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What is the difference between a CAFI and an AFI circuit breaker?

Issue:
How is a Combination Arc-Fault Circuit Breaker (suffix CAFI or CAFIC) different than an Arc-Fault Circuit Breaker (suffix AFI or AFIC)?

Product Line:
Circuit Breakers

Environment:
QO, QOB, and HOM circuit breakers with suffixes CAFI, CAFIC, AFI, AFIC

Cause:
Some of the breakers have a suffix CAFI (or CAFIC), and are called Combination Arc-Fault Breakers. But there are also breakers that have a suffix AFI (or AFIC), and are called Arc-Fault Breakers. What is the difference?

Resolution:
First, be aware that whether it is an AFI or CAFI breaker, both types also include the thermal/magnetic protection for overloads and short circuits that a standard circuit breaker has. As to the difference in AFI and CAFI, here are the details:

AFI or AFIC Suffix
Schneider Electric (Square D) type QO, QOB and HOM circuit breakers with suffix AFI or AFIC primarily detect parallel arcing (branch/feeder).
The push-to-test button is blue or green.

The AFI breakers will trip under these conditions:
(1) The breaker detects a downstream overload or short circuit (per trip curve)
(2) The breaker detects a downstream current to ground in the range of 30-50ma or greater, regardless of the load.
(3) The breaker detects an upstream or downstream arc in that circuit that meets certain preset conditions ("arc signature"), plus at the same time the breaker is carrying 50A or more of load current, even if very briefly. This 50A maximum value used in QO and HOM AFI breakers is lower than UL1699 value of 75A for arc-fault circuit breakers.
CONCLUSION: Square D/Schneider Electric AFI Arc-Fault Circuit Breakers are designed to provide protection against overloads, short circuits, and parallel arcs (H-N), and will trip on current to ground in the range of 30-50mA or higher.

CAFI or CAFIC Suffix
Schneider Electric (Square D) type QO, QOB and HOM circuit breakers with suffix CAFI or CAFIC detect parallel arcing plus series arcing (branch/feeder/outlet).
The push-to-test button is white.

The CAFI breakers will trip under these conditions:
(1) The breaker detects a downstream overload or short circuit (per trip curve)
(2) The breaker detects a downstream current to ground in the range of 30-50ma or greater, regardless of the load.
(3) The breaker detects an upstream or downstream arc in that circuit that meets certain preset conditions ("arc signature"), plus at the same time the breaker is carrying 5A or more of load current, even if very briefly. The 5A value is per UL1699 for combination-type arc-fault circuit breakers.
CONCLUSION: Square D/Schneider Electric CAFI Combination Arc-Fault Circuit Breakers are designed to provide protection against overloads, short circuits, parallel arcs (H-N), and series arcs (H-H same phase), and will trip on current to ground in the range of 30-50 mA or higher.  
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