Grounding of Module Frames with transformerless inverters?

[jerriais]

Hi all,

I heard somewhere that with the new transformerless inverters from SMA and others there is a need to ground all the modules and mounting structure.

Can anyone shed any light on this?

Thanks!

 

[SolarCity]

That's right. If the inverter is transformerless then the array must be earthed.

 

[jerriais]

So that would be a lot of extra work on the roof, not sure if it's worth getting the TL inverters then, and they're more expensive than the regular Sunny Boy inverters.

 

[SolarCity]

Also, if the incomer is PME then you have other issues. I don't really see the point of transformerless inverters but I'm sure there must be some point to it.

 

[dansk]

We use these transformerless inverters with electrical seperation built in.

 

[jerriais]

It's nice that they have 2 MPPT trackers so even if one string is shaded the array can produce decent power, good for E-W roofs for example but with all the extra hassle I don't think I'll be trying them. Steca do a double tracking inverter which isn't transformerless (I think) so that might be a better bet. Thanks for the info Biggs!

 

[jerriais]

So does that letter give you official clearance to install without grounding the modules?

 

[TedM]

Is there a typo in that letter where they mention 300mA in 0.3s in the text but have 30mA at 0.3s in the table?

 

[dansk]

It gives official notification that the inverter has built in protection and therefore complies with the electrical seperation issue and RCD class B, and if your complying with that then everything else concerned with it drops into place.

 

[dansk]

So does that letter give you official clearance to install without grounding the modules?

No its just saying anything over 300ma must comply to 0.3s (thats the way i interpret it)