NEC 2023 Surge Protection at Services: How to Select and Install Type 1 & Type 2 SPDs (Long Island, NY)

Updated: October 21, 2025

~8 min read • ~1,700 words • Flesch ~60

TL;DR: For most Long Island dwellings, install a listed service-level SPD with In ≥ 10 kA per 230.67, keep leads short and straight, match the device to system voltage and SCCR, and follow 110.3(B) instructions. For light commercial or sensitive loads, layer a downstream Type 2. Document the model, date, and indications for inspection and future service. When fault current is high, or you are working on emergency systems, coordinate with the AHJ and the utility before you buy hardware.

Why this matters on the job

Power quality problems do not send calendar invites. A single transient can fry sensitive electronics, drop a POS system, or take out a boiler control. The 2023 NEC tightened surge protection at services and expanded where it is required. That affects how you spec panels, how you route conductors, and what inspectors look for on Long Island. Getting it right protects your customer and protects your schedule.

Contractors also tell us they want simple, repeatable choices. Whole-home or whole-building surge protection is now a baseline conversation on most residential and light commercial jobs. The good news: with the right rating checks and a clean installation, you can meet code and deliver real protection. If you need parts fast, browse our electrical distribution selection or swing by a Revco branch.

Fundamentals

What an SPD does. A surge protective device (SPD) clamps voltage spikes to limit the stress seen by connected equipment. It sits in parallel with the system and diverts surge energy to the grounding system.

Types you’ll see in the field. UL 1449 recognizes Type 1, Type 2, Type 3, and Type 4. For service and panel work, you’ll mainly choose between:

• Type 1 SPDs: Listed for line side or load side connection. Often used at the service equipment or meter-main. Many are hard-wired or factory-integrated.
• Type 2 SPDs: Listed for installation on the load side of the service disconnect. Typical in load centers and panelboards, including plug-on styles.

Key ratings to understand.

• MCOV (maximum continuous operating voltage): Must match the system. For a 120/240 V split-phase, make sure the SPD is listed for that system and neutral configuration.
• VPR (voltage protection rating): A performance number from UL 1449 testing. Lower is better, within reason, and should align with equipment sensitivity and project spec.
• In (nominal discharge current): The 2023 NEC sets a minimum at services. Treat In like a baseline durability indicator for repetitive surges.
• SCCR (short-circuit current rating): The SPD’s withstand at the connection point. Must be equal to or greater than the available fault current where you land it.

Tiered protection. Good practice layers a service-level SPD with downstream protection for sensitive loads or long feeders. For many homes and small commercial spaces, a solid service SPD plus prudent equipment selection gives a strong first line of defense. For facilities with controls, HVAC BAS, or IT loads, add point-of-use or panel-level SPDs as needed. See our AC surge protective devices category for options.

Code & compliance (NEC 2023 references)

Service surge protection. NEC 230.67 requires listed surge protection at dwelling unit services and service replacements. The 2023 edition clarified and expanded related requirements across occupancies and systems that matter to Long Island jobs. 230.67 also sets In ≥ 10 kA for service SPDs. Inspectors expect to see the rating on the device label or submittal.

Overvoltage protection framework. Article 242 is your roadmap. It covers listing (242.6), SCCR (242.8), indication (242.9), installation and connection (Part II, including 242.24), and routing and conductor considerations. The theme is simple: use listed gear, match it to the system, keep connections short and direct, and follow the manufacturer’s instructions per 110.3(B).

Special systems. Some systems call for SPDs even outside dwelling rules. Examples include emergency systems equipment (700.8), fire pumps (695.15), and critical operations power systems (708.20(D)). If your project includes any of these, confirm the SPD type and placement with the AHJ early.

Mechanical details that matter. Terminations must meet 110.14(D) torque. Conductor sizes and overcurrent protection must follow the SPD instructions. Labeling and indication should be visible after installation. Many inspectors will ask to see the wiring route to verify it is as short and straight as practical.

Selection steps

Follow this simple sequence to land on the right device quickly and pass inspection cleanly.

Step 1: Confirm the project scope and AHJ adoption. Identify if the job is a single-family dwelling, multifamily dwelling unit, or other occupancy with surge requirements. On Long Island, municipalities can vary in enforcement details. Get clarity from the local inspector before rough-in. For stocked options, check our load center surge protection devices.

Step 2: Choose Type 1 vs Type 2 for the location.

• At the service equipment or meter-main: Type 1 or a device listed for line side. Use when space or architecture favors a service-side install.
• Inside the service disconnect enclosure or main panel: Type 2 on the load side is common. Plug-on SPDs can speed installs and keep leads short.

Step 3: Check ratings that drive compliance and performance.

• System match: 120/240 V single-phase 3-wire is common for homes; verify the device listing for that system. For small commercial, verify 120/208 V or 277/480 V as applicable.
• In: For service SPDs, select In ≥ 10 kA per 230.67. Many modern residential units meet or exceed this.
• SCCR: Confirm the SPD SCCR meets or exceeds available fault current where installed. If you do not have a calculated value, use the gear’s series rating or the utility-provided fault estimate as a screening check and select an SPD with a high SCCR to be safe.
• VPR: Choose a device with a VPR appropriate for the loads and the spec. Lower VPR generally means tighter clamping.
• MCOV: Must be compatible with the system. Do not overspecify MCOV so much that performance suffers.

Step 4: Pick the form factor.

• Plug-on SPD that snaps into the load center bus. Fast install, short path, clean appearance. Example: a plug-on unit from a panel’s matching brand.
• Wired Type 2 mounted adjacent to the panel or service equipment. Offers brand flexibility. Keep leads as short and straight as possible.
• Factory-integrated SPD inside service equipment or a meter-main. Useful on service upgrades when space is tight.

For brand ecosystems and accessories, explore Leviton SPDs and Intermatic surge solutions. If you prefer a plug-on model, the Leviton LSPD2-T plug-on SPD is a common pick for modern load centers.

Step 5: Accessorize and plan for service. Stock a spare SPD where owners demand uptime. Keep extra filler plates, a dedicated 2-pole breaker if required by the SPD instructions, and ground or neutral bars for tidy landings. See ground and neutral bars and panelboard lugs for clean installs.

Sizing/config examples (what you’ll do most)

120/240 V single-family service. Install a listed SPD at the service equipment per 230.67. If using a plug-on SPD, install in the load center per manufacturer instructions with the shortest possible connection to the bus and neutral/ground reference. Verify In ≥ 10 kA on the nameplate and that the SPD is listed for 120/240 V split-phase. For a wired Type 2 next to the panel, keep leads short and avoid sharp bends.

Light commercial tenant with 120/208 V system. Where specified or required by the occupancy, select a Type 2 SPD listed for 120/208 V wye. Confirm SCCR and follow panelboard instructions for breaker sizing and conductor gauge. Add downstream point-of-use protection for IT racks or building automation where sensitive controls live.

Installation & wiring notes

• Mounting and location. At the service, place the SPD where the leads can be shortest and direct. For wired Type 2 devices, mount adjacent to the panel or within an approved section of the enclosure if listed for that use. Avoid tight bundles and sharp bends.
• Conductor length and routing. Article 242 points you to short, straight conductors with minimal loop area. Keep the SPD equipment grounding conductor as direct as possible to the panel’s grounding point.
• Terminations and torque. Follow 110.14(D). Use the manufacturer’s specified torque for lugs or breakers. Record torque on your job card so you can answer the inspector confidently.
• Overcurrent protection. Some Type 2 SPDs connect via a dedicated 2-pole breaker. Others are plug-on or have internal protection per UL 1449. Use only the breaker sizes and conductor gauges named in the instructions.
• Bonding and grounding. Verify the service bonding jumper and grounding electrode system are complete and tight before energizing. A poor grounding path degrades SPD performance.
• Environmental considerations. For coastal jobs or damp locations, select NEMA enclosures rated for the space and keep penetrations sealed. Salt air on the South Shore is not kind to open knockouts.

Testing, commissioning, and documentation

• Pre-energization checks. Confirm system voltage, conductor terminations, breaker sizing, and that the SPD indicator is visible after the cover is on.
• Initial power-up. Energize and verify indicator status. Many units use a green lamp for normal and red or dark for replace.
• Recordkeeping. Log the model number, serial, date of install, location, and indicator status. Keep a photo of the nameplate in the closeout package.
• Owner handoff. Show the owner or facility contact where the indicator is and what “replace” means. Leave the instruction sheet in the panel directory pocket.
• Warranty. Register the product if the manufacturer offers it. File your torque log and photos so you can support a future claim.

Troubleshooting

• Indicator shows failed. De-energize as required by the instructions and replace the SPD with an identical or approved equivalent. Before replacement, check grounding and bonding. Look for evidence of a surge event in other electronics.
• Nuisance breaker trips. Confirm the SPD is landed on the correct breaker size and type. Inspect for damaged leads or pinched insulation. If the breaker is shared, move the SPD to a dedicated 2-pole if required by instructions.
• Recurring failures. Measure or obtain the available fault current and review SCCR. Relocate the SPD to reduce lead length. Consider a higher In or a coordinated two-tier setup with panel and point-of-use protection. For quick diagnostics, skim our field troubleshooting guide.

Common mistakes

• Installing a Type 2 on the line side of the service disconnect.
• Ignoring SCCR relative to available fault current at the connection point.
• Using long, looped, or tightly bundled leads that raise let-through voltage.
• Skipping torque verification or hiding the indication behind the dead front.
• Picking the wrong system rating. For example, using a 120/240 V unit on a 120/208 V wye system.
• Forgetting the In ≥ 10 kA minimum for service SPDs required by 230.67.

Parts to stock + Shop at Revco

Keep a small SPD kit so you can finish in one visit and keep customers happy.

• Whole-home and panel SPDs: see AC surge protective devices and load center surge protection devices.
• Plug-on options matched to modern load centers, including Leviton LSPD2-T. Pair with your panel brand ecosystem, such as Leviton or Intermatic.
• Support hardware: ground and neutral bars, panelboard lugs, arc-fault breakers, and filler plates.

When to call the AHJ or an engineer

• Service upgrades and meter-mains. Coordinate SPD placement and utility clearances. Ask about available fault current so you can verify SCCR.
• Emergency systems, fire pumps, or COPS. Articles 700.8, 695.15, and 708.20(D) have special expectations for listing, placement, and maintenance access.
• Multifamily common areas and small commercial switchboards. Requirements can differ from dwelling unit rules. Confirm Article 242 details with the inspector.
• High-exposure sites. Facilities with frequent surges, long outdoor feeders, or critical IT loads may need a layered design reviewed by an engineer.

Safety disclaimer

Follow all manufacturer instructions and the 2023 NEC. Local adoption and amendments on Long Island can vary by municipality. Always verify requirements with the Authority Having Jurisdiction and the serving utility before purchasing or installing equipment.

FAQ

• Do I need an SPD on every panel in a house? The code requires surge protection at the dwelling service. Many contractors add a downstream SPD for sensitive subpanels by design choice.
• What does In ≥ 10 kA actually tell me? It is the nominal discharge current rating used in UL 1449 testing. For services, the 2023 NEC sets a minimum of 10 kA. Treat it as a durability baseline.
• Is a plug-on SPD as effective as a wired Type 2? In many residential load centers, a plug-on has the benefit of very short paths. Effectiveness depends on listing, ratings, and installation quality.
• How long do SPDs last? They wear with surge exposure. Indicators show when to replace. Sites with frequent storms or switching events will consume capacity faster.
• What is VPR in plain terms? It is the clamping level measured under a standard test. Lower VPR means tighter clamping, but device selection must still match the system and SCCR.
• Can an SPD fix bad grounding? No. You need a proper grounding electrode system and bonding. An SPD relies on that path to divert surge energy.
• Do inspectors look for labels? Yes. Expect questions about listing, In rating, and where you landed the conductors. Keep instructions on hand.
• What about 120/208 V systems in small commercial spaces? Use an SPD listed for that system and verify SCCR. Consider additional protection for IT and controls.

Code references you will actually use

230.67 requires surge protection at dwelling services and sets the minimum nominal discharge current at 10 kA. Article 242 covers listing (242.6), SCCR (242.8), indication (242.9), installation and connections (Part II, including 242.24), and routing. Special systems appear in 695.15, 700.8, and 708.20(D). Always apply 110.3(B) and 110.14(D) for instructions and torque.

About Revco Lighting & Electrical Supply

Since 1978, Revco Lighting & Electrical Supply has been helping professionals bring their projects to light—literally. As a go-to source for lighting and electrical products across Long Island, NY and nearby areas, we specialize in supporting contractors, builders, and industry experts with practical solutions and dependable service. Whether it’s a complex commercial build or a simple residential upgrade, we’re here to make sure you have what you need, when you need it.

Credits

Author: Revco Editorial Team - Electrical Content Editor

Technical review: Pending - add approved name/credential

Contact: (631) 283-3600

Sources

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2. Mersen. “UL 1449 4th Edition Location and/or Type Designations.” https://www.mersen.com/sites/default/files/files_imported_ep/TT-SPN6-UL1449-4th-Edition-Location-Type-Designations.pdf Retrieved October 2025.
3. EC&M. “NEC Requirements for Overvoltage Protection.” https://www.ecmweb.com/national-electrical-code/code-basics/article/21260858/nec-requirements-for-overvoltage-protection Retrieved October 2025.
4. Schneider Electric Blog. “2023 National Electric Code changes for surge protection.” https://blog.se.com/energy-management-energy-efficiency/electrical-safety/2023/03/27/2023-national-electric-code-changes-for-surge-protection/ Retrieved October 2025.
5. Leviton. “NEC Code Requirements for Surge Protection.” https://leviton.com/products/commercial/surge-protection/nec-code-requirements-for-surge Retrieved October 2025.
6. ABB. “Overvoltage Protection: Key Changes in the 2023 NEC.” https://search.abb.com/library/Download.aspx?Action=Launch&DocumentID=9AKK108471A0258&DocumentPartId=&LanguageCode=en Retrieved October 2025.