Announcement

Collapse
No announcement yet.

grounding question and confusion

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • grounding question and confusion

    I want to make sure when I install my system (planned for next weekend) that I do the grounding properly. I am installing 24 canadian solar 250 watt panels (two strings) on a flat roof building using the ecofoot ballast mounting system. My inverter is a sunnyboy 3800.

    For grounding I was planning on doing the following below. Please let me know if this makes sense.

    Use continuous length of 10 gauge bare copper wire on each string and have these separate ground wires terminate onto a ground bus bar in a combiner box on roof. A separate 8 gauge thwn green stranded wire will leave combiner box and go down through conduit to a dc disconnect where ground wire terminates onto a grounding lug. Then separate 8 gauge thwn grounding wire goes through conduit and terminates onto one of the ground terminals (ground symbol without circle around it) inside the sunnyboy inverter. Then from other ground terminal inside sunnyboy inverter (ground symbol with circle around it) 8 gauge thwn through conduit to AC disconnect where there is grounding bar. Then another length of 8 gauge thwn through conduit to ground bar in electric service panel.

    Does this make sense?

    Also, I am confused by the two grounding terminals in the sunnyboy inverter. One with the circle around it and one without. Is it correct to connect the ground wire from dc disconnect to the terminal with the ground symbol without the circle and to connect the ground wire that goes to the ac disconnect and then service panel to the terminal that has the ground symbol with the circle around it.

  • #2
    Nope
    One continuous #8 min or #6 preferred to run and bond to each module and run continuously to the combiner inverter and terminate on the building grounding electrode conductor any splices need to be of a type that is irreversable (crimped)
    NABCEP certified Technical Sales Professional

    [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

    [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

    [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

    Comment


    • #3
      Originally posted by mikael6 View Post
      I want to make sure when I install my system (planned for next weekend) that I do the grounding properly. I am installing 24 canadian solar 250 watt panels (two strings) on a flat roof building using the ecofoot ballast mounting system. My inverter is a sunnyboy 3800.

      For grounding I was planning on doing the following below. Please let me know if this makes sense.

      Use continuous length of 10 gauge bare copper wire on each string and have these separate ground wires terminate onto a ground bus bar in a combiner box on roof. A separate 8 gauge thwn green stranded wire will leave combiner box and go down through conduit to a dc disconnect where ground wire terminates onto a grounding lug. Then separate 8 gauge thwn grounding wire goes through conduit and terminates onto one of the ground terminals (ground symbol without circle around it) inside the sunnyboy inverter. Then from other ground terminal inside sunnyboy inverter (ground symbol with circle around it) 8 gauge thwn through conduit to AC disconnect where there is grounding bar. Then another length of 8 gauge thwn through conduit to ground bar in electric service panel.

      Does this make sense?

      Also, I am confused by the two grounding terminals in the sunnyboy inverter. One with the circle around it and one without. Is it correct to connect the ground wire from dc disconnect to the terminal with the ground symbol without the circle and to connect the ground wire that goes to the ac disconnect and then service panel to the terminal that has the ground symbol with the circle around it.
      A #10 equipment grounding conductor according to table 250.122 at the strings is generally of sufficient size because string wiring is usually #10, but some inspectors require #6 because they feel it may be exposed to physical damage according to 690.46 onto 250.120(C)...I would recommend #6 solid because grounding is so important up there where it is exposed and it is expected to last 20+ years. The NEC is a minimum standard.

      All grounding in the string inverter should be common. I don't know why there are separately identified terminals. Do a continuity test to see if they are in common.

      Be careful when running the grounding electrode conductor from the string inverter thru "conduit" as you have detailed. If the conduit is metal then it needs to be bonded everywhere the GEC enters and exits that conduit per 250.64(E)

      If the grounding electrode conductor is run under NEC article 690.47(C)(3) as a combined GEC/EGC, then your method of terminating at the bus-bar of the service panel is acceptable. Note: Some state incentive programs do not allow this method of grounding (MASS) to be used.

      I like Naptown's method of irreversible connecting the GEC to the buildings GEC. The grounding electrode conductor is the only wire that must be unbroken (irreversibly spliced) in the system grounding.

      All references per 2011 NEC

      shortcircuit

      Comment


      • #4
        Originally posted by shortcircuit2 View Post
        A #10 equipment grounding conductor according to table 250.122 at the strings is generally of sufficient size because string wiring is usually #10, but some inspectors require #6 because they feel it may be exposed to physical damage according to 690.46 onto 250.120(C)...I would recommend #6 solid because grounding is so important up there where it is exposed and it is expected to last 20+ years. The NEC is a minimum standard.
        This is why I rarely ever answer these questions. You do not know the difference between a Equipment Ground Conductor and a Ground Electrode Conductor. The # 10AWG EGC you are referring too is not an EGC, it is a GEC and not covered by 250.122 which is determined by the breaker size. EGC clears ground faults on circuit conductors. EGC clears high voltage from lightning and over head high voltage lines. The GEC is covered by 250.50 through 250.64, and installed in accordance with 250.60. Running it in conduit is a big No-No unless special precautions are strictly followed.
        MSEE, PE

        Comment


        • #5
          Originally posted by Sunking View Post
          This is why I rarely ever answer these questions. You do not know the difference between a Equipment Ground Conductor and a Ground Electrode Conductor. The # 10AWG EGC you are referring too is not an EGC, it is a GEC and not covered by 250.122 which is determined by the breaker size. EGC clears ground faults on circuit conductors. EGC clears high voltage from lightning and over head high voltage lines. The GEC is covered by 250.50 through 250.64, and installed in accordance with 250.60. Running it in conduit is a big No-No unless special precautions are strictly followed.
          Sunking...I respectfully disagree. The #10 EGC the OP is discussing is for equipment grounding at the array. He did point out that he was using a Sunnyboy 3800 which is a string inverter, and therefore no GEC is needed at the array, only at the inverter.

          If he said he was designing a Micro-Inverter type array, then he would need an GEC run to the Array.

          Also when you upsize portions of a circuit for voltage drop, you must upsize the equipment grounding conductor also. So just referring to the breaker size, does not allways dictate EGC sizing.

          Running the GEC in conduit is common practice in the industry, but in ferrous raceways there are certain bonding requirements.

          shortcircuit

          Comment


          • #6
            Originally posted by shortcircuit2 View Post
            Sunking...I respectfully disagree. The #10 EGC the OP is discussing is for equipment grounding at the array. He did point out that he was using a Sunnyboy 3800 which is a string inverter, and therefore no GEC is needed at the array, only at the inverter.

            Wrong all modules and racking must be bonded to the GEC

            If he said he was designing a Micro-Inverter type array, then he would need an GEC run to the Array.

            Also when you upsize portions of a circuit for voltage drop, you must upsize the equipment grounding conductor also. So just referring to the breaker size, does not allways dictate EGC sizing.

            Wrong again see 690.45 A

            Running the GEC in conduit is common practice in the industry, but in ferrous raceways there are certain bonding requirements.

            shortcircuit
            comments in red
            NABCEP certified Technical Sales Professional

            [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

            [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

            [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

            Comment


            • #7
              Naptown...what section 2011NEC regarding grounding electrode conductor to the array and modules?

              Comment


              • #8
                Originally posted by shortcircuit2 View Post
                Sunking...I respectfully disagree. The #10 EGC the OP is discussing is for equipment grounding at the array. He did point out that he was using a Sunnyboy 3800 which is a string inverter, and therefore no GEC is needed at the array, only at the inverter.
                Sorry but you are just plain wrong. It does not matter if it is string or micro-inverters. The frames of all the PV modules are bonded to a GEC. Micro-Inverters have an additional EGC which is ran with the circuit conductors in the wiring harness.
                MSEE, PE

                Comment


                • #9
                  Originally posted by shortcircuit2 View Post
                  Naptown...what section 2011NEC regarding grounding electrode conductor to the array and modules?
                  It is very clear with no doubts:

                  690.47 Grounding Electrode System.

                  (A) Alternating-Current Systems. If installing an ac system,
                  a grounding electrode system shall be provided in
                  accordance with 250.50 through 250.60. The grounding
                  electrode conductor shall be installed in accordance with
                  250.64.

                  Specifically here is the meat and potatoes.

                  (D) Additional Electrodes for Array Grounding.
                  Grounding electrodes shall be installed in accordance with
                  250.52 at the location of all ground- and pole-mounted
                  photovoltaic arrays and as close as practicable to the location
                  of roof-mounted photovoltaic arrays.

                  That has noting to do with equipment grounding conductor.
                  MSEE, PE

                  Comment


                  • #10
                    My references were to the 2011 NEC

                    690.47(D) is gone in 2011

                    Comment


                    • #11
                      Grounding

                      You're pretty much on track with you installation grounding plan. The #8 AWG grounding wire that runs from you Inverter to the Service Panel must be continuous. You need to bond it to the AC disconnect (at a grounding bar) but keep it continuous. Don't run two separate wires or the local inspector may call you out on this. This #8 AWG grounding wire can be insulated and should be terminated at the inverter at the terminal ground symbol without the circle. Please call SMA Sunnyboy tech support to confirm this. They will tell you that this conductor is called a GEC.

                      The ground wire that runs from the Array to the Inverter is an EGC and will be terminated at the Inverter on the terminal ground symbol with the circle.
                      Again, please call SMA Sunnyboy tech support to confirm this. They will tell you that this conductor is called an EGC.

                      You should always use grounding bushings where your conduit enters the Inverter, AC disconnect, and also the Service panel if you are using the concentric knockouts. Grounding in Solar is extremely important due to the higher voltage levels involved and most inspectors will really focus on grounding in an installation and sometimes ignore everything else.

                      Oh yeah - make sure that ALL of your rails and ALL of your panels are grounded bonded to each other and then to the combiner box. Your local jurisdiction may allow you to use WEEBS for the panels but check just to be sure. Inspectors will almost always check to see that your array is properly bonded.

                      Good luck on your installation!!

                      Comment


                      • #12
                        I think Connecticut is on 2005 still...

                        Comment


                        • #13
                          This thread discusses something similar: http://www.solarpanelstore.com/forum...c.php?f=5&t=15

                          Comment


                          • #14
                            All this discussion is a moot poin tuntil you know what code cycle th eOP jurisdiction is on. Very few jurisdictions have adopted 2011. I know some still on 1999.
                            MSEE, PE

                            Comment


                            • #15
                              Originally posted by Sunking View Post
                              All this discussion is a moot poin tuntil you know what code cycle th eOP jurisdiction is on. Very few jurisdictions have adopted 2011. I know some still on 1999.
                              I agree...sorry for the confussion. Here in Massachusetts we adopt the new code on the year it comes out. We haven't driven ground rods for over 2 years according to 690.47(D)...and from the early reviews of the 2014, its not coming back.

                              Comment

                              Working...
                              X