1. Control Circuit Protection Supplementary Protectors vs
Control Circuit Protection Supplementary Protectors vs. Miniature Circuit Breakers
UL 1077 vs. UL 489

2. What is Supplementary Protection?
Supplementary Overcurrent Protective Device –
A device intended to provide limited overcurrent protection for specific applications and utilization equipment such as luminaires (lighting fixtures) and appliances (and other equipment or for internal circuits and components of equipment). This limited protection is in addition to the protection provided in the required branch circuit by the branch circuit overcurrent protective device.
NEC2005, NFPA 70: National Electrical Code, Article 100, Definitions (70-31) Article [Overcurrent Protection] (70-84)
Definition
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3. What is a Final Overcurrent Device?
Circuit Breaker –
A device designed to open and close a circuit by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating.
NEC2005, NFPA 70: National Electrical Code, Article 100, Definitions (70-27)
Definition
Circuit Breaker (Final Overcurrent Device)
Circuit Conductors
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4. What is a Branch Circuit?
The circuit conductors between the final overcurrent device protecting the circuit and the outlet(s).
NEC2005, NFPA 70: National Electrical Code, Article 100, Definitions (70-26)
Circuit Conductors
Final Overcurrent Device
Definition
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5. What is Supplementary Protection?
Circuit Breaker
Examples
Supplementary Overcurrent Protective Device –
A device intended to provide limited overcurrent protection for specific applications and utilization equipment such as luminaires (lighting fixtures) and appliances (and other equipment or for internal circuits and components of equipment). This limited protection is in addition to the protection provided in the required branch circuit by the branch circuit overcurrent protective device.
NEC2005, NFPA 70: National Electrical Code, Article 100, Definitions (70-31) Article [Overcurrent Protection] (70-84)
Blender
Garbage Disposal
Vacuum Cleaner
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November, 2006

6. What is Supplementary Protection?
Examples
(NEC Article ) Siemens 5SX/5SY/5SP Supplementary Protectors are used to provide overcurrent protection where branch protection is already provided or, not required. Supplementary Protectors are installed as a component with, or part of, a piece of electrical equipment.
Supplementary Protectors protect equipment, not wiring systems. Typical equipment includes:
Motor Control Circuits
Control Power Transformers
Relays
Contactor Coils
PLC I/O Points
Lighting Circuits
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November, 2006

7. Circuit Breaker or Supplementary Protector?
UL 1077: UL Standard for Safety for Supplementary Protectors for Use in Electrical Equipment [CSA 22.2 No. 235]
Standards
NFPA 70: National Electrical Code
UL 489: UL Standard for Safety for Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures [CSA 22.2 No. 5]
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8. Circuit Breaker or Supplementary Protector
UL 489 – These requirements apply to molded case circuit breakers, … These circuit breakers are specifically intended to provide service entrance, feeder and branch circuit protection in accordance with the National Electrical Code, NFPA 70.
UL 1077 – These requirements apply to supplementary protectors intended for use as overcurrent; or, over- or under-voltage protection within an appliance or other electrical equipment where branch circuit protection is already provided, or not required by the standard.
Standards
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9. UL Safety Standard Differences
UL 1077: Supplementary Protector
UL 489: Circuit Breaker
● UL Recognized – Carries specific conditions for use (acceptability) that must be followed to ensure that the device will meet minimum electrical and shock requirements.
● Provides equipment (load) protection where branch circuit protection is already provided.
● Cannot be applied as a motor branch or branch circuit protection device.
● Allowed to be tested with a branch circuit device in series with the supplementary protector.
● Typically not required to close on fault conditions.
● UL Listed – Carries no conditions of use (acceptability)
● Provides branch circuit protection in accordance with the National Electrical Code. (conductor/wiring system short circuit protection)
● Motor branch circuits can be protected by a UL 489 device.
● Not allowed to rely on a series protective device for conductor protection.
● Required to close on fault conditions
Standards
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10. UL Safety Standard Differences
UL 1077: Supplementary Protector
UL 489: Circuit Breaker
● Has a typical short circuit current rating of 5,000 A, but need not have been evaluated for short circuit conditions during the recognition. May be evaluated for greater than 5,000 A and may be evaluated at any value declared by the manufacturer.
● Has no standard trip curve established by the product safety standard to ensure protection of conductors in the event of an overload or short circuit condition.
● Overload protection – 1-1/2 times rating Horsepower rating: 6 times rating.
● Spacing (UL 100, 600V, General Industrial Use): 3/8 inch through air and ½ inch over surface.
● Has minimum short circuit interrupting ratings of 5,000 A at 250 V or less; and, 10,000 A at above 250 V.
●Has trip-curve characteristics developed for protection of branch and feeder circuits.
● Overload protection – 6 times rating.
● Spacing (UL 489, 600 V): 1 inch through air and 2 inches over surface.
Standards
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11. Supplementary Protector Check List
Does the supplemental protector meet or exceed the application conditions?
BE SURE that the supplemental protector has a short circuit current rating equal to or greater than the available short circuit current of the installation.
CHECK THE VOLTAGE RATING against the system voltage. If the supplemental protector has a slash voltage rating, i.e. 480Y/277, be sure it will be properly applied. For instance, a rating of 480Y/277 volts can not be used on a 480 volt high resistance grounded wye system, 480 volt corner grounded delta system, or a 480 volt ungrounded system. It can only be applied on a 480/277 volt solidly grounded wye system.
The supplementary protector is not intended to a used as a disconnect.
Check to insure the specific time current characteristics of the supplemental protector provides the intended protection for equipment under ALL CONDITIONS.
Check List
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12. Supplementary Protector Check List
Check to insure that the supplemental protector is NOT BEING MISAPPLIED as BRANCH CIRCUIT PROTECTION
Check to insure the proper branch circuit protective device is ahead of the supplementary protector. Most supplemental protectors are evaluated under short circuit conditions with a branch circuit fuse or circuit breaker ahead of them.
Check List
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13. Advantages of Supplementary Protectors
Small Installed Size
Precise Component Protection – protects components better than conventional circuit breakers during short circuits
Resetable After A Fault (if not a fuse)
Tripping Selectivity
Fault Isolation – only part of the circuit is affected
Advantages
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14. Typical Supplementary Protector Applications
Automotive Systems
Appliances
Control Circuits
Control Instrumentation
Enclosed Panel Heaters
Lighting Circuits
Medical Equipment
PLC I/O
Power Supplies
Receptacles in Enclosed Panels
Relay/Contact Coils
Solenoids
Test Equipment
Transformer Primary & Secondary
Applications
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