| Type 1 Service-Entrance SPD | On the supply side of the main service disconnect, where permitted by the electrical authority | 120/240 V AC | 10–20 kA per mode is common | Reducing externally generated surges, including those entering through utility or service conductors | Installed by a qualified electrician using equipment listed for the intended service location | Check the visual status indicator and inspect the enclosure; do not open energized equipment | Replace after a known major surge, lightning event, physical damage, or a failed status indicator |
| Type 2 Whole-Panel SPD | Load side of the main service disconnect, commonly at the main distribution panel | 120/240 V AC | 20–40 kA per mode is common | Protecting branch circuits, appliances, electronics, and building wiring from incoming and internally generated transients | Connected to the appropriate circuit breaker, neutral, and grounding conductors according to the installation instructions | Use the built-in indicator; confirm that the associated breaker is on and arrange professional inspection if the indicator changes state | Replace when the indicator shows failure, the unit is damaged, or the device has reached its stated end of service life |
| Type 3 Point-of-Use Strip | At a receptacle near sensitive equipment | 120 V AC | Usually specified by the manufacturer; often below 20 kA | Supplemental protection for computers, televisions, networking equipment, and small appliances | Plug directly into a properly grounded receptacle; avoid using extension cords or daisy-chaining power strips | Press the test or reset control if provided and verify the protection indicator; inspect the cord, plug, and outlets for heat or damage | Replace after a substantial surge, overheating, cracked housing, damaged cord, repeated tripping, or a failed indicator |
| Plug-In Receptacle SPD | Inside or directly adjacent to a wall receptacle | 120 V AC | Commonly rated in the 10–20 kA range | Protecting individual loads where a power strip is not needed | Plug into a grounded receptacle with no loose connection; keep the device accessible for inspection | Check the protection-status light and use any built-in test function described in the instructions | Replace if the light indicates failure, the unit becomes warm without a normal load, or the receptacle connection is loose |
| Data-Line SPD | At telephone, coaxial, Ethernet, or other low-voltage communication entry points | Depends on the communication system | Specified by the device for the applicable signal circuit | Limiting surges that may travel through communication cables connected to network or audio-visual equipment | Installed inline with the signal cable and bonded to the building grounding system when required | Inspect the connection, grounding path, and status indicator; verify equipment operation after installation | Replace after a nearby lightning event, visible damage, loss of signal, or a failed status indicator |
| Combination Protection System | Whole-panel SPD combined with point-of-use protection and data-line protection | 120/240 V AC power plus applicable signal-circuit ratings | Varies by each installed device | Layered protection for the electrical service, branch circuits, appliances, and communication lines | Install each component according to its listing, wiring diagram, grounding requirements, and local electrical rules | Test each indicator and inspect all grounding and bonding connections; professional inspection is recommended | Replace only the failed or damaged component unless the manufacturer specifies replacement of the complete system |