Panels connected to micro-inverters...bonding needed?

[Zee]

Does NEC require I bond module frames if they connect to micros? Wouldn't the max V be under 48 VDC? Typical 60 cell module is 40 V.O.C ....and even in cold it is < 48 VDC.

 

[ggunn]

Does NEC require I bond module frames if they connect to micros? Wouldn't the max V be under 48 VDC? Typical 60 cell module is 40 V.O.C ....and even in cold it is < 48 VDC.

Some if not all microinverters have a ground wire in their trunk line which is bonded to the case of the inverter, which is bonded to the racking and module frames, so that ground wire is the EGC for the array.

 

[peterlarsen.suntec]

Most racking systems are UL Listed for integrated equipment grounding between module frames and racking. If you are mounting micros to module frames you must check to be sure modules are listed for frame mounting and use appropriate grounding/mounting hardware. Some racking systems include self piercing WEEB washers between module frames and rails as well as ground lugs, some use self piercing/grounding mid and end clamps. The Micro inverter mounting hardware from most racking systems are listed for integrated grounding between micros and rails. Enphase Micro inverters have internal grounding as ggunn pointed out so you are not required to connect your racking EGC to any other ground if the racking is UL Listed as self grounding and you use listed grounded mounting hardware for micros.
If you are using a rail less system (Quick Mount), specify Micro inverters and they will send the appropriate micro mounting hardware. If you are using a non integrated grounding system (DPW TPM) you will need to use self piercing washers, drop in lugs, and SS mounting hardware on module frames, rails, and posts connected together with #6 bare copper. Use grounding washers on the micros.

In any event, I still use listed drop in ground lugs, with self piercing Wiley WEEB washers and mechanical attachments (stainless steel), mounted on all rails with #6 bare copper. I use Soladeck on the roof to transition from the Engage cable and terminate the #6 bare there. This pleases the inspectors and the bare #6 is great to strap my engage cable to between rails.

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[jaggedben]

Yes, you need to bond module frames. Basic equipment bonding requirements.

DC Vmax is a little irrelevant when you've got a 240V AC trunk cable running on the array.

I'm not aware of any products where the trunk cable EGC bonds the actual module frame as opposed to merely the micro itself. Unless maybe they are AC modules.

 

[Zee]

I appreciate the answers, and the attention to detail.
I understand all that: integrated EGC in trunk cable bonds micros, and rails to micros thru mounting bolts. Modules are bonded to rail thru mid-clamps on 99% of racking. Bonding splices. Etc.


Couldn't ti be argued that ac trunk cable only runs on RACKING? Not modules. Not sure if i buy this myself..... but hear me out here.

The micros do not touch modules.

Technically, the modules don't see more than 48 VDC.
The way I see it is the mod.s are maximum 48 VDC components.... bolted to...... a bonded and grounded metal rack and micro system at 240 VAC.

Why would I not want to bond modules, especially since most mid-clamps already automatically bond modules to rails?
Because some inspectors want/demand lay-in-lugs on module frames. I am fine with bonding mid-clamps. And i will always use them. But..... Lay in lugs......not a fan, given a choice.....been there, done that 10 yrs ago:rant: :thumbsdown:

And I nearly failed inspection even though everything was bonded..... but inspector wanted lay in lugs. I could just tell inspector, "modules don't even need bonding, but look here, I did it anyways by way of the bonding mid-clamps, b/c i am a swell guy ".

 

[ggunn]

The micros do not touch modules.

They don't need to. The modules are typically bonded to the rails via WEEBs or other anodization piercing clips and the microinverters are similarly bonded to the rails. The EGC in the microinverter trunk lines bond them all back to the service GEC.

 

[jaggedben]

Or don't bond the microinverters to the rails but run a separate bare EGC from the rail to the same j-box as the trunk cable.

Either way I don't know what to say about inspectors who ask for lay-in lugs on modules, that's definitely out of date.

Voltage really doesn't matter as far as I know.