAll SMA E-Panels come wired for 240VAC (2 SI inverters)

  23. E-Panel shown with AC bypass switch, 500 amp shunt and sub panels breakers installed

  24. Dual systems do not require an autoformer

  25. Need a large AXC coupled system?

  26. We even designed a 1000 amp battery combiner for this system

  27. SMA AC Coupled systems • SMA AC Coupled solutions for 1 to 4 inverters • 4,500 watts to 24,000 watts • Purchase pre-wired and tested or parts • Remember those tech service people we mentioned? You may need to involve them on your first system.

  28. Enphase AC Coupled systems • Enphase systems are pretty much the same as all others • When using a Magnum PAE inverter, you must limit the PV array to less than 4000 watts. • Failure to do this will result in inverter failure • Magnum is the easiest for Enphase AC coupling

  29. This exact system is now on our price list and available for order

  30. The disco combiner is there for reference onlyWe do have a three string AC disco combiner

  31. The Grid Tie inverter shown can be Enphase or any 240VAC grid tie up to 4000 watts of actual output

  32. Since the two different inverters have no communication, we install a SSR to knock the grid tie off line as required

  33. This is a pictorial wiring diagram

  34. Uncontrolled battery charging • Magnum and OutBack inverters charge batteries from AC connected to their outputs • The inverters sense circuits that control charging are on the AC inputs not the output, therefore cannot control charging • These inverters charge wide open and cannot taper off. • A relay is required to disconnect the GT

  35. Uncontrolled battery charging • SMA has controlled battery charging and tapers off as the batteries get charged • This requires that the AC coupled system is comprised of a Sunny Island and Sunny Boy. They were designed to work together. • No external relay required

  36. Uncontrolled battery charging • Schneider WX shifts frequency to knock the grid tie inverter off line for 5 minutes. • The XW does this with any brand grid tie inverter, but battery charging does not taper off. • No external relay required

  37. Uncontrolled battery charging • OutBack inverters do not taper off like the SMA, nor do they shift frequency like the XW • You must add an external relay between the grid tie inverter and the battery based inverter • The OutBack aux output can supply the power & control to drive an external relay

  38. Uncontrolled battery charging • Magnum inverters do not taper off like the SMA, nor do they shift frequency like the XW • You must add an external relay between the grid tie inverter and the battery based inverter • The Magnum router can supply the control to drive an external relay, but not the power

  39. The solid state relay eliminates battery over charging

  40. Hook up the output from your grid tie inverter here

  41. Hook up the sub-panel hereThis is the AC output of the inverter

  42. Hook up the mains utility connection here

  43. Hook up the neutral and ground connections from the main distribution panel here

  44. 4000 watt limit • This limit only applies during power outages • We have another method that allows larger arrays, but reduces the array power during outages • This is a radical modification, but works

  45. A solid state relay is placed inside the combiner to reduce quantity of strings

  46. This is a self contained pre-wired AC coupled system

  47. All wiring is behind the breaker panel

  48. All required over current and disconnects are in place, wired and tested

  49. Multiple battery configurations available. Shown is just one

  50. The enclosure for this system is made from aluminum and is suitable for outdoor locations