Microinverter Grounding Requirements - Enphase vs Power One
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NABCEP certified Technical Sales Professional
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I personally know John from working on NEC Code Panels and know the intent. But here is what the NEC says about using both the EGC and GEC as the same conductor. The conductor has to be sized to the largest conductor. In most cases that is going to be #6 AWG with 8 AWG being the smallest acceptable.
So ho win the heck are you going to do that with micro-inverters? Simple you cannot because the modular cabling sizes the EGC to a #12 or 14 AWG. That does not comply for GEC requirement. You would have to replace it with a # 8 or #6 AWG which is impossible.MSEE, PEComment
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I personally know John from working on NEC Code Panels and know the intent. But here is what the NEC says about using both the EGC and GEC as the same conductor. The conductor has to be sized to the largest conductor. In most cases that is going to be #6 AWG with 8 AWG being the smallest acceptable.
So ho win the heck are you going to do that with micro-inverters? Simple you cannot because the modular cabling sizes the EGC to a #12 or 14 AWG. That does not comply for GEC requirement. You would have to replace it with a # 8 or #6 AWG which is impossible.
I also just found this drawing. Not sure if it shows anything new though.Attached FilesComment
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OK here is the deal After this I will not respond to this thread anymore.
John took a lot of heat on this, and it needs repeated here. Exercising the combined option is asking for lightning to enter your home. If you use separate a GEC routed directly to earth bypasses your home. Well most of the fault current is diverted around your home. Combine the two and you now have a direct route (And only route) through your home wiring system to get to earth.
So is it code compliant? Yes.
Is it smart and best practice? No. Not even remotely close.MSEE, PEComment
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The sizing requirement technically only applies to the "combined conductor". It technically starts from where they are combined, correct? This would be at the point where the #10 EGC (in the trunk cable of the microinverters) and the #6 GEC combine. From there on I would have a conductor that meets this requirement.
I also just found this drawing. Not sure if it shows anything new though.
Note also on my install I'm in a very low lightning zone. IIRC, in 15 years I don't think we've had a single lightning strike in our city. Earthquakes yes, lightning not so much. Otherwise I would consider adding the supplementary GEC for lightning protection. Instead, I focused on high quality roof mounting hardware, and care taken to go well beyond code requirements for roof installation.
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SharpTComment
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Also remember that this combined GEC/EGC needs to be unspliced or irreversibly spliced all the way back to the main panel. And bonded to every metal chassis/box it goes through, and to the metal conduit, if metal is used with knockouts or terminated.
Note also on my install I'm in a very low lightning zone. IIRC, in 15 years I don't think we've had a single lightning strike in our city. Earthquakes yes, lightning not so much. Otherwise I would consider adding the supplementary GEC for lightning protection. Instead, I focused on high quality roof mounting hardware, and care taken to go well beyond code requirements for roof installation.
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SharpT
Does the combined GEC/EGC have to be insulated (green)? I was planning to use a #8 or #6 THWN-2 ground wire which I would irreversibly splice to the solid bare GEC coming into the roof J-box from the panels, inverters and racking.Comment
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Same here. In the SF Bay area where I live, lightning is very unusual - or rather, inexistent.
Does the combined GEC/EGC have to be insulated (green)? I was planning to use a #8 or #6 THWN-2 ground wire which I would irreversibly splice to the solid bare GEC coming into the roof J-box from the panels, inverters and racking.
Either green, bare, or green-yellow. I actually used a continuous uncut bare #8 wire, from the panels, inverters, rails, all the way in conduit through the AC disconnect and on to the main panel. One wire. Bonded the trunk cable EGC to it via screws in the roof junction box.
Some inspectors will require #6 for physical damage concern on the roof... I brought my inspector out before wiring to discuss on site, as I didn't want to remove/replace expensive wiring.
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SharpTComment
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RUn #8 stranded thru inverters .
Must be continuous (irrversible crimps OK).
Splitbolt on #10 EGC from harness and also from array (panell frames and rails) in rooftop J-box.
(this does not need to be irrev crimp)
You now have a combined AC EGC / DC GEC.
Run this #8 GEC/EGC, UNSPLICED, with hot wires in conduit, down to gr. bar in main.
Must land in main.
Done it 20 times in solar heavy jurisdictions.Comment
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RUn #8 stranded thru inverters .
Must be continuous (irrversible crimps OK).
Splitbolt on #10 EGC from harness and also from array (panell frames and rails) in rooftop J-box.
(this does not need to be irrev crimp)
You now have a combined AC EGC / DC GEC.
Run this #8 GEC/EGC, UNSPLICED, with hot wires in conduit, down to gr. bar in main.
Must land in main.
Done it 20 times in solar heavy jurisdictions.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
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Comment
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I personally know John from working on NEC Code Panels and know the intent. But here is what the NEC says about using both the EGC and GEC as the same conductor. The conductor has to be sized to the largest conductor. In most cases that is going to be #6 AWG with 8 AWG being the smallest acceptable.
So ho win the heck are you going to do that with micro-inverters? Simple you cannot because the modular cabling sizes the EGC to a #12 or 14 AWG. That does not comply for GEC requirement. You would have to replace it with a # 8 or #6 AWG which is impossible.
I was very confused regarding this for a while.
"VIII. DC systems"
is the heading under which the following appears. Hence any mention of conductors applies to DC system conductors. only.
per 250.166 B :
[the DC GEC]...."shall not be smaller than the largest conductor supplied by the system"
At least IMHO.Comment
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Actually...
are the POWER ONE MICROS transformerless......
And would that affect the DC GEC req.s?Comment
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Can one conductor be used to run run through inverters, panels and racking?Comment
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No reason not to as long as you can figure out a way to route it with only irreversible splices and still remove components that need replacement without too much hassle. Sometimes it is easier to run two or more separate unbroken wires.SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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