RISO

[Ervin R Dilly]

Getting a Riso low reading and cannot find out what that means.Have checked all my input?output power and they all check.Goes to green and tries to boot up ,but then to red with the Riso low.Cant find this in the manual.Need help,thanks

[Sean Moore]

https://redelectrical.co.uk/isolation-insulation-resistance-riso-fault/

[Rob Beckers]

Ervin, is this for a solar PV inverter?
There's a trick to finding the location: When you disconnect the DC input to the inverter (depending on the type of inverter you can often do this just by switching the DC disconnect switch off), measure the Voltage between the PV positive from the panels and ground, and the PV negative and ground. The Voltage tells you how many panels "down the line" the connection to ground is located.

Each panel is around 36 - 38 Volt open-circuit (for 60-cell panels, the most common type), so if you measure 380 Volt it means your problem is 10 panels down the line.

That's how we've found the few cases of ground faults. It can be something inconspicuous, two cases was a PV wire caught between the rail and the panel. Even though the insulation looked unbroken it did set off a ground fault.

-RoB-

[Ervin R Dilly]

Thanks for the reply,It is a PVI-4.2-OUTD-S-US inverter.If I understand this right,I should be looking for a ground problem.Live on the east coast and we had wind and rain in excess of 50 MPH,so this might of done something.Thanks ,will look at it today.

[Ervin R Dilly]

So today I replaced or checked all the earth grounds and checked each cluster of panels leading into the inverter.All were reading close to 380 and the same reading at the inverter.Is it possible that I have a bad panel that got moisture in it.Or is it the inverter,which this is the 2nd in 12 years.Will try the other thing you mentioned RobHate to have such a long post,here is something else that I did,checked the #1 input with the + and the box as a grnd,got a reading,tried the +2 and nothng,hope this helps,sorry for talking so long.

[Rob Beckers]

Ervin, I can't really make anything from what you wrote. What's needed is:


Switch off the DC disconnect on the inverter.
Measure positive of input 1 vs. ground (how many Volt?).
Measure negative of input 1 vs. Ground (Voltage?).
Repeat for input 2.


I should add this only works (reliably) with a digital multimeter. You need it to be set for DC of course, panels produce DC Voltage (not AC). What you're measuring is from the terminals where the DC lines from the panels come into the inverter vs. any ground point on the inverter (housing, ground lug etc.). It doesn't have to be sunny, but it should at least be light outside. Panels don't produce a stable Voltage at night.

-RoB-

[Ervin R Dilly]

Thanks Rob,will do what you said and get back to you,dont want to buy a neww one if I dont have to.

[Ervin R Dilly]

Morning Rob,Hope I did what you wanted,here goes.String #1plus to unit grnd=908V. string #1 solar grnd to unit grnd 000.#2 string,plus to unit grnd 000, solar grnd to unit grnd 000. Hope this makes sence to you. Am I supposed to get power on the first test?Thanks again.

[Rob Beckers]

Hi Ervin,

Sounds like your short to ground is right at the negative PV wire coming from the array on input #1. Could be anywhere from the inverter connection to the first panel.

It is also entirely possible that you're doing something wrong (still) in measuring: You should never see a value above 600 Volt. That's the limit of both the inverter and residential electrical code. In practice, accounting for the rise in Voltage when it's cold outside, it's rare to see more than about 500 Volt. So a value of 900+ Volt doesn't really add up.

Maybe it's time to get someone in that knows solar PV and have them sort it out?

-RoB-

[Ervin R Dilly]

Rob,hate to keep bothering you but.Went out to the solar panel (ground mounted)and disconnected the + &- side of the main line going to the inverter Getting 90 V there and tried the earth ground,no reading there,checked the solar- and earth grnd,nothing.Went to the inverter while it was disconected and used the ohm meter again and got no reading there,so this is telling me my wire to the inverter is good.also when I sent you my readings yesterday,forgot to put in the Decimal point.So 90.8 was the reading.Looks like I may have a bad inverter,looked at the Fronius and sonny boy.Any recomendations?Thanks for bearing with me.

[Rob Beckers]

Ervin, 90 Volt between positive/negative of the entire solar string seems low. That's less than 3 panels (depending on temperature they're around 36 Volt each for 60-cell panels). The Aurora inverters needed about 150 Volt while working, and that's the lower bound. So this too doesn't quite add up...

Your ground fault could be the inverter, though if it's not, replacing it won't solve your problem. In the inverter I've only seen one particular part cause ground faults: The inputs of the Aurora inverters are all protected with MOV's, those are surge arrestors. They look like blue or red disks with 3 wires, and in the Power-One inverters are mounted in sockets so they can be removed/replaced. You can see them when you take off the upper wiring cover.

The way those MOV's fail tends to be either as a short or leaking-to-ground, setting off ground faults. They can be removed (they're only surge arrestors, they are not needed to make the inverter work), and if that results in the ground fault going away you found the cause. In your case it doesn't really sound like you're versed in electronics/electrical so this may be best left to someone who is more familiar with it.

-RoB-

[Ervin R Dilly]

Thanks rob,and you are correct on my readings.I was using to high of a scale on my MM.Today I am reading 403 on#1 and 430 on#2.Things bother me if I cant find it so today I disconnected all 10 of my panels at a time and read each one.They all were in the 38V range,Also rechecked the wire from the solar to the inverter,0 Ohms,Removed the grnds from the inverter to see if this was the problem,no.If I use the frame of the inverter ,I still get 138V.Might try the blue items that you talked about,and yes I am still smart enough to make sure the power is off,like my balls the way they are.Thanks

[Ervin R Dilly]

Just a follow up Rob,it was in the inverter and they are in the process of taking care of it.

[Rob Beckers]

Good to hear Ervin!

[Ervin R Dilly]

Thanks Rob,stated it was moistor welated