ZSI works by providing a signal to the upstream breaker in order not to trip if the downstream breaker sensed the fault. NSX100, NSX160 and NSX250 can only be on the downstream level of the zone selective interlocking architecture; meaning that they can only be in relation with an upstream circuit breaker (ZSI OUT). The NSX100-250 cannot be used to receive a signal from a downstream circuit breaker as they can only trasnmit signlas to upstream higher rated breakers (NSX400 to NSX630). But NSX100~250 cannot be used to send and receive ZSI signals as these small frame sizes are only used to transmit signals. So the questioned configuration cannot be used. For more details on ZSI, please refer to pages 71 and 72 of the attached Compact NSX Micrologic User Guide.

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