Discuss Two SB4000tl-20s on the same phase in the Solar PV Forum area at ElectriciansForums.net

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dave hodson

I am installing two sb4000tl-20s on the same phase. Only one array was ready so I put one inverter on-line. No problems. In the week it took to return to site, the single system had generated 99Kwh. When the second inverter went on-line (same phase), both systems looked normal, for a while. Then they started to 'bounce'. When both were on line, it was arbitrary which one would drop out, back-off then come back on-line. I eventually switched the second one off and the first came back on ok. I have applied for a 'grid guard' code but with the grid voltage already at 248V, what would the settings for the two inverters have to be for them to operate together? Any help would be much appreciated.
 

BruceB

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Sounds like cables not thick enough and/or supply cannot take total current without voltage rising beyond limits.
 

Worcester

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Did you get G59 or G83 approval to connect?

G59 cuts out at a lower voltage that G83.

We've done many many multiple inverter installtions, and the only time we see inverters dropping out like that is when they are hitting the G59 limits. 2 Causes, 1) incoming voltage high, or 2) undersized wiring.

We've never had 2) we tend to oversize, so as to minimise any possible voltage drop - even 1% (2.3V ) could be too much in some instances certainly 3% will cause problesm.

We have had 1) high iincoming voltages and the only solution is to get the DNO to reduce the incoming.

If you got G83 permission to connect, then voltgae drop out is unlikely to be the problem.

Note, without written approval from the DNO you arent allowed to simply change an inverter from G59 to G83.
 

jason121

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DNO have stopped altering voltages in my area. Have to alter the settings on the inverters. I hope you have approval in writing.
 
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dave hodson

Contacted DNO today. Awaiting reply. In the meantime, I will be increasing cable sizes to 10mm from the 4mm I installed. Reason for 4mm is the run is only 2mt to the DB. Thanks everyone. You have all been most helpful. I'll post the results when I get them both online.
 
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