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AFCI Compliance

  • Updated

This article introduces the concept of AFCI Compliance, and confirms Tigo compatibility.

Contents: 

 

What is AFCI?

Arc Fault Circuit Interruption (AFCI) is required by the National Electric Code (NEC) as of the 2014 and 2017 editions. It is achieved by detection of an arc and immediate DC shutdown at the string, the combiner, or the inverter level.

In recent years, Inverter manufacturers and third-party devices have undergone complete design changes in order to comply with these standards. These include various AFCI solutions (some successful and others not). Some of the products can experience false detections commonly referred to as 'Nuisance Tripping.' If you are experiencing issues with any of these products, you will want to reach out to the OEM (original equipment manufacturer) to see if there are any updates for their AFCI solution. 

 

Research by Sandia National Laboratories found multiple reasons for nuisance (false) arc-fault detection. Most causes were unrelated to optimization. 

To review which inverters have been successfully tested with Tigo, see: UL PVRSS certified inverters with Tigo

 

AFCI Triggers

There are 2 possible triggers  of AFCI (each results in a DC disconnect):

  1. Actual arc fault detected
  2. False detection, sometimes due to noise (rapid changes of voltage) on the string. 

The term 'noise' refers to any combination of electrical functions or interference a system's technology may experience. These noises can be interpreted as an arc fault, because they may have similar characteristics as a real series arc generates, on voltage.

 

Retired (legacy) Products

This is a brief list of Tigo products that were designed and created, prior to the changes in the NEC code. These products may not be compatible with certain inverters or charge controllers: 

ES series - When released, the ES Series was fully compatible with all the inverter technologies, which did not have Arc-fault detection at the time. They are not known to be compatible with modern inverters that have AFCI detection.

  • MM-ES50 (retired 2013)
  • MM-ES75 (retired 2013)
  • MM-ES110 (retired 2013)
  • ES170 (retired 2013)

 

The 2ES series When released, the 2ES Series was fully compatible with all inverter technologies and AFCI devices which were available on the market at the time of manufacturing.

  • MM-2ES50 (retired 2016)
  • MM-2ES75 (retired 2016)

 

Frequently Asked Questions (FAQ)

Are the TS4 Flex MLPE products compatible with AFCI? 

Tigo's TS4 models are compatible with all modern AFCI requirements. Tigo MLPEs (themselves) cannot detect arc-fault, but some models can help mitigate damage.

The Flex MLPE family can be divided to 2 types, electrically:

Electrically Passive: Only Diodes or Power Measurement is provided. 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.

  • TS4-D
  • TS4-M
  • TS4-R-M
  • TS4-A-M

Electrically Active:

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.

  • TS4-S
  • TS4-R-S
  • TS4-O
  • TS4-R-O
  • TS4-A-O
  • TS4-L
  • TS4-F
  • TS4-R-F
  • TS4-A-F
  • TS4-2F
  • TS4-R-2F
  • TS4-A-2F

 

How can I upgrade my system to be compatible with AFCI? 

There are several existing solar products that were produced prior to the change in the NEC Code. These products may not be suitable for systems with modern Inverters that meet the current standards.

At this time, there is no easy solution to make older products compatible. Installing a new inverter on your system may require a full modernization of other products, in order to meet the new standards. 

However, if you have an older system (with an older inverter), please know that your system may be "Grandfathered" in, and may not be required to make any updates or upgrades in AFCI functionality.

 

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Support

If you require design assistance, please contact Tigo's Sales Engineering Team.

If you are experiencing issues with an existing Tigo system, please contact our Support Team.

 

 

 

 

 

Related Articles:

https://support.tigoenergy.com/hc/en-us/articles/202368968-Inverter-Compliance

https://www.tigoenergy.com/downloads/inverter-compliance-letters/

https://www.sma-america.com/partners/knowledgebase/pv-arc-fault-circuit-interrupter.html

https://support.tigoenergy.com/hc/en-us/articles/225227067-SMA-Tigo-Compatibility-Guidelines

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