Risks of using cracked/shattered solar panel in series-parallel with other panels?

[Norwasian]

I intend to replace a panel in which a neighbor's stray slingshot round shattered the glass. It still works at present, despite the damage. However, we are currently in dry season and, so far as I am aware, it has not been rained on since the incident. What are the potential risks of procrastination in swapping out the panel? (I don't have a new one in hand yet to do this, and I'm not sure how urgent it might be.)

The panel is in a 2s2p string, VOC of about 49.8v per panel, with no fuses intervening between panels within the string. All the other panels are like new, less than a year in service. Will any of them be damaged if rain enters the cracked panel? Would the connected charge controller be harmed? Would it just spend its electrical harvest in splitting the hydrogen and oxygen atoms of the rainwater apart? (Nearby smokers beware!)

If anything in the system besides the cracked panel itself stands to be potentially damaged, would it be better to just disconnect it from the string and run on half the string's potential with the two in series that are still good?

I've tried searching the forums here but found only people attempting to make repairs (not my interest at this point) to their panels in order to keep using them. I found no one complaining of any adverse effects to their system, other than loss of PV efficiency with the damaged and/or repaired panel--but it seems in many of those cases the panels may not have been connected the way mine are, and I am still left with questions. I understand that water could cause a short circuit; I just can't seem to wrap my head around what the repercussions of such might be for a solar panel in a string with other panels.

 

[timselectric]

Water intrusion will only damage the cracked panel.
But there is a electrical hazzard, when wet. Especially if the panel frame is not properly grounded.

 

[Norwasian]

Water intrusion will only damage the cracked panel.
But there is a electrical hazzard, when wet. Especially if the panel frame is not properly grounded.

So the damaged panel will not cause problems with anything else in that string, other than reducing the output? Will the parallel string and/or the other panel in series be losing current through the damaged panel? How would grounding be involved?

I can imagine current being shorted through the damaged panel such that it has no output. I cannot imagine what the other panels' relationship to the short would be, nor how grounding would come into play.

FWIW, the frames of the solar panels are all connected to the SCCs and inverter via a ground bond.

 

[timselectric]

So the damaged panel will not cause problems with anything else in that string, other than reducing the output?

Correct

Will the parallel string and/or the other panel in series be losing current through the damaged panel?

In series current could be reduced.
In parallel voltage could be reduced.
Either way, output will be reduced.

How would grounding be involved?

Leakage to the frames (through the moisture) can be a shock hazzard.
Grounding removes the hazzard.

 

[EPicTony]

You can fix it with this for $30. Lay flat and level then apply. No more water intrusion. Seals the cracks which hides a lot of them. Kind of like repairing a windshield with superglue.

 

[Norwasian]

Leakage to the frames (through the moisture) can be a shock hazzard.

Why would the electricity go to the frames? The electricity is produced by the solar cell. It returns to the solar cell. The solar cell is basically an ion pump that forces electrons to move in one direction along a closed circuit. The frame has no reason to be in that circuit if the solar cell is shorted across itself. But even if the frame becomes part of the short, what danger does it present?

This "leakage" concept, as if electricity has a mind of its own to go out of bounds of its circuit, is one that is well refuted in the video that Will has recommended. Unfortunately, it was the standard understanding for a long time, and many still adhere to it, despite it going against the actual physics of electricity/electrical circuits.

If the frame is electrified by water intrusion, it would seem that the frame itself would be the short in the circuit, conducting the electricity produced by the panel back to itself. Touching the frame would pose no hazard in such a case--no more than placing one's hand on a terminal of a car's battery while the engine is in operation and the battery is in use. The car's rubber tires insulate it from ground. The battery is not "grounded" (earthed). Standing on the ground and touching the battery terminal is not dangerous. If electricity passes through the car's frame, and back to the battery, it has no effect on the person touching the terminal or the frame. If I'm wrong in these assessments, I'm open to enlightenment of a form which explains the reasoning with factual support.

 

[timselectric]

Why would the electricity go to the frames? The electricity is produced by the solar cell. It returns to the solar cell. The solar cell is basically an ion pump that forces electrons to move in one direction along a closed circuit. The frame has no reason to be in that circuit if the solar cell is shorted across itself. But even if the frame becomes part of the short, what danger does it present?

This "leakage" concept, as if electricity has a mind of its own to go out of bounds of its circuit, is one that is well refuted in the video that Will has recommended. Unfortunately, it was the standard understanding for a long time, and many still adhere to it, despite it going against the actual physics of electricity/electrical circuits.

If the frame is electrified by water intrusion, it would seem that the frame itself would be the short in the circuit, conducting the electricity produced by the panel back to itself. Touching the frame would pose no hazard in such a case--no more than placing one's hand on a terminal of a car's battery while the engine is in operation and the battery is in use. The car's rubber tires insulate it from ground. The battery is not "grounded" (earthed). Standing on the ground and touching the battery terminal is not dangerous. If electricity passes through the car's frame, and back to the battery, it has no effect on the person touching the terminal or the frame. If I'm wrong in these assessments, I'm open to enlightenment of a form which explains the reasoning with factual support.

It has nothing to do with the DC produced by the solar panels.
It's the AC from the inverter, on the PV circuit. Most (all high frequency) inverters do not fully isolate the AC side from the DC side. The reason for grounding anything is to protect against the shock hazzard of the AC system.

 

[Norwasian]

It has nothing to do with the DC produced by the solar panels.
It's the AC from the inverter, on the PV circuit. Most (all high frequency) inverters do not fully isolate the AC side from the DC side. The reason for grounding anything is to protect against the shock hazzard of the AC system.

I've never heard of this problem before. Can you point me to where I might find more information about this? Also, you specify the AC problem is from HF inverters. Does this mean LF inverters do not have this issue?

FWIW, my inverter is a toroidal LF inverter. So if LF inverters are exempt, I should be safe, right?

I'm also wondering if the ground bond (equipment ground) between the solar panels and the inverter would be contraindicated in such a case, as it seems to me that without it, there should be no reason for AC current to reach the panels.

 

[timselectric]

I've never heard of this problem before. Can you point me to where I might find more information about this?

Lots of threads about it in the forum.
And Will even done a video about it.

Also, you specify the AC problem is from HF inverters. Does this mean LF inverters do not have this issue?

Not limited to just high frequency inverters.
You can test your own to see. Use AC meter to check from positive and negative to ground.

FWIW, my inverter is a toroidal LF inverter. So if LF inverters are exempt, I should be safe, right?

Not exempt. Just not a guarantee, either way.

I'm also wondering if the ground bond (equipment ground) between the solar panels and the inverter would be contraindicated in such a case, as it seems to me that without it, there should be no reason for AC current to reach the panels.

It's still a hazzard to be protected against.
A fault in the inverter can electrify the PV circuit.
But on non isolated inverters, the AC is present in normal operation.

 

[timselectric]

Found the video

 

[Norwasian]

Found the video

So, it really is contraindicated to ground-bond the solar array with the inverter when using an all-in-one inverter. Wow. I hadn't seen that video, thank you. Key screen grab from it--and it was interesting to hear Will's rule #2 against grounding the all-in-one based on this:



I guess I need to disconnect the ground-bond wire next time I'm up there. And here I thought I was doing the right thing by having it there--a nice thick wire, too.

The more I learn about problems with grounding, the more wary I am of it. There are more times than many people realize where it is best to NOT ground.

 

[PVGeezer]

The module frames and support structure must be grounded. The PV source circuit conductors should not be. Do not remove the frame ground bond if thats what you're considering.

I don't think you are planning to try to continue to use the broken module but just in case you are, don't. It is junk. It cannot be repaired. If the glass is broken the cells are also guaranteed to be broken. They are very thin and tightly adhered to the glass. The cells can continue to operate even when broken, sort of, and for awhile.

But the glass is the insulating material keeping the PV circuit from being faulted to the frames and structure. If it's broken then the insulation is compromised. Best to disconnect the broken module from the circuit till you can get rid of it. Put some dielctric grease in the exposed mc connectors on the good modules so they don't corrode while you're waiting to install your new module.

 

[timselectric]

So, it really is contraindicated to ground-bond the solar array with the inverter when using an all-in-one inverter. Wow. I hadn't seen that video, thank you. Key screen grab from it--and it was interesting to hear Will's rule #2 against grounding the all-in-one based on this:

View attachment 267861

I guess I need to disconnect the ground-bond wire next time I'm up there. And here I thought I was doing the right thing by having it there--a nice thick wire, too.

The more I learn about problems with grounding, the more wary I am of it. There are more times than many people realize where it is best to NOT ground.

Absolutely not.
You are misunderstanding this.
The metal frames must be grounded.
But never ground/bond the PV circuit conductors (positive or negative)

 

[Norwasian]

Absolutely not.
You are misunderstanding this.
The metal frames must be grounded.
But never ground/bond the PV circuit conductors (positive or negative)

According to how I understood Will's video, what you're saying does not make sense. Will is stating that some solar panels he's discovered have grounded to their frames. If what you're saying is true, using a ground bond to that frame will necessarily ALSO ground "the PV circuit conductors" of said solar panels. This leaves one with the contradiction between "must be grounded" and "never ground/bond the PV circuit conductors." One cannot satisfy both requirements in the case that the panel itself is grounded to its frame. The best I option I see, in such a case (which would appear to include my shattered panel), would be to remove that ground bond.

Am I missing something?

Will has indicated that some solar panels may be faulty. Check his video starting at the 3:43 time mark. He concludes based on this that the solar panel array should not be grounded. If he's talking about the "array," he's not talking about a single panel. I ground-bonded my array--the entire support system which attaches to the frame of each panel (which is all contiguous--welded together). That is what I hear Will saying I should not be doing. If you interpret his words differently, I'd be interested in how you think he is meaning to apply this rule.

 

[PVGeezer]

Im not going to go back to look at that video because it doesn't matter. If a PV module's internal circuit is grounded to it's frame its faulty and needs to be replaced. Code requires module frames and support structures to be bonded to ground. Period.

The US PV industry used to also ground one of the PV circuit conductors, making it a neutral like in AC circuits. We later found out that was a bad idea because then if you get a fault in the array you have current flow through the short, back through the ground path to the neutral connection, then back into the circuit. And unlike AC circuits where there is a plenty of fault current available, PV circuits are current limited so fuses don't blow and circuit breakers don't trip. So the fault current would just flow continuously all day every day until it either started a fire or someone disconnected the faulty modules.

It was at that point that we learned that it was much safer to leave the PV circuits ungrounded and provide the inverters with ground fault detection. This is the way almost all of them are done nowadays.

But again, none of this changes the absolute need, for safety as well as code compliance, to bond your module and structure framing.

 

[ricardocello]

Post in thread 'I got a small electrical shock when grounding solar panels. Why?'

Sep 4, 2023

Trust me… it’s not just you that has been surprised by that shock…

• Adam De Lay

• 

 

[Norwasian]

Im not going to go back to look at that video because it doesn't matter. If a PV module's internal circuit is grounded to it's frame its faulty and needs to be replaced. Code requires module frames and support structures to be bonded to ground. Period.

The US PV industry used to also ground one of the PV circuit conductors, making it a neutral like in AC circuits. We later found out that was a bad idea because then if you get a fault in the array you have current flow through the short, back through the ground path to the neutral connection, then back into the circuit. And unlike AC circuits where there is a plenty of fault current available, PV circuits are current limited so fuses don't blow and circuit breakers don't trip. So the fault current would just flow continuously all day every day until it either started a fire or someone disconnected the faulty modules.

It was at that point that we learned that it was much safer to leave the PV circuits ungrounded and provide the inverters with ground fault detection. This is the way almost all of them are done nowadays.

But again, none of this changes the absolute need, for safety as well as code compliance, to bond your module and structure framing.

I think it does matter. And I think it's because you think it matters that you have said so much about it. The video by Mike Holtz, recommended years ago by Will Prowse, explains in detail some of the reasons that the NEC codes pertaining to grounding have recently changed. Many electricians still follow the old way, not understanding why it is faulty. My own life experiences have educated me, as I once was indoctrinated with the older theories as well.

 

[timselectric]

Am I missing something?

Yes
Metal PV frames must be grounded.
The PV circuit can not be grounded.
You are confusing the two.

 

[Norwasian]

Yes
Metal PV frames must be grounded.
The PV circuit can not be grounded.
You are confusing the two.

I think you misunderstood my post. The PV circuit of a panel can be grounded to its frame (Will used the term "leaky" for such a solar panel) when faulty or damaged. In the case that the panel is electrically connected with its frame, and that frame is grounded, it necessarily follows that the PV circuit is also grounded. This would be highly likely to apply to my shattered panel, especially if it gets wet.

 

[timselectric]

I think it does matter. And I think it's because you think it matters that you have said so much about it. The video by Mike Holtz, recommended years ago by Will Prowse, explains in detail some of the reasons that the NEC codes pertaining to grounding have recently changed. Many electricians still follow the old way, not understanding why it is faulty. My own life experiences have educated me, as I once was indoctrinated with the older theories as well.

You are either misunderstanding the information, or twisting it to your narrative.
I believe that we have been down this road before, with you.
Grounding is for personal safety. If you choose to ignore that, it's completely up to you. (As long as it only affects you)
But please don't come here and try to convince others to act in an unsafe manner.

I think you misunderstood my post. The PV circuit of a panel can be grounded to its frame (Will used the term "leaky" for such a solar panel) when faulty or damaged. In the case that the panel is electrically connected with its frame, and that frame is grounded, it necessarily follows that the PV circuit is also grounded. This would be highly likely to apply to my shattered panel, especially if it gets wet.

Correct, that's a fault condition. Which is why the frames are grounded.
This fault will cause the AC breaker or fuse to open the circuit and make it safe.

 

[ricardocello]

I think you misunderstood my post. The PV circuit of a panel can be grounded to its frame (Will used the term "leaky" for such a solar panel) when faulty or damaged. In the case that the panel is electrically connected with its frame, and that frame is grounded, it necessarily follows that the PV circuit is also grounded. This would be highly likely to apply to my shattered panel, especially if it gets wet.

Given a cracked panel, there are four DC electrical outcomes if the PV frames are properly grounded:

(1) No change, the grounded frame, PV+, and PV- are independent.
(2) PV+ is shorted to the grounded frame. This is detectable with a GFPD device.
(3) PV- is shorted to the grounded frame.
(4) PV+ and PV- are shorted together. Less or no PV power for you. Same if everything shorted together.

The resistance of the short will play a role in the performance of the panel.

 

[Norwasian]

Correct, that's a fault condition. Which is why the frames are grounded.
This fault will cause the AC breaker or fuse to open the circuit and make it safe.

In my inverter setup, there is no possibility of this. On the DC side, which includes the PV panels of course, there are no AC breakers. The only AC breaker is that which leads away from the inverter to the load side.

Will's video addresses AC passing from the inverter, through the ground bond which is common to either the positive or the negative (obviously not both at the same time, but depends on the inverter model which one it would be), and feeding back to the panels (he specifies the MPPT) via the equipment ground (ground bond). There is no AC breaker on that side of things. Nor would the DC breakers designed to protect the PV side be likely to trip on this AC fault.

 

[PVGeezer]

Where in Mike Holt's video is he saying not to bond the module frames and support structure to earth?

I think nowhere. Neither is Will. Will is saying not to ground the pv negative. Mike is not saying either to do that or not to do that. Because both grounded and ungrounded circuits are in general allowed by the NEC. I am saying that its been found that grounding PV source circuits has caused more problems than not. Most inverter manufacturers do not allow the PV source circuit conductors to be grounded.

No one is saying not to bond the module frames and support structure.

 

[Norwasian]

No one is saying not to bond the module frames and support structure.

But that's what I'm hearing @timselectric saying given the premise that the panel is damaged and thereby grounding the PV circuit to its frame. If, and perhaps only if, one is dealing with a shattered/damaged/faulty panel, that ground bond becomes unsafe.

Granted, some may choose to see the panel itself as being the unsafe component. But if it can still produce electricity, and can be made safer by eliminating the ground bond, some may prefer to do just that--at least until said panel can be replaced, as is my situation.

I'm still trying to understand, however, how that ground bond could possibly be effective in conducting AC current and opening an AC circuit when it is prepared strictly for the DC side of the system.

 

[timselectric]

But that's what I'm hearing @timselectric saying

I can't imagine how.
Because it's definitely obvious that I am not saying that.
We have been very clear in what we are saying. Yet, you're still not getting it.
I'm beginning to wonder if you are genuinely misunderstanding the information provided. Or if you are just trolling the forum..