PV Array Equipment Grounding

[shortcircuit2]

Is there cause for concern and safety with the new Enphase IQ Microinverter with regard to the AC 2-wire trunk cable that has no equipment grounding conductor? Is it a Code violation? 300.3(B)(2)

These inverters will be used on Arrays in both AC Module systems and Microinverter systems.

My thoughts are that the only equipment grounding connection now will be at a single point on listed 2703 array mounting systems. One errant grounding installation and no more equipment ground on the array. Previous microinverter's had more redundant grounding through the trunk cable with 3-wires.

As industry manufacturer's compete for the low cost system advantage, I don't agree with sacrificing the importance of equipment grounding, especially on rooftops exposed to extreme weather conditions over the expected life cycle of these systems.

 

[ggunn]

Is there cause for concern and safety with the new Enphase IQ Microinverter with regard to the AC 2-wire trunk cable that has no equipment grounding conductor? Is it a Code violation? 300.3(B)(2)

These inverters will be used on Arrays in both AC Module systems and Microinverter systems.

My thoughts are that the only equipment grounding connection now will be at a single point on listed 2703 array mounting systems. One errant grounding installation and no more equipment ground on the array. Previous microinverter's had more redundant grounding through the trunk cable with 3-wires.

As industry manufacturer's compete for the low cost system advantage, I don't agree with sacrificing the importance of equipment grounding, especially on rooftops exposed to extreme weather conditions over the expected life cycle of these systems.

Certainly not if it brings back the necessity of grounding all the rails with external lugs and bare copper.

 

[pv_n00b]

The only constant is change and new ways of doing things are developed to mostly reduce costs and sometimes make installations safer. EGCs are going the way of the dodo out in the array, replaced by listed mounting systems that serve the function. Overall I think it's just as safe. I've seen too many rusty corroded grounding lugs out there.

Keep in mind that in most commercial building construction metallic conduit takes the place of the EGC, that's kind of scary considering some of the sloppy conduit connections I've seen in EMT.

 

[jaggedben]

Is there cause for concern and safety with the new Enphase IQ Microinverter with regard to the AC 2-wire trunk cable that has no equipment grounding conductor? Is it a Code violation? 300.3(B)(2)

These inverters will be used on Arrays in both AC Module systems and Microinverter systems.

My thoughts are that the only equipment grounding connection now will be at a single point on listed 2703 array mounting systems. One errant grounding installation and no more equipment ground on the array. Previous microinverter's had more redundant grounding through the trunk cable with 3-wires.

As industry manufacturer's compete for the low cost system advantage, I don't agree with sacrificing the importance of equipment grounding, especially on rooftops exposed to extreme weather conditions over the expected life cycle of these systems.

I don't see how it's any worse than systems that don't use microinverters. I never thought the trunk cable EGC bonded the racking anyway. How would it do that?

Certainly not if it brings back the necessity of grounding all the rails with external lugs and bare copper.

Since when has that not been necessary? Or are you just referring to the reduction in parts gained from clamps that provide bonding?

 

[ggunn]

I don't see how it's any worse than systems that don't use microinverters. I never thought the trunk cable EGC bonded the racking anyway. How would it do that?



Since when has that not been necessary? Or are you just referring to the reduction in parts gained from clamps that provide bonding?

It's not necessary with microinverters that provide a grounding conductor in the trunk cable. The inverters are grounded and bonded to the module frames, which are bonded to the rails. As long as the module clips are listed for it, of course.

 

[jaggedben]

It's not necessary with microinverters that provide a grounding conductor in the trunk cable. The inverters are grounded and bonded to the module frames, which are bonded to the rails. As long as the module clips are listed for it, of course.

How? With weebs? Where does Enphase say you can do that?

(BTW, the new IQ inverters also have a plastic housing, so that wouldn't work anymore.)

 

[shortcircuit2]

I don't see how it's any worse than systems that don't use microinverters.

I see it as bigger hazard in the AC system if the equipment ground is lost and the array became energized from a compromised trunk cable with the potential to ground in the AC system.

I never thought the trunk cable EGC bonded the racking anyway. How would it do that?

The previous generation of enphase inverters with 3-wire trunk cables had continuity to ground through mounting at rails thereby creating redundant grounding.

For example SM Solarmount grounding through previous generations of microinverters was accomplished as outlined below.

SM SOLARMOUNT INSTALLATION GUIDE PAGE MICROINVERTER SYSTEM GROUNDING. EQUIPMENT GROUNDING THROUGH ENPHASE MICROINVERTERS. The Enphase M215 and M250 microinverters have integrated grounding capabilities built in. In this case, the DC circuit is isolated from the AC circuit, and the AC equipment grounding conductor (EGC) is built into the Enphase Engage integrated grounding (IG) cabling. In order to ground the SOLARMOUNT racking system through the Enphase microinverter and Engage cable assembly, there must be a minimum of three PV modules connected to the same trunk cable within a continuous row.Continuous row is defined as a grouping of modules installed and bonded per the requirements of this installation guide sharing the same two rails. The microinverters are bonded to the SOLARMOUNT rail via the mounting hardware.Complete equipment grounding is achieved through the Enphase Engage cabling with integrated grounding (IG). No additional EGC grounding cables are required,as all fault current is carried to ground through the Engage cable.SOLARMOUNT INTEGRATED BONDING ADVANTAGE WITH SYSTEM GROUNDING THROUGH ENPHASE MICROINVERTERS AND TRUNK CABLES LOSE ALL THE COPPER & LUGS

 

[shortcircuit2]

Certainly not if it brings back the necessity of grounding all the rails with external lugs and bare copper.

Yes...much more labor and material grounding with all those lugs and copper. I agree.

But an installation with all those lugs and copper wire is safer IMO.

Kinda like a swimming pool...we bond everything for an assured ground-fault path with all metal parts. There is not just a single point equipment ground connection. I feel that the PV Array should have similar practice with bonding and grounding. Many PV Arrays are moving towards a single point ground connection through the 2703 listing. These systems are exposed to extreme weather conditions and the failure of the single point ground connection in the Array will introduce hazards.

 

[ggunn]

How? With weebs? Where does Enphase say you can do that?

(BTW, the new IQ inverters also have a plastic housing, so that wouldn't work anymore.)

Actually, I don't deal with Enphase much any more; most of the micros I deal with are SunPower, and yes, their equipment is UL2703 listed to provide grounding to the racking. WEEBs are old news; Sunpower's mid and end clips dig into the anodization of both the module frame and the rail it is affixed to. The microinverters come installed on the modules and are bonded to them. The trunk cables contain a grounding conductor to bond the assembly to a ground bar in a junction box where we switch from the trunk cable to THWN-2 CCC's and a #8 ground back to the service.

 

[ggunn]

Yes...much more labor and material grounding with all those lugs and copper. I agree.

But an installation with all those lugs and copper wire is safer IMO.

Kinda like a swimming pool...we bond everything for an assured ground-fault path with all metal parts. There is not just a single point equipment ground connection. I feel that the PV Array should have similar practice with bonding and grounding. Many PV Arrays are moving towards a single point ground connection through the 2703 listing. These systems are exposed to extreme weather conditions and the failure of the single point ground connection in the Array will introduce hazards.

How is that less safe than the system we used to have where we had to have one continuous serpentine unspliced ground from every piece of rail connected to the grounding electrode? It had a single point of potential failure as well.

 

[bbartmasse r]

The trunk cables contain a grounding conductor to bond the assembly to a ground bar in a junction box where we switch from the trunk cable to THWN-2 CCC's and a #8 ground back to the service.

Curious why you'd run a #8 ground in this case?

thanks

 

[shortcircuit2]

How is that less safe than the system we used to have where we had to have one continuous serpentine unspliced ground from every piece of rail connected to the grounding electrode? It had a single point of potential failure as well.

In the previous micro inverter trunk cable, the equipment ground created the redundant ground everywhere there was a inverter mounted along with the #6 rail bonding conductor. The #6 and the trunk cable ground wire would come together in the deck box, where all the grounds came together. This setup had multiple points of equipment grounding.

Now you have just 1 equipment grounding point on the array and no equipment grounding conductor in the trunk cable.

 

[jaggedben]

Now you have just 1 equipment grounding point on the array and no equipment grounding conductor in the trunk cable.

But we allow that for systems with 600V DC conductors, and have for many years. I mean, redundant bonding is surely not a bad thing but I don't think you've made the case that the bare conductor bonding to rail is not sufficient.

 

[ggunn]

In the previous micro inverter trunk cable, the equipment ground created the redundant ground everywhere there was a inverter mounted along with the #6 rail bonding conductor. The #6 and the trunk cable ground wire would come together in the deck box, where all the grounds came together. This setup had multiple points of equipment grounding.

Now you have just 1 equipment grounding point on the array and no equipment grounding conductor in the trunk cable.

I don't think you understood what I asked. In the days of grounded string inverters, the only array equipment grounding was done through that single serpentine bare copper wire. I disagree with the idea that trunk wire grounding through microinverters is less safe. In fact, most of the microinverter systems we build have more than one branch; each branch has its own grounding conductor and each microinverter has its own parallel ground connection to the array.

 

[ggunn]

I don't think you understood what I asked. In the days of grounded string inverters, the only array equipment grounding was done through that single serpentine bare copper wire. I disagree with the idea that trunk wire grounding through microinverters is less safe. In fact, most of the microinverter systems we build have more than one branch; each branch has its own grounding conductor and each microinverter has its own parallel ground connection to the array.

Sorry; someone came to talk with me and I ran out of edit time. What I meant to add is that nearly all of the time the only part of the system that has only a single grounding wire is the run from the solar load center (AC combiner) back to the service, and it's in metal conduit with grounding bushings.

 

[shortcircuit2]

I don't think you understood what I asked. In the days of grounded string inverters, the only array equipment grounding was done through that single serpentine bare copper wire. I disagree with the idea that trunk wire grounding through microinverters is less safe. In fact, most of the microinverter systems we build have more than one branch; each branch has its own grounding conductor and each microinverter has its own parallel ground connection to the array.

Yes...I think we are talking about 2 different systems. I was referring to the newer Enphase IQ Micro Inverters. They have NO EGC in the trunk cable at all.

 

[shortcircuit2]

Sorry; someone came to talk with me and I ran out of edit time. What I meant to add is that nearly all of the time the only part of the system that has only a single grounding wire is the run from the solar load center (AC combiner) back to the service, and it's in metal conduit with grounding bushings.

Yes...I understand this. This EGC is protected in the AC Combiner or a Raceway.

The single point grounding I have concern for is the equipment grounding connection to the Array on the rooftop exposed to the elements. Many of the newer UL 2703 mounting systems only call for a single EGC wire connection.


If this single point ground connection to the Array fails...

1. On a DC system, will the GF device pick up a ground fault to the metallic Array parts?

2. On an AC system, will the overcurrent device open? Or will the Array be energized in a Fault to the metallic Array parts?

 

[jaggedben]

Okay, but again, what is it that makes the single point UL 2703 racking system inadequate? You are saying you don't agree with a manufacturer's decision to cut costs, but they aren't doing anything that 600V string inverter manufacturers aren't doing. And the latter won't even remove voltage from the array if they detect a fault.

 

[shortcircuit2]

Okay, but again, what is it that makes the single point UL 2703 racking system inadequate?

The single point UL 2703 racking system design may be adequate when installed properly...but that depends on the installer's attention to following the installation instructions...including proper torque values. Far too many installers substitute a impact gun for a torque wrench. Over torque crushes the grounding points and under torque leaves loose grounding points, both of which will fail in the elements over time. IMO, a system has a better chance of staying grounded with multiple points of connection to the EGC. Improper installation of the single ground wire connection to the Array compromises the system grounding.

You are saying you don't agree with a manufacturer's decision to cut costs, but they aren't doing anything that 600V string inverter manufacturers aren't doing.

My statement was more based on the AC system design, but there is concern in the DC system also.

And the latter won't even remove voltage from the array if they detect a fault.

By latter i assume you are referring to the DC system. No, voltage won't be removed, but the inverter should shutdown and the faulted circuit will be disconnected. The owner will know there is a problem.

My input on this is just my opinion. Third party inspectional services in this area state the #1 problem with system installation is proper grounding. The 2017 Code added redundant grounding for rooftop AC equipment in 440.9, I feel it should be the same for PV Systems.

 

[ggunn]

The single point UL 2703 racking system design may be adequate when installed properly...but that depends on the installer's attention to following the installation instructions...including proper torque values. Far too many installers substitute a impact gun for a torque wrench. Over torque crushes the grounding points and under torque leaves loose grounding points, both of which will fail in the elements over time. IMO, a system has a better chance of staying grounded with multiple points of connection to the EGC. Improper installation of the single ground wire connection to the Array compromises the system grounding.



My statement was more based on the AC system design, but there is concern in the DC system also.



By latter i assume you are referring to the DC system. No, voltage won't be removed, but the inverter should shutdown and the faulted circuit will be disconnected. The owner will know there is a problem.

My input on this is just my opinion. Third party inspectional services in this area state the #1 problem with system installation is proper grounding. The 2017 Code added redundant grounding for rooftop AC equipment in 440.9, I feel it should be the same for PV Systems.

Why would grounding connections be any more prone to installation errors than any other wiring, and why would they have more impact on the safety of a PV system? Also, as I have pointed out, the microinverter systems we install already do have multiple points of connection to ground. Each microinverter has one and each microinverter branch has a separate ground path back to the AC combiner.