Swapping out failed inverter without DC shutoff to panels

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • barneyfoot
    Junior Member
    • Jun 2020
    • 13
    #1

    Swapping out failed inverter without DC shutoff to panels

    I'm going to swap out a failed Xantrex 4KW inverter with a new Sunny Boy 3.8KW. There is no DC shutoff to the panels.

    Can I safely do the swap using existing DC connectors since I won't be working with exposed wire? The array is rather large so there's no easy way to cover it from sun.

    Of course there is AC shutoff that I will be using.

    Attached photo of the existing DC connectors (both to old and new). My other Xantrex was previously replaced by a solar professional so I plan to use his install for reference.

    Thanks in advance.

    Note - couldn't upload attachments so photo links are here:

    old
    Page Not Found
    https://drive.google.com/file/d/1pbKQ1PvlrfD0mze8GGSDgJy3_y_udg90/view
    Web word processing, presentations and spreadsheets


    new
    Page Not Found
    https://drive.google.com/file/d/1pg1Xxw6hK3wbjgC7AryeXgdMnYoOOcLd/view
    Web word processing, presentations and spreadsheets

    Tags: inverter, shutoff
    • peakbagger
      Solar Fanatic
      • Jun 2010
      • 1565
      #2
      If I doubt, do it at night with a headlamp.

        Comment

        • solarix
          Super Moderator
          • Apr 2015
          • 1415
          #3
          1) Turn off the AC.
          2) Go on roof and disconnect one panel from each string.
          3) Measure voltage on DC conductors at inverter to make sure you got step 2 correct.
          4) Swap inverters.
          5) Reconnect the array.
          6) Measure voltage on DC conductors at inverter to make sure you got step 5 correct.
          7) Turn on AC and check inverter for correct operation.

          or Buy an expensive pair of electrician's gloves and get-r-done.

          or Just carefully tape the DC conductor's ends as you remove them and be careful as you do the swap.

          I've done all three methods over the years - and you pays your money, you takes your choice.
          BSEE, R11, NABCEP, Chevy BoltEV, >3000kW installed

            Comment

            • Mike90250
              Moderator
              • May 2009
              • 16020
              #4
              i'd do it at night, and while I was at it, install a DC shutdown. If the inverter ever fails in a bad way, you have no way to disconnect 3kw of DC feeding the fire
              Powerfab top of pole PV mount (2) | 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

                Comment

                • Ampster
                  Solar Fanatic
                  • Jun 2017
                  • 3650
                  #5
                  Fortunately that looks like a ground mount so you have easy access to the panel connectors. They should only be disconnected when there is no load. Shutting down the AC should do that. The switch on the bottom if the Xantrex is a convenient place to do that, but remember to also shut off the breakers at the service panel so there is no power on the AC conductors inside the inverter.
                  9 kW solar, 42kWh LFP storage. EV owner since 2012

                    Comment

                    • Mike90250
                      Moderator
                      • May 2009
                      • 16020
                      #6
                      Turning off the AC power should (in theory) cease most of the DC current from the solar array. But dealing with a failed unit, it's tough to say that this would be a safe way to proceed. String inverters often run 400-500VDC which, if the inverter is consuming any DC power, will arc (ruin) the connections as you make and break them.

                      Connecting the new unit, there is very likely some capacitance inside the inverter, which will draw a brief arc as the final connection is made. Again, damaging the conductor.
                      Powerfab top of pole PV mount (2) | 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

                        Comment

                        • Ampster
                          Solar Fanatic
                          • Jun 2017
                          • 3650
                          #7
                          That is good advice. If this is the old style Xantrex GT inverter the switch at the bottom is an AC/DC disconnect. Check the manual and the internals to verify.
                          9 kW solar, 42kWh LFP storage. EV owner since 2012

                            Comment

                            • barneyfoot
                              Junior Member
                              • Jun 2020
                              • 13
                              #8
                              Originally posted by Ampster
                              That is good advice. If this is the old style Xantrex GT inverter the switch at the bottom is an AC/DC disconnect. Check the manual and the internals to verify.
                              Yeah, it has a switch but I'm assuming the wires from array are live if I'm doing it during daytime right? If so then maybe I just need to work in evening or early morning and git r done.

                                Comment

                                • Ampster
                                  Solar Fanatic
                                  • Jun 2017
                                  • 3650
                                  #9
                                  Originally posted by barneyfoot

                                  Yeah, it has a switch but I'm assuming the wires from array are live if I'm doing it during daytime right? If so then maybe I just need to work in evening or early morning and git r done.
                                  Yes they will be live. The switch should remove load so that you can disconnect a connector at the panel and remove voltage as suggested above. Nightime would be safer if you are not comfortable with determining whether there is any current. Load is what causes current to flow. A clamp DC Amp meter would tell you if there was current flowing. If in doubt, call your electrician.
                                  9 kW solar, 42kWh LFP storage. EV owner since 2012

                                    Comment

                                    • Mike90250
                                      Moderator
                                      • May 2009
                                      • 16020
                                      #10
                                      The vintage XW's had an issue with the "bottom of the unit DC switch" failing. There was even a recall on them, a new part was issued and could be swapped in. I was there !

                                      Still does not solve the connecting to the new inverter, which will have input circuits to charge.
                                      Powerfab top of pole PV mount (2) | 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

                                        Comment

                                        • barneyfoot
                                          Junior Member
                                          • Jun 2020
                                          • 13
                                          #11
                                          Originally posted by solarix
                                          1) Turn off the AC.
                                          2) Go on roof and disconnect one panel from each string.
                                          3) Measure voltage on DC conductors at inverter to make sure you got step 2 correct.
                                          4) Swap inverters.
                                          5) Reconnect the array.
                                          6) Measure voltage on DC conductors at inverter to make sure you got step 5 correct.
                                          7) Turn on AC and check inverter for correct operation.

                                          or Buy an expensive pair of electrician's gloves and get-r-done.

                                          or Just carefully tape the DC conductor's ends as you remove them and be careful as you do the swap.

                                          I've done all three methods over the years - and you pays your money, you takes your choice.
                                          This whole thread has been really helpful. I think what folks are saying is that as long as both inverters have DC shutoff (which they do) I should be able to swap without issue. As long as there's no load then I'm fine. I'll be sure to test with a clamp meter. Will probably pick cloudy day or low light morning evening just to be safe.

                                          My initial post was due to concern about not having a DC shutoff switch between array and inverter.
                                          Last edited by barneyfoot; 12-28-2020, 01:18 PM.

                                            Comment

                                            • Mike90250
                                              Moderator
                                              • May 2009
                                              • 16020
                                              #12
                                              Most clamp on meters are pretty lame below an amp. half an amp @ 400V is still 200w of HV DC arc. Or it may work out fine
                                              Powerfab top of pole PV mount (2) | 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

                                                Comment

                                                • bcroe
                                                  Solar Fanatic
                                                  • Jan 2012
                                                  • 5203
                                                  #13
                                                  Put out a big work light and do it in the night. To make that and other work easy, I have regular
                                                  120VAC outdoor outlets mounted about every 70 feet along the back. Bruce Roe

                                                    Comment

                                                    Previous template Next
                                                    Working...