External Bypass Possible with Conext SW?

chrismorischrismoris Registered Users, Users Awaiting Email Confirmation Posts: 7 ✭✭
Hello,

I have an on-grid solar system that I would like to add a battery system to.

Current Setup

  • 200A service --> 200A exterior sub w/ 20A solar feed-in --> 200A interior main panel w/ loads
  • 3.8 kW, 20A power-one inverter from 2013 (probably doesn't support frequency-droop)

Desired Outcome

  • 200A service --> 200A transfer switch --> 200A exterior sub w/ 20A solar feed-in --> 200A interior main panel w/ loads
  • Schneider SW4048 with 15 kWh or so of LFP batteries
  • 3.8 kW, 20A power-one inverter from 2013 (probably doesn't support frequency-droop)

I want to be able to disconnect my entire home from the grid and power it from a combination of the Conext SW4048 and my existing solar inverter. I realize that I wouldn't have enough capacity to run a dryer or other heavy loads, but I don't have AC and rarely see over 4 kW of loads, average consumption is 20 kWh/day.

To do this I would like to use the Conext SW4048, but do not want to rewire portions of my home onto the backup bypass. I would like to island the whole home.

Is it possible to configure the Schneider products to work with an external transfer switch rather than limiting your backup loads to 60A (or whatever the limit is)? If so, what kind of transfer switch is needed and how do the communications work?

Thanks!

Comments

  • mcgivormcgivor Solar Expert Posts: 3,815 ✭✭✭✭✭✭
    Welcome to the forum 

    What is the rationale and intent behind the proposed system, competing with grid costs using batteries will in most cases result in net loss.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • chrismorischrismoris Registered Users, Users Awaiting Email Confirmation Posts: 7 ✭✭
    I live in an area where we get power outages during fire season. 2-3 per year if not more. Recently I lost power for two days. I have the solar system already (4.5 kWdc grid-tied), I'd just like my home to stay powered during an outage. I don't mind the cost.

    I figure my BOS would be about:
    -- Conext SW4048 - $1400
    -- 15 kWh of Lishen LFP cells in 16s for 48 or so volts - $1500
    -- TBD 200A rated transfer switch - $1000?
    -- Enclosure for storage - $500

    For $4000 or so I could get home backup with this setup (in theory). Am I missing something?

    The question is pretty specific about how to network the Conext to work with an external transfer switch. This would imply the AC1 (or AC2?) ports would actually feed the whole home instead of a critical loads sub. Has this been done? I am almost positive it is a standard configuration for the XW but I don't know about the SW.
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,910 ✭✭✭✭✭
    edited April 18 #4
    CSW is only 30 A . XWP is 60  A  Bypass. These are both mechanical switching for bypass and/or electrical depending on what you program. You can wire just about anything to externally bypass as long as it is safe. If you have insurance for the home, it needs to be inspected. It could be a way to deny an insurance claim if it is not done correctly.

     I will add that I have seen insurance denied even if the cause of the fire was not the power system. Be Safe and have it all documented if insurance is a value to you!.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • chrismorischrismoris Registered Users, Users Awaiting Email Confirmation Posts: 7 ✭✭
    CSW is only 30 A . XWP is 60  A  Bypass. These are both mechanical switching for bypass and/or electrical depending on what you program. You can wire just about anything to externally bypass as long as it is safe. If you have insurance for the home, it needs to be inspected. It could be a way to deny an insurance claim if it is not done correctly.

     I will add that I have seen insurance denied even if the cause of the fire was not the power system. Be Safe and have it all documented if insurance is a value to you!.
    Thanks Dave. That is the one big factor still on my mind (insurance).

    Wish respect to wiring the external bypass, how would you go about doing that in technical terms? Does the SW then just attach on the AC side only to AC2 without using the AC1 ports? Or does the inverter supply a voltage source on AC1 automatically if AC2 isn't populated?

    Thanks
  • BB.BB. Super Moderators, Administrators Posts: 31,684 admin
    Chris,

    There are several methods that could work.. From what I can see. It does also depend on what you really expect from the system. The more your "go around" your inverter-charger, the fewer "automation features" you can take advantage of with the inverter-charger.

    • Get a manual or automatic transfer switch and tie AC msecains to one input, and Inverter out to the other... Will you want a backup genset, what happens if somebody does try running the drier, well pump, hair drier, electric room heater, microwave all at the same time--Pop breaker/shutdown inverter)? If backup genset--Sized to run the inverter-charger, or sized to run the whole home (including larger AC loads)? Where to connect genset (to AC2 input of inverter, AC1 to AC mains to backup charge battery bank, etc.). Use inverter AGS function? Use inverter's ability to limit genset loading during heavy AC loads?
    • Install a sub panel. Move all "critical wiring" from AC main panel to sub panel... Connect inverter from AC main panel to sub panel on AC1 input. And genset on AC2 input--Run sub panel loads from inverter+.generator.
    • May be a bit of a "cludge"--But I think it is legal. Get a manual transfer switch that has 6 or more AC branch circuits. You connect AC xfer inputs to main panel branch circuit breakers, and xfer switch to protected branch circuits. Connect inverter to "generator" xfer switch input. Connect Main Panel to inverter AC1 input (genset to AC2). Use manual xfer switch in "connect to inverter/generator" for normal operation, and option to switch to main AC power during service/inverter failures.

    https://www.homedepot.com/s/manual transfer switch?NCNI-5 (example of Home Depot up to 10 circuit AC manual transfer switches)

    The last one is (possibly) an easier/cheaper way to get the equivalent of a protected sub-panel without adding a new sub panel and transfer switch.

    The CSW has its own auto transfer switch--Adding a second external automated transfer switch seems to be redundant and gives you fewer integrated functions.

    Are you planning on adding solar charging to the battery bank, or just use genset/AC mains?

    Anyway--Dave knows much more about this than I... Just some suggestions of how you can look at your various options. Adding a 200 AH transfer switch for a 30 Amp CSW capable inverter/transfer switch rating--Just does not make a lot of sense--Unless you are adding a genset+switch for whole home.

    Keeping the system small(er), simple(r), and using the CSW (or similar) inverter-charger as it is designed can keep costs down and servicing easier/more sane.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Solar Expert Posts: 3,815 ✭✭✭✭✭✭
    edited April 19 #7
    The one potential stumbling block using the grid tied inverter, is when solar is needed the most during an outage, it's not available being the GT inverter needs an AC reference to operate and the transfer would isolate it anyway. Using a separate array along with a charge controller is one solution or diverting the existing array from the GT inverter to a charge controller during an outage is another, albeit involving  little more complexity.

    The method I would us is depicted in the single line diagram below, the theroy of operation is as follows:

    During normal grid available conditions the PV operates as always through the GT inverter feeding into the main distribution. The DC-AC inverter is always on, grid support maintains the battery in float, inverter programed to not sell to preserve battery.

    When an outage occurs the ATS transfers to backup, the normally open auxillary contact makes thus sending battery voltage to operate a DC coil of a DC contactor, this transfers the PV to a charge controller which is normally in night mode, powered by the battery. This allows the battery to be charged during extended outages along with powering loads as needed.

    When grid is restored everything returns to normal, the grid will recharge the battery if required, then maintain float. 




    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • chrismorischrismoris Registered Users, Users Awaiting Email Confirmation Posts: 7 ✭✭
    edited April 19 #8
    Thank you for the detailed diagram. I've adjusted it slightly and think that the following could work. I think it is a bit more simple, but I'm not sure about a few things:

    Grid Connected (Green Path)



    Off-Grid (Red Path)



    In this scenario the grid-tie, grid-forming, and utility grid are all connected via a new sub for the off-grid inverter which connects to the utility side of the ATS and ultimately the existing sub-panel and main. When the utility service disappears, the AC1 port of the off-grid inverter is de-energized and the ATS switches to feed from AC2. This moves all loads and the existing grid-tied inverter to the SW4048 grid-forming source. I don't think I need communications between the ATS and the grid forming inverter here. 

    Questions:
    • Is it possible to permit something like this or will I have issues with sizing of branch circuits, the LFP batteries not being UL9540, or anything else?
    • Do I need OCP between the AC2 port and the input to the transfer switch. If not, do I need to size the conductor from AC2 to service rating since the only protection in the chain is a 200A breaker at the sub? 
    • If I do need OCP, do transfer switches have at least one breaker space on the input lugs or will I need to drop in a fused disco?
    • In an ideal world the transfer switch could have 2 breaker spaces on each input which would then allow me to get rid of the new 200A sub since I could tie the utility feed and the 40A breaker for the grid-tie inverter to a single pole.
    • What transfer switches are economic and will get the job done here? Recommendations? I'm new to this.
    • Any safety concerns with the configuration?
    Thanks
  • BB.BB. Super Moderators, Administrators Posts: 31,684 admin
    edited April 20 #9
    To avoid possible confusion, as I understand the CSW has only ACin and ACout...

    Other inverters can have AC1 (utility power in/Grid Tie/Hybrid inverter support--if applicable) and AC2 (genset power in) (default). And ACout to loads...

    The CSW does all that with just ACin and ACout (and external AC transfer switch if needed for utility/genset connections).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • chrismorischrismoris Registered Users, Users Awaiting Email Confirmation Posts: 7 ✭✭
    BB. said:
    To avoid possible confusion, as I understand the CSW only ACin and ACout...

    Other inverters can have AC1 (utility power in/Grid Tie/Hybrid inverter support--if applicable) and AC2 (genset power in) (default). And ACout to loads...

    The CSW does all that with just ACin and ACout (and external AC transfer switch if needed for utility/genset connections).

    -Bill
    Hi Bill,

    Thank you for the clarification. I have reworked the diagram to show ACin and ACout as AC1 and AC2. Your definition is better and accurate, mine was probably not.

    Still wondering same questions in prior post.

    Thanks
  • mcgivormcgivor Solar Expert Posts: 3,815 ✭✭✭✭✭✭
    With AC coupling there are many considerations that need to be taken into account, such as not being viable with a split phase system due to unbalanced loads, DC coupled systems are in most cases easier to manage because it takes the GT inverter out of the picture. This link describes the pros and cons https://www.morningstarcorp.com/advantages-morningstars-dc-coupling-vs-ac-coupling-whitepaper/

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • chrismorischrismoris Registered Users, Users Awaiting Email Confirmation Posts: 7 ✭✭
    mcgivor said:
    With AC coupling there are many considerations that need to be taken into account, such as not being viable with a split phase system due to unbalanced loads, DC coupled systems are in most cases easier to manage because it takes the GT inverter out of the picture. This link describes the pros and cons https://www.morningstarcorp.com/advantages-morningstars-dc-coupling-vs-ac-coupling-whitepaper/

    Okay, I understand that, but I believe the SW4048 is a transformer based inverter which will derive a neutral for off-grid allowing for both 120 L-N and 240 L-L. I don't think that will be an issue here. The GT inverter I have is a 2013 vintage so it probably doesn't support frequency-droop, meaning it will probably just trip off on over frequency if the battery is fully charged. I am okay with this.

    Any issues with the diagram above for switching the whole home? Interested if anyone has thoughts on the transfer switch and the permitting questions for this type of setup.

    Thanks
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,910 ✭✭✭✭✭
    He is telling you that you may have issues with this small (30 A) of an inverter with your loads. You have not talked about what they are.

    Going from a 200 amp service to 30 amp requires you to address your loads. This is easy Offgrid as we do not even try to do some of the things that grid people do. Electric water heaters are off the table or they are used only during summer.

     Unbalanced loading is the sure way to lights out! Power goes out and a fault is generated.

    This is why XW is really what you want to use to keep this simple. Alot harder to be unbalanced at 60A.

    If you have a wildfire how much time do you think you are going to have for this?  Same with the Insurance, how are you going to address that? Take a permit out with your county? Do you have time to do all of that?  I know this might not be positive thinking, but some say a pessimist has more data.

    Fire season is here right now!  I use to say the south west is in Fire season/ Drought. This year it is anything west of the Mississippi.
     
    At least make sure you have a good Genset and a ditch plan so that your family is safe. Test it monthly and maybe have a spare!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • chrismorischrismoris Registered Users, Users Awaiting Email Confirmation Posts: 7 ✭✭
    He is telling you that you may have issues with this small (30 A) of an inverter with your loads. You have not talked about what they are.

    Going from a 200 amp service to 30 amp requires you to address your loads. This is easy Offgrid as we do not even try to do some of the things that grid people do. Electric water heaters are off the table or they are used only during summer.

     Unbalanced loading is the sure way to lights out! Power goes out and a fault is generated.

    This is why XW is really what you want to use to keep this simple. Alot harder to be unbalanced at 60A.

    If you have a wildfire how much time do you think you are going to have for this?  Same with the Insurance, how are you going to address that? Take a permit out with your county? Do you have time to do all of that?  I know this might not be positive thinking, but some say a pessimist has more data.

    Fire season is here right now!  I use to say the south west is in Fire season/ Drought. This year it is anything west of the Mississippi.
     
    At least make sure you have a good Genset and a ditch plan so that your family is safe. Test it monthly and maybe have a spare!
    Got it. That makes sense, 3.8 kWac is probably enough for my normal usage (gas heating, no use of A/C). I consume about 20 kWh a day. In either case, point taken on the XW -- So then for that inverter, does the single line above work / make sense? 

    The other option on easy street is to just go for a single powerwall 2.
  • mcgivormcgivor Solar Expert Posts: 3,815 ✭✭✭✭✭✭
    edited April 20 #15
    chrismoris said:!
    Got it. That makes sense, 3.8 kWac is probably enough for my normal usage (gas heating, no use of A/C). I consume about 20 kWh a day. In either case, point taken on the XW -- So then for that inverter, does the single line above work / make sense? 

    The other option on easy street is to just go for a single powerwall 2.


    Whilst it may work it, likely won't work well for a number of reasons which have been noted along with the fact that the ABB power one is not recommended for AC coupling, although you appear comfortable with it not working in the AC coupled mode. Here's another alternative utilizing a 600V DC transfer switch with built-in MPPT charge controller, courtesy Morningstar. The difference in your case would be the auto transfer switch wouldn't be feeding a critical load panel. Link to entire pdf attached. Sometimes it's worth spending a little to ensure better results, at least that's my opinion.


    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • mike95490mike95490 Solar Expert Posts: 9,274 ✭✭✭✭✭
    We've had 6 fires in the County this weekend, 2 are still burning.  Fire season started last week !!!!
    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 ,

  • Dave AngeliniDave Angelini Solar Expert Posts: 5,910 ✭✭✭✭✭
    edited April 20 #17
    Yep it is here!  We always say 2 weeks after the last rain in the Sierra. That was 6 weeks ago...

    The single line looks too complicated, not how I would do this. Could you explain the line to your wife or kids? The load of 20kwh is not what you really need at this early point. You need to know how balanced the 120vac loads are. If the big loads are all 240vac, then it is easier. If you have electric range, water heater, and dryer, too much work and another strategy is called for.

     Maybe the Powerwall would be good as it at least would be professionally installed. No DIY with Tesla. I did PM you.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

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