NEC 2014 edition and 2017 edition National Electrical Code requires PV systems to have arc fault circuit interruption (AFCI) protection. AFCI protection is achieved by detection of an arc and immediate DC shutdown, at the string, combiner, or inverter level.
Some inverter manufacturers and other third-party devices have implemented solutions into their products, however some solutions experience false detection known as 'Nuisance Tripping'.
Being module-level (MLPE) devices, Tigo MLPE can not detect arc-fault, but some models can help mitigate damage.
There are 2 possible triggers of AFCI, each results in DC disconnect:
- Actual arc fault detected.
- False detection, sometimes due to noise (rapid changes of voltage) on the string. This 'noise' is sometimes interpreted as an arc fault, because the noise has similar characteristics as a real series arc generates, on voltage.
Tigo's TS4 models can be divided to 2 types, electrically:
- Electrically Passive:
- TS4-D, TS4-M, TS4-R-M: are 100% electrically passive. This because only diodes or power measurement circuitry is involved.
- Electrically, they behave just like PV modules without any MLPE device. Therefore, they can not produce voltage changes including 'noise' interpreted by AFCI detector. They can not cause false arc-fault detection.
- Electrically Active:
- TS4-S, TS4-R-S, TS4-O, TS4-R-O, TS4-L, TS4-F and TS4-R-F
- They perform disconnect, and O and L models optimize. Therefore, they can effect string voltage.
- Both Tigo and independent third-parties testing is performed to verify there are no false AFCI issues.
- They are compatible with the vast majority of inverters with AFCI detection.
Research by Sandia National Laboratories investigated, and found multiple reasons for nuisance (false) arc-fault detection. Most causes were unrelated to optimization. Sandia Nation Labs Report is here.
f you have a specific question regarding an inverter equipped with AFCI that is not listed above, please email complete specific inverter model, and specific questions to: firstname.lastname@example.org
*ES50, ES75, ES110 and ES170 are retired product since early 2013. The ES series was fully compatible with all the inverter technologies, which did not have Arc-fault detection at the time. As of the article creation date, they are not known to be compatible with modern inverters that have AFCI detection.
**2ES50, 2ES75 are retired products since mid 2016. The 2ES series was fully compatible with all inverter technologies and AFCI devices which were available on the market at the time of manufacturing.
Other Inverters with AFCI detection
Over time, more inverter models are being tested for AFCI compatibility.
To see which inverters have been successfully tested with Tigo, see: "UL PVRSS certified inverters with Tigo"