Whole-Home Surge Protection Under the 2023 NEC: Selection, Sizing, and Installation for Long Island Jobs

Updated: October 21, 2025

~18 min read • ~3700 words • Flesch ~60

TL;DR: The 2023 NEC requires an SPD at dwelling services. Pick a UL 1449 Type 1 or Type 2 unit with In ≥ 10 kA, MCOV that matches the system, and SCCR ≥ available fault current. Mount it at the service or feeder panel per the label, keep leads short, and document the install. Coordinate with Long Island AHJs for placement and any local amendments. Stock one extra unit to swap if the indicator shows end of life.

Why it matters

Long Island homes see more than pretty sunsets and salty air. We also get grid switching, coastal storms, and plenty of sensitive electronics. A strong surge protective device plan protects panels, HVAC boards, EV chargers, and smart-home gear. It reduces callbacks, helps pass inspections, and keeps your customer’s downtime short.

Start at the service where the energy enters the building, then protect downstream where it makes sense. Many modern load centers accept snap-in SPD kits, which makes the work cleaner and faster. For product choices and availability, browse our AC surge protective devices category early in your planning.

New York jurisdictions follow the NEC with local amendments. Suffolk and Nassau may apply their own interpretations. Always confirm what your local inspector expects for location, type, and indicator requirements before you quote.

Fundamentals

What an SPD does. An SPD limits transient overvoltage by clamping the surge and diverting it safely. That means lower stress on equipment and fewer failures after storms or utility events.

Types and where they land. A Type 1 SPD is listed for installation on the line side or load side of the service disconnect. A Type 2 SPD is listed for the load side only. Type 3 devices are point-of-use at receptacles or equipment. For whole-home protection, focus on Type 1 and Type 2 at the service and key subpanels.

Key ratings. Verify UL 1449 listing. Check MCOV (maximum continuous operating voltage) against the system voltage. Confirm In (nominal discharge current) meets the 10 kA minimum for dwelling services under the 2023 code. Match SCCR (short-circuit current rating) to available fault current at the installation point. Remember enclosure environment. NEMA 1 is for dry indoor spaces. NEMA 3R or better is for outdoor equipment.

Lead length matters. Keep conductors as short and straight as possible. Short leads reduce let-through voltage, which is the whole point of installing an SPD in the first place. Use dedicated breakers or terminations as the manufacturer instructs.

Integrated vs stand-alone. Many load centers offer factory SPD kits that occupy breaker spaces. Others accept external SPD cans next to the panel. Either can meet code when listed, installed per the label, and located correctly.

For quick compatibility checks on panels and kits, see our Load Center Surge Protection Devices and Load Centers pages.

Code & compliance (NEC 2023 refs)

Dwelling services. NEC 230.67 requires a surge protective device at dwelling unit services. Review 230.67(A) for scope, (B) for location, and (C) for the minimum 10 kA nominal discharge current. Section 230.67(D) covers replacement requirements and (E) covers the connection method. The device must be listed for the application and installed per its label, which ties back to 110.3(B). Make terminations per 110.14.

Feeders and outdoor feeders. Where feeders supply panels in other buildings or outdoor equipment, check 215.18 and 225.42. An SPD at the feeder-supplied panel can protect that distribution and downstream loads. Follow Article 242 for selection and installation specifics.

General SPD rules. Article 242 is your home base. See 242.2 for definitions, 242.6 for listing, 242.8 for short-circuit rating, and 242.9 for indications. Part II covers installation and connection. For grounding and bonding references, follow the equipment bonding in Article 250 and the manufacturer’s diagram. Some meter-main combos require line-side rated Type 1 units. Others require load-side connections. Your label rules the day under 110.3(B).

Indicators and replacement. Most whole-home SPDs include visual status. Per 242.9 the indicator must be visible, and when it shows end-of-life the device must be serviced or replaced. For service work on existing homes, if the main panel is replaced, 230.67(D) requires that a code-compliant SPD be provided at that time.

Local adoption. Long Island AHJs may have enforcement notes that affect placement or acceptable models. Document your plan. Confirm with the inspector when the service is unusual, such as networked meter stacks, CT cabinets, or service equipment outdoors feeding indoor distribution.

Selection steps

Step 1: Identify the installation point. For a dwelling service, plan the SPD at the service equipment per 230.67. If the service equipment is integrated with the meter, select a Type 1 unit that is listed for line-side or service-side use if required. For feeder-supplied subpanels, apply 215.18 and install the SPD at the feeder panel location. For outdoor feeders, review 225.42.

Step 2: Choose Type 1 or Type 2. If the device will land line side or you need the flexibility to mount ahead of the main disconnect where permitted, select Type 1. If you will land on the load side at a breaker or lugs inside the service equipment, Type 2 is appropriate. Either way, verify the device is listed to UL 1449 for the intended use and environment.

Step 3: Match electrical characteristics. Confirm the system is 120/240 V single phase for most homes. Select an SPD with MCOV values that exceed the nominal system voltage but are appropriate for clamping performance. Verify SCCR is not lower than the available short-circuit current at the panel. If the available fault is 22 kA at the service, then the SPD SCCR must be at least 22 kA. Check the device label for SCCR and required overcurrent protection if any.

Step 4: Meet the 10 kA In requirement for dwellings. NEC 230.67(C) sets a minimum nominal discharge current of 10 kA for dwelling services. Confirm the published In on the datasheet meets or exceeds 10 kA. Many residential SPDs list 10 kA or 20 kA. Do not assume. Read the table.

Step 5: Select enclosure rating and form factor. Use NEMA 1 for dry indoor locations. Use NEMA 3R or better for outdoor service equipment. For a tidy install, consider panel-specific SPD kits when replacing or upgrading a load center. For universal use or tight quarters, select a compact stand-alone can.

Step 6: Plan the conductors. Use the conductor size and type specified by the manufacturer. Keep the leads short and straight. Aim to land on a dedicated breaker or terminals as instructed. Long leads raise let-through voltage and reduce protection. Lay out the SPD on the drawing so the crew can keep the path direct.

Step 7: Confirm accessories. Check that you have bonding jumpers, lugs, and labels ready. Stock a spare in case the indicator shows end-of-life during commissioning. For convenience, our Grounding & Bonding section includes ground clamps and terminal lugs that installers often need the same day.

Step 8: Document the choice. Record make, model, Type, MCOV, SCCR, In, location, and the breaker size or lugs used. Add a note to the panel schedule that identifies the SPD. This avoids confusion during service calls and shows intent during inspection.

Parts and panel kits mentioned here can be sourced on our Load Center Surge Protection Devices page and in Load Centers. For specific models, check stock on typical contractor favorites like the Intermatic and Leviton families in our catalog.

Sizing and configuration examples

Example A: 120/240 V, 200 A dwelling service. The home has a 200 A main breaker panel indoors. Utility data and a quick calc show available fault current at the service of 22 kA. Select a UL 1449 Type 2 SPD listed for 120/240 V split-phase with MCOV of 150 V L–N and 300 V L–L or higher. Verify In ≥ 10 kA per 230.67(C). Check that SPD SCCR ≥ 22 kA. If the SPD SCCR is 50 kA, it clears the requirement with margin. Land the device on a 2-pole breaker sized per the label, often 20 A or 30 A, and route conductors to keep the total path length as short as practical.

Shown math, SCCR check. Available fault current at service I_sc = 22 kA. Required: SPD SCCR ≥ I_sc. Choose SPD SCCR = 50 kA. Since 50 kA ≥ 22 kA, requirement satisfied. Units consistent: kiloamperes on both sides.

Lead length target. If the manufacturer guidance states performance data assumes 18 in leads, aim for 18 in or less. If a sloppy layout doubles the length to 36 in, the let-through voltage typically rises. While the exact increase depends on the model, a common rule of thumb is that each extra foot can add meaningful inductive voltage during a surge. Place the SPD to minimize distance. Plan the breaker position before you start bending pipe.

Shop panel specific kits in Load Center Surge Protection Devices, plus breaker spaces and accessories in Load Centers.

Example B: Feeder to a detached garage subpanel. The dwelling service is compliant with 230.67. A 100 A feeder supplies a garage subpanel. Under 215.18 the installer adds an SPD at the garage panel to protect branch circuits for tools and a mini split. System is still 120/240 V. Use a Type 2 SPD, MCOV values that fit the system, In ≥ 10 kA preferred even if not a service location, and SCCR ≥ available fault current at the subpanel. If the calculated available fault is 10 kA at the garage, an SPD with SCCR 22 kA covers it. Locate the SPD at the top spaces near the feeder breaker stabs to shorten leads.

Need grounding hardware and labels for the garage job too? See Grounding & Bonding and stock Ground clamps and Terminal lugs with the order.

Example C: Outdoor meter-main combo. The meter-main sits outside on a coastal wall. Select a Type 1 SPD if the label or AHJ requires a line-side capable unit. Confirm NEMA 3R or better enclosure. If the SPD has a remote indicator option, land the dry contacts inside for an alarm panel or smart relay. Reference 230.67 for the service requirement and 242.9 for indication rules. When space is tight, a compact can with side knockout may save inches and reduce conductor length.

Installation and wiring notes

Follow the label, always. 110.3(B) requires installation per listing and labeling. If the SPD label calls for a dedicated 2-pole breaker, do not share with other loads. If it allows landing on service lugs, verify torque and conductor size per 110.14.

Conductor management. Keep the conductors short and straight with smooth bends. Avoid coiling extra length. If pigtails are long from the factory, route directly to the breaker or lugs. Use the manufacturer’s recommended gauge, usually copper conductors. Bonding and equipment grounding must follow Article 250 and the panel diagram.

Enclosures and environment. NEMA 1 works for dry indoor. Use NEMA 3R outdoors. Seal penetrations to keep moisture out. On ocean-side jobs, corrosion can shorten life. Stainless screws and listed fittings help, and a drip loop prevents water from tracking along conductors.

Breaker sizing. If the SPD requires a breaker, match the size specified on the label. Many residential SPDs call for 20 A or 30 A, 2-pole. Some integrated kits use a special plug-on position that is not a standard breaker space. Check the load center’s book before the truck rolls. You can browse kit compatibility in Load Center Surge Protection Devices.

Labeling and documentation. Apply the SPD label provided. Add an entry in the panel schedule like “SPD – Service Surge Protective Device.” Take a photo of the routing and the indicator lights after energizing. Store photos with the job packet for inspection and warranty support.

Testing, commissioning, documentation

Pre-energize checks. Confirm torque on lugs per the SPD and panel instructions. Verify breaker rating and that conductors match the label. Confirm neutral and equipment grounding conductors are landed as shown in the diagram for 120/240 V systems.

Power up. Energize the panel and verify the SPD’s visual indicator is in the normal state. Some models have a test button or status contacts. If contacts are provided, verify continuity state matches the indicator and note it on the startup form.

Recordkeeping. Document make, model, Type, MCOV values, In, SCCR, breaker size if used, and the exact location. Insert photos in the PDF job packet. For Long Island inspections, this paperwork helps if the AHJ asks for listing proof or to confirm In ≥ 10 kA at a dwelling service per 230.67(C).

Troubleshooting

Indicator shows end of life at startup. Do not ignore it. Kill power, follow the manufacturer’s steps, and replace the SPD. Common causes are miswiring or shipping damage.

Breaker trips when the SPD is connected. Check that you used the correct breaker type and rating. Verify conductors are on the right terminals. Inspect for nicked insulation or a pinched lead behind the deadfront.

Electronics still failing downstream. Verify lead length. If the SPD sits far from sensitive loads, consider adding a second SPD at a critical subpanel. Confirm equipment bonding and surge reference paths are intact, especially on metallic raceways between buildings.

Buzzing or heat at the SPD. That is not normal. De-energize, re-torque per spec, and replace if damage is visible. Check available fault current data and confirm the SPD SCCR is adequate.

Common mistakes

• Buying a non-listed device or ignoring the UL 1449 marking.
• Forgetting the 10 kA nominal discharge current minimum for dwelling services in 230.67(C).
• Installing an SPD with SCCR below available fault current.
• Excess lead length that raises let-through voltage.
• Placing the SPD only at the service when feeders supply sensitive loads far away.
• Skipping documentation, which slows inspections and future service calls.

Parts to stock + Shop at Revco

• AC surge protective devices in Type 1 and Type 2 form factors.
• Load Center Surge Protection Devices that snap into common panels.
• Load Centers for panel replacements that trigger 230.67(D).
• Intermatic IG series and Leviton residential SPDs for fast swaps.
• Grounding & Bonding hardware, Ground clamps, and Terminal lugs.

Need availability on Long Island today? Call our counter team at (631) 283-3600 and we will stage the order for pickup.

When to call the AHJ or an engineer

Coordinate early for service upgrades, meter-main combos, CT cabinets, high available fault current, medical or lab equipment, or multi-building feeders. Ask the AHJ how they interpret 230.67(B) on location when service equipment and main disconnect are not in the same enclosure. When short-circuit current is high or service geometry is unusual, an engineer can validate SCCR, conductor routing, and equipotential bonding.

Safety disclaimer

Always verify requirements with your Authority Having Jurisdiction and the current manufacturer instructions before you order or install.

FAQ

Do all homes need a whole-home SPD under the 2023 NEC? Yes. 230.67 requires an SPD at dwelling unit services. Location and type must follow the label and Article 242 rules.

What is the difference between Type 1 and Type 2? Type 1 can be installed on the line side or load side where listed for it. Type 2 is for the load side only. Either can satisfy 230.67 when installed per listing and labeling.

What does nominal discharge current In mean? In is a test value under UL 1449 that indicates the device’s endurance at a specified surge current waveform. For dwelling services, select In ≥ 10 kA per 230.67(C).

Is one SPD enough for a large home? Often yes at the service, but long feeders to critical subpanels or outbuildings may benefit from an additional SPD at the remote panel to reduce let-through voltage.

Do subpanels require SPDs? The code requirement is at the dwelling service. Adding SPDs at feeders or subpanels is a design choice that can improve protection for distant sensitive loads, and Article 242 governs selection and installation.

How short should the leads be? As short and straight as practical. Many manufacturers illustrate 18 in or less. Place the SPD to reduce total path length.

What if the main panel is replaced during a service upgrade? 230.67(D) requires that the service be provided with a code-compliant SPD as part of that replacement.

How do I prove compliance during inspection? Show the product label with UL 1449 listing, the manual indicating Type and MCOV values, your panel schedule entry, and photos of the installed device and indicator state.

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.

Author: Revco Editorial Team — Electrical Content Editor
Technical review: Pending — add approved name/credential
Contact: (631) 283-3600

Sources

1. NFPA. NFPA 70 National Electrical Code, 2023 Edition. Accessed via NFPA free access portal. Retrieved October 2025.
2. NFPA. How to access NFPA codes for free. Retrieved October 2025.
3. IAEI. Article 242 and 230.67 updates overview. Retrieved October 2025.
4. EC&M. 2023 NEC changes for Surge Protective Devices. Retrieved October 2025.
5. NEMA. UL 1449 and SPD application guidance. Retrieved October 2025.
6. NEMA. SPD locations and selection references. Retrieved October 2025.
7. Eaton. Residential surge protection and 2023 NEC notes. Retrieved October 2025.
8. Schneider Electric. 2023 NEC surge protection guidance. Retrieved October 2025.
9. ABB. Overvoltage protection and installation indicators. Retrieved October 2025.
10. Minnesota DLI. 2023 code clarification for SPDs at dwelling services. Retrieved October 2025.