Fronius Transformerless Inverter

Nemo5150 · Nov 30, 2011

Hi there

Any help most appreciated

According to the operational manual for the fronius IG TL 3.6 it has an RCMU to protect against residual DC currents. so a B type RCD is not required, It then goes on to say if an external RCD is required due to local regulations then a type B 100mA RCD should be fitted.. Does this mean if it is a TT installation it must have a seperate type B RCD????

SibertSolar · Nov 30, 2011

In a nutshell, yes. Feel free to PM me if you require any assistance. Might be worth your while doing a search on here for Type-B RCDs and TL inverters too.

Andy

Nemo5150 · Nov 30, 2011

Any suggestions where to get one? I've spoken to a couple of my local wholesalers and lets just say they aren't equipped to deal with my request...

JulianC · Nov 30, 2011

If Fronius state a type B is not required 'cos the inverter has an inbuilt RCMU to deal with DC residuals, why would it need a type B for a TT installation? Surely it either needs a type B for all eventualities or it doesn't.

Nemo5150 · Nov 30, 2011

I've read it as being because TT installations require all circuits to be RCBO/RCD protected, so the connection to the grid is via a RCD making this an external RCD. I may be wrong though..

JulianC · Nov 30, 2011

It will require an RCD for a TT installation to meet disconnection times. My question is why a type B? If the inverter is incapable of feeding DC faults onto the AC side due to its construction, as it would appear to be, then a standard RCD should suffice (see last line of 712.411.3.2.1.2). If the inverter can feed DC onto the AC side in the event of a fault, then a type B RCD should be fitted at all times, not just on a TT installation. Seems contrary to what Fronius state.

Nemo5150 · Nov 30, 2011

Many thanks JC seems straight forward when you put it like that, So in that case I can use a standard Type AC RCD I don't even need to use a type A RCD?

JulianC · Nov 30, 2011

I dunno! I'd say yes, a standard type AC would do, but it seems Fronius say not. In which case, go with the manufacturer's recommendation on the basis that they know a lot more than I do. I am just curious as to why they recommend a type B if they also state that their inverter can't feed DC onto the AC side.

bumcrack · Nov 30, 2011

Where is the spiel from fronius about this? I couldn't find it online? I was looking for this myself, as I nearly ended up with a fronius TL on a job..