SPD Types and Surge Protector Nameplate Markings
Interpret North American SPD Type 1, 2, and 3 descriptions and markings such as MCOV, VPR, In, and SCCR without assuming product interchangeability.
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North American SPD types
This page uses the North American UL 1449 type context. Similar type names in another standards system do not establish the same installation or test requirements.
| Type context | General application description | Do not infer |
|---|---|---|
| Type 1 | A permanently connected SPD evaluated for the documented service-side or load-side application | Permission to install at any point, in any system, or without the specified protection. |
| Type 2 | A permanently connected SPD for its documented load-side distribution application | Interchangeability with a Type 1 product solely from its surge-current headline. |
| Type 3 | A point-of-utilization SPD with applicable installation conditions | That it replaces upstream protection or is suitable for arbitrary hardwired locations. |
| Component or assembly-specific SPD | A product intended for incorporation or use in specified equipment | Approval as a standalone field-installed device or in every panel. |
The type is one field to check, not a ranking of overall protection quality. Confirm the exact product certification, connection arrangement, and installation location in its current instructions.
Nameplate parameter lookup
| Field | What it describes | Separate from |
|---|---|---|
| Nominal system voltage / wiring configuration | The documented system and connection arrangement | A physically similar system having a different neutral or grounding arrangement. |
| MCOV | Maximum continuous operating voltage for the specified mode | The nominal supply voltage and a transient clamping/let-through value. |
| VPR | A voltage protection rating under specified test conditions | A guaranteed voltage at every downstream load in the installed system. |
| In | A nominal discharge-current rating in the stated test context | Normal load current, assembly fault current, or every advertised surge rating. |
| SCCR | Short-circuit current rating under stated conditions | A surge discharge-current rating or the interrupting rating of another device. |
| Protection modes | The documented conductor-to-conductor paths protected | An assumption that all possible modes exist in every device. |
| Status / disconnect / protective-device instructions | Product-specific operation and installation conditions | A universal indicator-color legend or universal breaker choice. |
Check the complete application
- Record the exact supply system, voltage, connection configuration, location, and available fault-current information.
- Match the product type, system rating, protection modes, SCCR, and installation instructions.
- Check the specified upstream protection, conductor/lead arrangement, equipment compatibility, enclosure conditions, and status monitoring.
- Retain the product documentation and commissioning record. Resolve missing data before selection or installation.
A large kA marketing value does not answer all these questions. This reference does not size an SPD, establish lightning protection for a building, or guarantee equipment protection.
The historical UL guide provides category background; use current certification and product instructions for a present application. Continue with breaker markings, terminal markings, and the job record as applicable.