Supplemental Protectors are not intended to provide branch circuit protection and are limited to applications where branch circuit protection is already provided or is not required.
Supplemental Protectors, according to their scope of evaluation, are not evaluated for performance to provide branch circuit protection.
This consideration alters the content in the performance requirements and in general
would allow for more flexibility in the requirements than what would be allowed for a device being evaluated for branch circuit protection.
Look for the proper markings on Din-Rail Circuit Breakers to properly identify what is a Circuit Breaker and what is a supplementary protector.
Here are the CSA & UL Standards:
Branch Circuit Protection:
Products evaluated according to the UL 489 Standard for molded case circuit
breakers are listed for branch circuit protection. Branch circuit protection must be
provided for the conductors supplying utilization equipment in accordance with the NEC.
On OEM products, circuits exiting the control panel must be considered as branch circuits, as well as circuits supplying receptacles in the control panel.
The CSA (Canadian Standards Association) C22.2 No. 5.1 standard closely corresponds to UL 489. Products evaluated according to this CSA standard are intended to protect branch circuits in accordance with the Canadian Electrical Code
(CEC).
Branch Circuit Protection for DC:
UL 489A corresponds to requirements "covering single-pole or multi-pole DC circuit-breakers intended for use as branch circuit overcurrent and short-circuit protection in communications equipment."
Supplementary Protection within the Equipment:
Products evaluated according to UL 1077 Standard for supplementary protectors are recognized components which carry conditions of acceptability and therefore have limited application without further investigation by the certification organization listing the final product.
Supplementary protectors are used to protect specific loads more closely rated to the utilization equipment. OEM products may use
these devices for protecting sensitive electronic equipment or other equipment that requires unique or specific overcurrent protection.
A UL 1077 Recognized supplementary protector is not a substitute for a branch circuit overcurrent protective device listed to UL 489.
UL 1077 Recognized products must be used in conjunction with branch circuit protection when
wiring connected to the supplementary protector exits the equipment to external devices such as receptacles or motors.
The CSA C22.2 No. 235 Standard is equivalent to the UL 1077 Standard.
Tony Moscioni
Electrical Inspector
Electrical Safety Authority
