Solar Unistrut frame shocking me

[Brandan]

Hey guys

I hooked up my 11 panel string to my Growatt SPH 6000 and it is running fine but i happened to touch the aluminium ladder and then the steel frame, got a strong tingle in my hand so i got my multimeter out and read 38V AC coming from the steel frame.

I haven't grounded the array just yet but this is only happening when the inverter is using battery power and the arrays not making any power.

I'm really confused on how theres AC voltage on the solar panel frame and would really appreciate any help on this.

Many thanks

 

[SamDeleted]

I would bet it's the growatt leaking AC up the DC lines

I think appropriate grounding would solve the issue , but I'm no expert!

 

[Brandan]

I would bet it's the growatt leaking AC up the DC lines

I think appropriate grounding would solve the issue , but I'm no expert!

Yea i got people telling me that. Im surprised at how theres no DC voltage to earth day or night but im getting AC voltage

 

[AntronX]

Most likely due to solar panel capacitive coupling to frame or moisture ingress into EVA film breaking solar panel isolation barrier. Set your multimeter to AC mA range and measure leakage current at the same spot where you measured 38 Vac. Ground the array frames to solve this.

 

[Brandan]

Most likely due to solar panel capacitive coupling to frame or moisture ingress into EVA film breaking solar panel isolation barrier. Set your multimeter to AC mA range and measure leakage current at the same spot where you measured 38 Vac. Ground the array frames to solve this.

Took a reading, hardly anything in terms of amperage, voltage is still there. Suppose an earth rod will fix it. Thanks for the help.

 

[Adam De Lay]

Something like this?

 

[dmsims]

@Brandan Could you share how you built the ground mount and components used ?

 

[AntronX]

Suppose an earth rod will fix it.

It will but should be bonded to main ground rod in your house electrical service or you risk burning out your inverter during close by lightning strike induced ground currents (assuming it's a ground mount array placed a distance away from inverter). You also should have a surge arrester at the array side.

 

[ArtieKendall]

This is from the user manual for the LV6548 inverter/charger:

"WARNING: Because this inverter is non-isolated, only three types of PV modules are acceptable: single crystalline, poly crystalline with class A-rated and CIGS modules. To avoid any malfunction, do not connect any PV modules with possible current leakage to the inverter. For example, grounded PV modules will cause current leakage to the inverter. When using CIGS modules, please be sure NO grounding. "

So what is a confused newbie like me supposed to do?

 

[SamDeleted]

So what is a confused newbie like me supposed to do?

Cry lol

 

[Brandan]

Something like this?

Yea pretty much. Wasn't nothing crazy but a small tingle. Was worried it was a severe danger.

 

[Brandan]

@Brandan Could you share how you built the ground mount and components used ?

Its not a ground mount. Just unistruts on top of a pergola

 

[Adam De Lay]

Yea pretty much. Wasn't nothing crazy but a small tingle. Was worried it was a severe danger.

From my very limited understanding, I believe I read that cheaper AIO units don't have (or have very poor) isolation between the PV and AC. It's a problem in a lot of these style inverters, but the panels should be earth-grounded anyways.

 

[zanydroid]

This is from the user manual for the LV6548 inverter/charger:

"WARNING: Because this inverter is non-isolated, only three types of PV modules are acceptable: single crystalline, poly crystalline with class A-rated and CIGS modules. To avoid any malfunction, do not connect any PV modules with possible current leakage to the inverter. For example, grounded PV modules will cause current leakage to the inverter. When using CIGS modules, please be sure NO grounding. "

So what is a confused newbie like me supposed to do?

My understanding is:

I think this means not to use negative or positive grounded panels. I don’t think those are common at all nowadays unless you bought pretty old solar panels. Nowadays typical solar panels have all electrical components (bypass diodes, cells, bus wires) isolated from the frame, so ground away.

NEC requires you to bond all metal parts to ground whether with ungrounded or grounded modules. There is no way the inverter or solar panel would pass UL if the bonding blows things up.

A caveat being that with these unlisted AIOs, who the heck even knows sometimes…

EDIT: even if the components are galvanically isolated, they can still induce current across the boundary. IE isolation transformers are galvanically isolated but still induce voltage. With the shitty ad hoc transformer going on here with the AC voltage propagating into the DC lines, there should be very little current leaking into the panel, so grounding should take care of the induced voltage with no problems.

 

[zanydroid]

I'm really confused on how theres AC voltage on the solar panel frame and would really appreciate any help on this.

The voltage difference between DC+ / DC- is a "fixed" DC voltage as determined by the MPPT operating point, but that doesn't mean the voltage from DC+ / DC- to ground is also fixed. Surely there is some varying voltage happening for you, to be able to couple some voltage to the frame.

(Or you have a short, but that ought to be ruled out by your multitester testing showing that there is not much leakage current)

May want to go through and make sure every rail is bonded. Sometimes you can bond through the clamps & solar modules. You can also add more grounding lugs for backup grounding. IMO that's a good idea because it ensures that the rails are always grounded regardless of what you're doing when moving modules around.

 

[zanydroid]

Yea pretty much. Wasn't nothing crazy but a small tingle. Was worried it was a severe danger.

The induced current might cause you to fall off a ladder from surprise, other than that by itself it's probably not bad (though who knows how bad the induced current can get with these cheap AIOs).

Probably more important is that it indicates inadequate grounding, so if there is a fault capable of carrying real vs leakage DC (probably single fault can achieve this) or AC (probably multiple faults needed here) and you touch the frame, you'll have a bad day. And the ground fault protection measures (assuming the cheap AIO has it, lol) likely assumes the grounding is done correctly. Often inverters are not able to render the installation completely safe in a fault (in large part because the solar panels are going to still be at voltage unless you cover them up, and the inverter isn't able to do that ), and instead raise an alarm or stop proceeding to let you know something is F'd and needs investigation

 

[ncsolarelectric]

All bare metal parts, including the panel frames, must be Earth grounded to prevent shocks or death from ground faults. That's an NEC requirement here. If they're bolted to a wood pergola, then every panel needs a ground lug and a continuous ground wire to bond them all together, and then grounded at your main panel to Earth.