Do the Z 1000s require an external circuit breaker to effectively do their job.
No they do not. The Z1000 breaker is more than adequate.
They do require that you remove power to reset them, also, which is another safety factor.
No, that's not entirely accurate. As soon as the issue that caused the breaker to trip is resolved, the Z1000's breaker may be manually reset. Requiring the manual reset is the safety feature.
