Fronius IG Plus Inverters

Stevesolargill · Jan 31, 2012

Hi all.

Just a quick query really to see if anyone knows if these inverters have anti-DC back-feed facilities built in thus doing away with the need for a DC sensitive type B RCD to be installed??

Any help would be greatly appreciated!!

Thanks in advance.

dansk · Jan 31, 2012

Yes according to Fronious

Edit: I thought the "plus" version had an isolating tranni.

Yes they are transformer units, so DC cannot inject AC

Stevesolargill · Jan 31, 2012

dansk said:
Yes according to Fronious

Edit: I thought the "plus" version had an isolating tranni.

Yes they are transformer units, so DC cannot inject AC

Thanks for the response. SMA HF inverters have HF Transformers but still require RCDs as they have no facility to stop the back-flow of DC???

dansk · Jan 31, 2012

Not sure i understand what you mean "flow back" but IG Plus have Galvanic Isolation - therefore AC and DC are separate and DC cannot inject AC - unless im missing the point?

And hence no type B rqd

BruceB · Jan 31, 2012

Stevesolargill said:
Thanks for the response. SMA HF inverters have HF Transformers but still require RCDs as they have no facility to stop the back-flow of DC???

The clue is in the word 'transformer'. The HF series are considered galvanically isolated as far as I understand. No rcd required, let alone a type b rcd.

Stevesolargill · Jan 31, 2012

BruceB said:
The clue is in the word 'transformer'. The HF series are considered galvanically isolated as far as I understand. No rcd required, let alone a type b rcd.

If you refer to SMA's guidance note on the installation of RCD's with their inverters, you'll note that all their HF versions require a type B RCD even though they have a transformer......?

BruceB · Jan 31, 2012

That is a good point and I remember trying to square that circle many months ago in my own mind as it is a bit confusing or contradictory compared to their other statements.

Read it carefully and it says the VDE standard (which of course we do not work to here, we use 7671) requires the rcd type b, but it goes on to say that the TLs listed and all transformered inverters (I take that to include HF transformers) are exempt by virtue of their design.

On their main website they then have this page:

[ElectriciansForums.net] Fronius IG Plus Inverters

where it clearly states the HF inverters are galvanically isolated.

So in my own mind that is how I have come to consider them - galvanically isolated - and I put the confusion down to garbled German translation.

Regards
Bruce