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diy solar

ABB PVI 3.0 inverter low RISO in the mornings w used solar panels

brandonoh777

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Oct 26, 2020
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Hello i have a 100% made form used components grid tie system. 30 250W Canadian solar used panels and a used APP PVI 3.0 inverter. got everything hooked up and mostly running well but i am having the dreaded RISO low messages especially in the mornings with moist conditions.. Right now its just one string of 7 panels and one string of 8 on each of the separate MPPT channels. I have read and watch YT videos on why this happens and i am understand it more and more as i go along.... so it comes form low insulation/resistance conditions (for whatever reason usually moisture) from the DC side to earth ground.. problem i tested it a day or 2 with no ground on the DC side (yes i know this is a not recommended condition) and the panels pretty well electrically insulated form the actual ground (the frames) and frames isolated form each other. And i still get low riso values for the 1st third of the day. How can current be leaking to earth when the panels are isolated from the earth and no ground is connected to the inverter? I have seen the voltmeter each lead to frame test (in direct sunlight) and your supposed to see rapidly decreeing voltage readings down to near 0 and stay there if everything is the way it should be.... i will be testing each panel with this test in the future. Have any of you had similar problems with transformerless grid tied inverters? are used panels likely always going to lease some current? and the min value seems to be quite small at least for start up....the crazy thing is if it eventually boots up and gets running and then is directly rained later on in the day doesn't give any riso alarms and keeps right on going.

brandon
 
All panel need to be bonded together and grounded.
 

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  • Grounding panels.pdf
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i understand that.... this is still in R/D trying to trouble shoot this RISO issue... you are saying them not being grounded right now is causing the current leakage to earth ground?
 
great so all i am going to get here is "panels needed to be grounded...bonded and grounded"....this is something i already know...what i currently dont know is how/why current can be leaking to earth ground if there not grounded and fully insulated form the earth...i posted here to learn more about this situation not to re hear what i can read in the Manuel yes I UNDERSTAND they panels need to be grounded and bonded i said that in the beginning.....what i currently dont understand is what is causing the low riso problems...if them not being grounded and bonded is causing the low riso condition then please just a brief explanation as to how/why that may be the case?
 
what is causing the low riso problems.
Poor connections between panels.

SMA provides a method for locating your ground fault.



The fault could just be down to very bad weather because the customer finds it difficult to accept that the very nice lads who installed their system could have left a botched job behind them. The fact is, many nice people are poorly trained. A suitably designed and installed solar array should stand up to the weather.

Badly fitted connectors allow water ingress, which leads to corrosion. Corrosion of the connectors introduces an electrical resistance in the connections. This causes the connectors to heat up, which can be a fire hazard. Often the inverter will detect a leakage current and will report an insulation resistance fault (also known as Riso or isolation fault). The inverter will shut down to reduce the likelihood of fires.
 
this is a FULL DIY system i installed it. I have done that test individually on each panel in the string and found being that they are used panels many of them have current leakage from leads to frame. Is this riso test a function of transform less inverters or is it a function on all most of them? Like i said i never had this issue with the lower voltage GTI's and the panels conceded in parallel low voltage DC side (24-30v)
 
The other strange occurrence is if it successfully starts up in the morning and then later on the day the panels get directly rained on (very wet out there) as long as the inverter has already started up and has been running for part of the day it does not give a riso error seems to mainly be an issue at 1st start up whenever that is at the beginning of the day...sometimes 8am....sometimes 11am sometimes not till 3pm or not at all but will start up the next day
 
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