My SPD caused a fire hazard? what is the cause?

[yash.aungaung]

My installer installed solar systems for a home. We are a inverter sell.
At day 1 of installation, the SPD got burned. so he replaced the SPDs. Checked everything is normal. replaced the SPDs again. after 3-4 days, one of the inverter has an issue when grid is on. but it is charging by the grid without any issue when the inverter is switched off. So we told and planned to replaced the inverter the next day. but that night the distribution box got on fire. the smoke started from the SPD (which was replaced one time before). then the whole board got on fire. From that the fire plastic lava drips also caused fire to the battery below too. the inverter on the other hand was working until the parallel cable from inverter got burned. and the battery burnt. we tested if it could be the inverter fault but to our surprise the inverter was doing okay. and the PV reverse voltage from the inverter when PV is not connected is about 40VDC.
So my question is what cause the SPD to burn? the installer said it is the inverter that caused the SPD to catch fire.? I says there might be some irregular spike voltage caused the SPD to burn but since there's no one around, the whole thing catch on fire.
I checked with another installer to see if the wiring was right. He said the way he connected to inverter PV in is wrong which is PV---->SPD----->Fuse----->Breaker----->Inverter PV in (First Pic)

Can the inverter caused the SPD to burn or is the site have some sort of irregular voltage or connection wires?
He keeps insisting the inverter caused the spd burn but that doesn't makes sense to me.
I am attaching the way he installed the PV distribution box. He does the same for all sites. there was never an issue. but this is the first time as well.

 

[yash.aungaung]

I have the video link the burning starting too. luckily the CCTV was installed there. if anyone can help me figure out, i can share the link here. this is driving me and the installer nuts.

 

[yash.aungaung]

here is the link:: https://drive.google.com/drive/folders/1Z3pNGzlIu2OSmJKw6tuVXA6uj3tqkxxI?usp=share_link

 

[MurphyGuy]

Looks like the problem originated in China.

 

[meetyg]

Yes, the wiring of the SPD is wrong!
The PV SPD should be last in the "chain", not first. It should be AFTER the fuses and breakers, because if a PV surge is to happen, it will connect either positive or negative to ground. This in effect is a short, which should cause either the fuse or breaker to open, protecting the SPD and the equipment.

You still need to understand why you are getting these surges, though.
What kind of inverter is this? What's the max Voc of the MPPT input on the inverter?
Please check for AC voltage on the PV side (yes, AC). Some inverters with high PV voltage input might have AC voltage on the PV side.

Also, make sure ALL your PV connections are solid. Sometimes if a connection is not good, it could cause arcing, which can cause voltage spikes too.

 

[yash.aungaung]

F

Yes, the wiring of the SPD is wrong!
The PV SPD should be last in the "chain", not first. It should be AFTER the fuses and breakers, because if a PV surge is to happen, it will connect either positive or negative to ground. This in effect is a short, which should cause either the fuse or breaker to open, protecting the SPD and the equipment.

You still need to understand why you are getting these surges, though.
What kind of inverter is this? What's the max Voc of the MPPT input on the inverter?
Please check for AC voltage on the PV side (yes, AC). Some inverters with high PV voltage input might have AC voltage on the PV side.

Also, make sure ALL your PV connections are solid. Sometimes if a connection is not good, it could cause arcing, which can cause voltage spikes too

The inverter is Off Grid inverter. The Voc of it is about 500Vdc. After the dissembling, We checked one of the inverter has 40vdc reverse output on PV side. The another inverter which was near the fire got soft start failed error which may have caused by the fire.
The installer has said he checked the PV voltage too. He said it is okay. But the SPD got the damaged before. He replaced it one time.
But this time happened the same issue when there’s no PV voltage (as it is 2:30am in the morning and there’s no PV voltage). I am not sure what are causing these surges. He is blaming on the inverter but if it’s the inverter fault, based on the way he did wiring, the fuse and breaker should be blown right? As the fuse and breakers are usually 400-500Vdc rated. But in the video it’s the SPD.

 

[Bud Martin]

Can you provide the link to that combiner box that has burnt SPD?
What is the rating/spec of that SPD?
The combiner has two SPD's, is the one on the right, did not burn, also connected to the panels that has the same 500 Voc as the one on the left SPD that burnt?

 

[WindWizard]

The only reason that I can think of a SPF getting hot enough to catch fire is if the voltage is exceeded or the SPF may be polarity sensitive. I doubt that two SPF's could be defective. The first time that it happened it would have been prudent to measure the voltage on the SPF and compare it to the specs of the SPF and see how close the tolerance is and polarity. The first time it got hot was a warning and it was ignored. It kind of reminds me of some of the technicians that I worked with. They kept replacing the same part without really doing the detective work that is necessary. Why did the SPF smoke in the first place? That question was never answered but it was assumed that the SPF was defective. That is called throwing parts at the problem without really discovering the root cause. If the Inverter is defective and it is exceeding the tolerance of the SPF then there may be issues with the Inverter. Myself I am not at all impressed with any SPF that catches fire., and if I know what model they are I would avoid them because I do not want my house to burn down.

 

[OffGridForGood]

What kind of inverter is this? What's the max Voc of the MPPT input on the inverter?

Zoom in on the photo - it is a POWMR unit, appears to be the 5kW model, as best I can tell from the photo.
From online specs, max PV VOC would be 500vDC They show 120 - 450 vDC recommended range.

 

[KITROBASKIN]

So sorry this happened to you.. glad you are safe.

 

[yash.aungaung]

Can you provide the link to that combiner box that has burnt SPD?
What is the rating/spec of that SPD?
The combiner has two SPD's, is the one on the right, did not burn, also connected to the panels that has the same 500 Voc as the one on the left SPD that burnt?

This is the DC SPD he used. To be honest I think the SPD is not the problem. The problem is in the ground wiring or something. He said he did the grounding to the panels frame, Dc SPD earth, AC SPD earth together and put them in the ground. And only DC SPD burnt the first time too. The AC SPD are fine. Is this correct method? and I also I saw some video that two earth rods nearby can cause voltages to pass through the grounded device.

 

[yash.aungaung]

Zoom in on the photo - it is a POWMR unit, appears to be the 5kW model, as best I can tell from the photo.
From online specs, max PV VOC would be 500vDC They show 120 - 450 vDC recommended range

Yes it is. It’s the parallel version. Solar Voltage for each inverter is about 300VDC which is well within the range.

 

[WindWizard]

This is the DC SPD he used. To be honest I think the SPD is not the problem. The problem is in the ground wiring or something. He said he did the grounding to the panels frame, Dc SPD earth, AC SPD earth together and put them in the ground. And only DC SPD burnt the first time too. The AC SPD are fine. Is this correct method? and I also I saw some video that two earth rods nearby can cause voltages to pass through the grounded device.

That is a potential possibility. The only way to check would have been when the smoke came out of the SPD then to meter the inputs and also meter the inputs to supposed ground. If the AC ground is injecting some noise then it could cause the SPD to fail. The only way would be to test with a voltmeter set on AC and DC or a scope and do some Detective work to see what was going on. I don't think the issue was the SPD but I think that the SPD smoking the first time showed that there was a problem that needed to be addressed.

 

[Bud Martin]

This is the DC SPD he used. To be honest I think the SPD is not the problem. The problem is in the ground wiring or something. He said he did the grounding to the panels frame, Dc SPD earth, AC SPD earth together and put them in the ground. And only DC SPD burnt the first time too. The AC SPD are fine. Is this correct method? and I also I saw some video that two earth rods nearby can cause voltages to pass through the grounded device.

But in your combiner box you have two exact same SPD for each set of the panel, but only the one the left burn up as shown in the video, the right one did not burn up, correct?

 

[yash.aungaung]

But in your combiner box you have two exact same SPD for each set of the panel, but only the one the left burn up as shown in the video, the right one did not burn up, correct?
View attachment 126235

the first time both got burnt. But at night the right one catches fire first. so we are not able to determine if the left also damaged too. we can only say that the right one caught fire first.

 

[yash.aungaung]

My main question is can the inverter cause this? The installer is theorizing that the PV in from inverter is releasing AC voltage or high dc voltage over the rated SPD limit.

 

[meetyg]

My main question is can the inverter cause this? The installer is theorizing that the PV in from inverter is releasing AC voltage or high dc voltage over the rated SPD limit.

Well, maybe...
See this post on an Australian forum:

PIP-5048GE/GK/MG/MGX/MAX inverters (with unsafe SCC) - AEVA Forums

Although they talk about MPP inverters, the PowrMr could be a clone (having the same unsafe design).

But they seem to be unsafe only if PV have a ground fault.

As for ground, you mentioned having two ground rods? That's not good...

At the nights that the fire occurred, did you have any lightening outside? Maybe rain?

 

[Bud Martin]

I sure like to get the full spec of this SPD, it is claiming Uc of 1000V which is pretty high, I wonder if that 1000V rating is real.
For example: https://prosurge.com/wp-content/uploads/2022/12/PVB12.5-2poles-PV-SPD.pdf
Inside these SPD are MOV.
The way it was slowly getting hot does not seem to be caused by surge, and you said it happen at night so no way the panels can supply Voltage or current that can cause the MOV to conduct for that long period of time as shown in the video to keep the MOV hot enough to start a fire, the source of that power is coming from some where, and inverter has to put out more than 1000V to exceed the Uc rating.
As other had said, it is not properly installed.
I wish I have one to test, I have hi-pot tester.

 

[Hedges]

Probably, excessive voltage (AC or DC) is being applied continuously, not something like a lightning related surge.

First, with AC and DC connections to inverter switched off (so it isn't exposed to over-voltage damage), voltages across each SPD should be checked. Needs to be within their operating voltage, well below clamping voltage. I've seen MOV that trigger at 760 VRMS (1075 V peak) used for 600Voc max inverter:

Testing Metal-Oxide Varistors (MOV)

Surge arrestors are used on AC and DC side of PV inverters for protection, to clamp high voltage transients. One inverter I have (actually several) are in the SMA family SUNNY BOY 5000-US / 6000-US / 7000-US / 8000-US. These come with a kit of MOV to protect the DC side: The MOVs are about...

diysolarforum.com

There may be AC riding on DC. Transformerless inverters do this.
3-phase circuits carry a variety of voltages, especially if high-leg or corner grounded.
A non-grounded utility connection could be shifted above ground.

If there are SPD line-to-line, and line-to-ground, each is subjected to different voltages.

I've seen SPD in a power strip burn because an ope-circuit neutral delivered 208V instead of 120V.

There are SPD available which go open on failure rather than burning. A MOV can fail shorted, then would overheat. Some area available with a thermal fuse in-line. Midnight sells packaged SPD based on those, with LED indicators for "working" and "failed"

SPD like MOV can take a huge current, but only for a very brief time. Steady applied voltage will overstress them.

 

[yash.aungaung]

Well, maybe...
See this post on an Australian forum:

PIP-5048GE/GK/MG/MGX/MAX inverters (with unsafe SCC) - AEVA Forums

Although they talk about MPP inverters, the PowrMr could be a clone (having the same unsafe design).

But they seem to be unsafe only if PV have a ground fault.

As for ground, you mentioned having two ground rods? That's not good...

At the nights that the fire occurred, did you have any lightening outside? Maybe rain?

yes Powmr is cloned designs from voltronic which I think makes for MPP as well. Most inverters we used here basically use same designs. The fire occurred at night. There’s no rain or lightning.
As for the 2 ground rods I have to confirm back. Most home has lightning rod installed. The installer said he put a new additional separate lighting rod for the solar system.