Fronius IG unit and ac side resistance

[elecsol]

Morning guy's

i am installing a Fronius IG inverter and it states that the max resistance at the ac side from inverter to main service head is max 0.5 ohms, if i have a PME system am i right in assuming the zs at inverter is the zs at board plus max 0.5 ohms for example zs at board 0.35 ohms plus ac cable max 0.5 ohms = max zs at inverter 0.85 ohms

ie max cable cable r1 r1 0.5 ohms


cheers

 

[SolarCity]

Presumably this is an IG TL inverter? I don't think it's an issue on standard IG inverters.

Are you getting confused between Zs and Ze? Zs will be the reading at the inverter.

 

[elecsol]

true zs at inverter ze is actually 0.21 and zs at cu is 0.2 zs at inverter is 0.61 so r1r2 is .41 ish

also i have been using fp cable for ac side is this over the top or a requirement, generally clipped direct, if cable clipped dirct i assume no rcd required

thanx for advice

 

[SolarCity]

Your r1 + r2 reading seems high. What cable are you using and what length?

 

[elecsol]

2 core FP 2.5mmcsa prob 30 meters

 

[SolarCity]

What inverter are you using? I reckon you should look at upgrading that cable - seems undersized to me.

 

[elecsol]

I have changed cable for 2 core and earth FP 4mm csa
system has fired up ok

cheers

 

[dansk]

If your doing r1r2 with an isolator at cu end the isolator can give you a high reading, I've found this out a few times.

 

[elecsol]

thanx for the advice i will remember that for the future installs

 

[SolarCity]

If your doing r1r2 with an isolator at cu end the isolator can give you a high reading, I've found this out a few times.

Hmm, sounds like a dodgy isolator to me....

 

[dansk]

Agreed, it was, but i sometimes swap "line" onto another pole and it they been alright - all im trying to say, is sometimes high R1+R2 tested through a closed isolater or two can be a reason for high reading.