SMA 4000TL 'Insulation resistance' error

[digital48]

I've recently found the green light flashing and the red light on on our SMA 4000TL with the message 'Insulation resistance, check generator' on the display.

Checking the ERROROB2.CSV files I can see that this isn't the first time it has errored in this way, it has happened on odd occasions for several months. The most recent events are listed as:

SB 4000TL-20 78 2.1E+09 13/01/2017 09:06 29180 35 Outgoing Info DC Side Insulation resist.
SB 4000TL-20 78 2.1E+09 17/01/2017 09:11 29249 35 Incoming Warning DC Side Insulation resist.
SB 4000TL-20 78 2.1E+09 17/01/2017 09:11 29249 35 Incoming Error DC Side Insulation resist.
SB 4000TL-20 78 2.1E+09 17/01/2017 09:11 29249 35 Outgoing Info DC Side Insulation resist.
SB 4000TL-20 78 2.1E+09 01/02/2017 09:04 29509 35 Incoming Warning DC Side Insulation resist.
SB 4000TL-20 78 2.1E+09 01/02/2017 09:04 29509 35 Incoming Error DC Side Insulation resist.
SB 4000TL-20 78 2.1E+09 01/02/2017 09:04 29509 35 Outgoing Info DC Side Insulation resist.
SB 4000TL-20 78 2.1E+09 13/02/2017 08:55 29780 35 Incoming Warning DC Side Insulation resist.
SB 4000TL-20 78 2.1E+09 13/02/2017 08:55 29780 35 Incoming Error DC Side Insulation resist.

Is anyone able to offer an explanation and suggest what might need to be done? The installation is five years old and has 21 Canadian Solar panels on three strings.

 

[SparkyChick]

Hope this helps.

In essence you need to be a qualified electrician and you should follow the testing procedure in the video to identify which string (or strings) is causing the problem, which they describe as an earth fault. Then go round and check all the connections/cabling for that string.

 

[Gavin A]

it's quite common for that to happen on very cold damp winter mornings on start up, I wouldn't worry about it at that frequency. The insulation resistance value can be lowered from 1MOhm to 500Ohms to reduce the frequency of it happening, but it's not worth the call out fee at that frequency.

 

[digital48]

Thanks. I'll keep an eye on it. Out of interest, what would it cost (ball park...) to reduce the insulation resistance value?

 

[Gavin A]

call out fee - ours is £150 + travel time.