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10 Best Subpanel Surge Protectors to Safeguard Your Home Electrical System
You can protect a 120/240V subpanel by installing a Type 1 or Type 2 surge protector rated 25–80 kA, wired L1-L2-N-G within 1–3 ft of the panel. Consider models like EATON CHSPT2ULTRA, Square D HOM2175SB, Intermatic AG3000, FHSPD36S, and Square D HEPD80 (HEPD80 = 80kA). Shut off main power, torque terminals per spec, and mount at eye level with LED status visible. Continue for full model comparisons and installation tips.
Key Takeaways
- Choose Type 2/SPD installed at the subpanel to protect branch circuits without occupying main breaker spaces.
- Prioritize SPDs with at least 25–80 kA surge current rating and UL 1449 (3rd ed.) listing for reliable protection.
- Match the SPD to your load‑center brand (Square D, Siemens, Eaton) for plug‑on or bus‑stab compatibility and easier installation.
- Look for clear status indicators (LED/mechanical) and thermal/fail‑safe protection so you know when replacement is needed.
- Have a qualified electrician install the SPD with proper L1/L2/neutral/ground connections and shortest possible lead lengths.
HVAC Whole House Surge Protector, Single-Phase 120/240V, 25kA per Phase
HVAC Surge Protector,Whole House Surge Protector,Single-Phase,3-Wire for 120/240V, 25KA(Surge...
- The SPD is extremely compact UL Type 1 or Type 2 Surge Protective Devices (SPDs) designed to protect Single phase (or Split phase) electrical distribution systems. It can...
- The SPD is equipped with the patented 20PTMOV which has a thermally protection and arc extinguishing technology.
- Single phase (or Split phase) (120/240Vac),25KA(Surge Capacity per Phase),200KA（Short-circuit current rating）.
You may be interested
If you manage a single-family home’s HVAC system, the HVAC Whole House Surge Protector is a strong choice because it protects 120/240V split-phase panels with 25kA per phase capacity. You’ll install this UL Listed, single-phase 3-wire SPD at a subpanel or main panel. It’s compact, UL Type 1/Type 2, waterproof plastic enclosure, and fits indoors or outdoors. Connect L1, L2, and neutral per panel diagram, torque lugs to manufacturer spec, and verify LED protection light is on. The unit uses patented 20PTMOV tech, thermally protected and arc-extinguishing, with 200kA short-circuit rating.
Best For: Homeowners or HVAC technicians seeking compact, UL-listed surge protection for single-family 120/240V split-phase panels and subpanels to safeguard HVAC systems and whole-house equipment.
Pros:
- Compact UL Type 1/Type 2 design fits indoors or outdoors and into tight panel spaces.
- High surge capacity of 25kA per phase with 200kA short-circuit rating and UL1449 5th/CSA compliance.
- Patented 20PTMOV technology with thermal protection, arc extinguishing, and LED status indicator for easy verification.
Cons:
- Designed only for single-phase/split-phase systems—not suitable for three-phase commercial services.
- Requires proper installation at the panel (L1, L2, N) and correct lug torque—may need a qualified electrician.
- Waterproof plastic enclosure may be less robust than metal housings in extreme outdoor environments.
EATON CHSPT2ULTRA Ultimate Surge Protector (3rd Edition)
Eaton CHSPT2ULTRA Ultimate Surge Protection 3rd Edition, 2.38" Length, 5.25" Width 7.5" Height
- Universally connects to any manufacturer’s load center (breaker box)
- Easy to use
- High quality product
You’ll find the EATON CHSPT2ULTRA Ultimate Surge Protection 3rd Edition best for protecting a single subpanel because it mounts directly to the breaker box and fits any manufacturer’s load center. You can install the CHSPT2ULTRA (2.38″ L x 5.25″ W x 7.5″ H, 8 oz) by turning off main power, removing the panel cover, and attaching the unit to the neutral/ground bar per Eaton instructions. You can reconnect wiring, secure the cover, and restore power. This 3rd Edition unit provides ultimate surge protection, is easy to use, and works universally with all load center brands.
Best For: Best for homeowners or electricians needing a compact, easy-to-install whole-house/subpanel surge protector that mounts directly to the breaker box and fits any manufacturer’s load center.
Pros:
- Universal compatibility — fits and connects to any manufacturer’s load center (breaker box).
- Compact and lightweight (2.38″ L x 5.25″ W x 7.5″ H, 8 oz) for easy mounting in tight panel spaces.
- Simple installation procedure (mount to neutral/ground bar, reconnect wiring) and provides 3rd Edition “ultimate” surge protection.
Cons:
- Requires turning off main power and working inside the breaker panel, which may necessitate a licensed electrician for safety.
- Limited to protecting the panel/subpanel where it’s installed — may not replace point-of-entry protection for certain whole-property setups.
- No specific electrical ratings (e.g., joule rating, response time) provided here, so users may need more technical specs to compare models.
Square D HOM2175SB Homeline SurgeBreaker Surge Protection Device (25kA, 120/240V, 1-Phase, 3-Wire)
Square D by Schneider Electric HOM2175SB Homeline SurgeBreaker, Surge Protection Device, 25kA...
- Compatible ONLY with Square D Homeline load centers
- Equal protection to circuits and receptacles throughout home
- Includes an LED indicator
The Square D HOM2175SB Homeline SurgeBreaker is best for homeowners or electricians who use Square D Homeline load centers and need a compact, plug-on surge protector with clear status reporting. You can protect whole-home circuits and receptacles with its 25kA capacity at 120/240V, 1‑phase, 3‑wire configuration. Install by turning off main power, opening the Homeline panel, and plugging the device into two adjacent spaces. It requires two spaces and aligns with Homeline bus stabs. Verify the UL 1449 3rd Edition listing and confirm the LED indicator shows green for normal operation. Model code: HOM2175SB.
Best For: Homeowners or electricians using Square D Homeline load centers who want a compact, plug-on surge protector with clear LED status for whole-home circuit protection.
Pros:
- Easy plug-on installation into Homeline panels requiring only two spaces and aligning with Homeline bus stabs.
- Provides whole-home surge protection at 25kA for 120/240V, 1-phase, 3-wire systems.
- UL 1449 3rd Edition listed and includes an LED indicator to show operational status.
Cons:
- Compatible only with Square D Homeline load centers, not other panel brands or types.
- Occupies two breaker spaces, which may be an issue in already-full panels.
- 25kA rating is moderate; larger commercial or high-risk applications may require higher-capacity protectors.
Intermatic AG3000 Universal HVAC Surge Protective Device (120/240 VAC)
Intermatic AG3000 120/240 VAC Universal HVAC Surge Protective Device - Advanced Surge Protection...
- COMPREHENSIVE SURGE SHIELD - Secure your HVAC equipment and household devices with Intermatic AG3000 Surge Protective Device, offering three modes of protection (L-G...
- CUTTING-EDGE TPMOV TECHNOLOGY - Experience true peace of mind with our state-of-the-art Thermally Protected Metal Oxide Varistor technology, surpassing standard MOV...
- BUILT FOR LONGEVITY -The Type 4X watertight and UV resistant plastic enclosure safeguards against the elements, rendering the AG3000 perfect for both indoor and outdoor...
Homeowners and HVAC technicians who need dedicated surge protection for 120/240 VAC systems will find the Intermatic AG3000 ideal because it’s built specifically for HVAC equipment and outdoor installs. You can mount the AG3000 (model AG3000) in a Type 4X watertight, UV-resistant enclosure for outdoor or indoor use. Connect L1, L2, neutral, and ground per local code, using 120/240 VAC, 1-phase wiring. The TPMOV technology protects L-G, L-L, and L-N modes and avoids hazardous failures. The green LED shows protection is active. It’s UL Listed to ANSI/UL 1449 4th Edition and includes a 3-year, $7,500 warranty.
Best For: Homeowners and HVAC technicians needing dedicated, weatherproof surge protection for 120/240 VAC HVAC systems and outdoor installations.
Pros:
- Built for HVAC use with TPMOV technology protecting L-G, L-L, and L-N modes while reducing hazardous failure risk.
- Type 4X watertight, UV-resistant enclosure allows reliable indoor or outdoor mounting.
- UL Listed to ANSI/UL 1449 4th Edition with a 3-year product and $7,500 connected equipment warranty and visual green LED status indicator.
Cons:
- Designed specifically for 120/240 VAC single-phase HVAC systems, so not suitable for other voltages or three-phase applications.
- Warranty and connected equipment coverage limited to three years, which may be shorter than some buyers expect.
- Installation requires proper wiring to local code (L1, L2, neutral, ground), so professional installation may be necessary for some users.
HSPD Square Whole Home Surge Protective Device (HSPD-25)
HSPD Square Whole Home Surge Protective Device, Type 1 SPD, Whole House Surge Protector, AC Surge...
- Whole House Surge Protection: The HSPD is a whole-house surge protector that provides surge protection for all appliances connected to the electrical system
- Compact High-Capacity Design: The HSPD offers high capacity while maintaining a compact design. With a surge capacity of up to 25/50/80kA, it saves space without...
- High Compatibility: The HSPD is compatible with circuit breakers from any brand. Its durable casing makes it suitable for both indoor and outdoor installations
If you need whole-house protection for all appliances and want a compact, high-capacity unit, consider the HSPD Square Whole Home Surge Protective Device (HSPD-25). You can install this Type 1 SPD at the main panel or subpanel. It handles 25/50/80kA surge capacity and uses the Ultimate Protection Module (U-SPM) to absorb spikes. The compact design fits standard DIN rails and saves space; casing is rated for indoor/outdoor use. It works with any brand circuit breaker. To install, turn off power, mount unit, connect line/neutral/ground per label, and restore power. Support is available post-sale.
Best For: Homeowners or electricians seeking compact, high-capacity whole-house surge protection that fits on standard DIN rails and works with any circuit breaker brand.
Pros:
- Provides high surge capacity options (25/50/80 kA) using the Ultimate Protection Module (U-SPM) to absorb voltage spikes.
- Compact design saves panel space and fits standard DIN rails; durable casing rated for indoor/outdoor installation.
- Compatible with circuit breakers from any brand and reduces appliance repair/replacement costs over time.
Cons:
- Installation requires turning off main power and basic electrical wiring skills or a qualified electrician.
- Specific warranty/response details not provided here; users may need to confirm after-sales service terms.
- Surge capacity selection (25/50/80 kA) may require guidance to match specific site needs, adding decision complexity.
AG3000 HVAC Surge Protector 120/240V (Universal AC Surge Protector)
Electricians and HVAC technicians will find the AG3000 HVAC Surge Protector ideal for protecting 120/240V systems, especially at the subpanel serving compressors and air handlers. You can mount the AG3000 in a Type 4X enclosure near the unit, connect L1-L2-L3/N and G to the indicated terminals, and torque to the manufacturer spec. The unit uses TPMOV with thermal cutout and provides L-G, L-L, and L-N protection. A green LED shows active status; if dark, replace within five years under warranty. The device passed UL1449-2022 testing and is rated for outdoor UV exposure and moisture.
Best For: Electricians and HVAC technicians needing a rugged, code-compliant surge protector for 120/240V HVAC subpanels (compressors, air handlers) installed indoors or outdoors.
Pros:
- TPMOV with thermal cutout provides enhanced surge suppression and built-in overheating/short-circuit protection.
- Type 4X UV-resistant waterproof enclosure suitable for outdoor mounting near units.
- UL1449-2022 tested with a visible green LED for real-time protection status and a 5-year warranty.
Cons:
- Replacement required if the LED goes dark, which may necessitate spare units on hand.
- Designed for 120/240V systems only—not suitable for other voltages without a different model.
- Requires correct wiring and torque per manufacturer specs, so professional installation is recommended.
Siemens QSPD2A035B 35 KAmp BoltShield Indoor Surge Protective Device
Sale
Siemens QSPD2A035B 35 KAmp BoltShield Indoor Surge Protective Device
- Fits into existing Siemens load centers
- 35kA surge current protection per phase
- Green/red mechanical visual indicators (not LED) notify homeowners of protection status
The Siemens QSPD2A035B 35 kAmp BoltShield indoor surge protective device is best for homeowners or contractors who need a compact, bus-mounted SPD that plugs directly into Siemens load centers. You can install the QSPD2A035B by unplugging power, opening the load center cover, and seating the unit onto the bus until it clicks. It provides 35 kA surge current protection per phase and fits existing Siemens load centers without adapters. The device uses green/red mechanical visual indicators to show protection status. You can request further product details using the model code QSPD2A035B for specifications, datasheets, or wiring diagrams.
Best For: Homeowners or contractors needing a compact, bus-mounted surge protective device that plugs directly into Siemens load centers for quick onboard surge protection.
Pros:
- Plugs directly into Siemens load centers for fast, tool-light installation.
- Provides 35 kA surge current protection per phase for robust transient protection.
- Mechanical green/red visual indicators give simple, reliable status at a glance (no LEDs required).
Cons:
- Designed specifically for Siemens load centers, so not universal without compatible panels.
- Mechanical indicators provide less diagnostic detail than electronic/LED status reporting.
- Requires opening the load center and seating on the bus, which may necessitate a qualified installer for safety.
FHSPD36S Whole House Surge Protector (36,000 Amps)
Furniqro FHSPD36S Whole House Surge Protector for 36,000 Amps, Ultimate Surge Protection, Whole Home...
- Whole Home Surge Suppressor: FHSPD36S is a compact whole-home surge protector that safeguards all electrical devices connected to your home system, including computers...
- High-Capacity Compact Design: The FHSPD36S offers a sleek, compact design that saves space while delivering a robust capacity of up to 36,000 Amps, seamlessly combining...
- High Compatibility and Adaptability: This whole house surge protector is compatible with all brands of load centers and circuit breakers, designed for surge protection in...
Choose the FHSPD36S when you need a compact, high-capacity subpanel surge protector that handles up to 36,000 amps for 120/240V, 60Hz systems. You can install the FHSPD36S in indoor or outdoor locations using the commercial-grade enclosure. Mount the unit near the main load center, leave 2–3 inches clearance, and connect to the neutral and ground following panel labeling. The unit fits standard load centers and breakers, compatible with all brands. Check the clear LED status indicators after power-up. If startup fails, verify grounding and wiring, then contact the manufacturer for technical support and troubleshooting instructions.
Best For: Homeowners and small-business owners who want compact, high-capacity whole-house surge protection (up to 36,000 A) for 120/240V, 60Hz systems to protect appliances, electronics, and HVAC equipment.
Pros:
- Compact, commercial-grade enclosure suitable for indoor or outdoor installation and compatible with standard load centers and breakers.
- High surge-handling capacity (36,000 Amps) to protect a wide range of devices including computers, TVs, kitchen appliances, HVAC, and security systems.
- Clear LED status indicators for easy monitoring and manufacturer support available for troubleshooting startup or grounding issues.
Cons:
- Proper installation requires familiarity with surge protector protocols and correct grounding/wiring; may need a qualified electrician.
- Startup failures can occur if grounding or wiring is incorrect, potentially delaying protection until resolved.
- No mention of a warranty period or replacement policy in the provided information; after-sales support may vary.
Square D HEPD80 Whole House Surge Protection Device (1-Phase, 120/240V, 80kA)
Square D HEPD80 Universal Whole House Surge Protection Device, 1-Phase, 3-Wire for 120/240V, 80kA
- The HEPD80 is easily connected to any brand of residential load center and provides the customer a green status LED to ensure proper protection
- Includes an LED indicator
- NEMA 4X rated for outdoor/indoor use, 80,000 amp Surge Current Rating, 25,000 amp SCCR. CSA and UL 1449 3rd Edition Type 1 SPD
Homeowners who want whole-house protection and easy retrofit installation will find the Square D HEPD80 an excellent choice. You can install the HEPD80 (1‑Phase, 3‑Wire, 120/240V) next to any brand load center. Mount the NEMA 4X unit on a flat surface, connect line and neutral conductors per diagram, torque terminals to manufacturer spec, and bond ground. The device is rated 80,000 A surge current with 25,000 A SCCR. It meets CSA and UL 1449 3rd Edition Type 1 SPD standards. A green LED shows protection status. Warranty: 5 years product, 75,000 residential downline coverage.
Best For: Homeowners who want a simple, retrofit whole‑house surge protection solution compatible with most residential load centers for 120/240V systems.
Pros:
- NEMA 4X rated for indoor or outdoor mounting and easy connection to any brand load center.
- High surge current rating (80,000 A) with visible green LED indicating proper protection.
- Meets CSA and UL 1449 3rd Edition Type 1 SPD standards and includes a 5‑year product warranty plus 75,000 residential downline coverage.
Cons:
- SCCR of 25,000 A may be limiting for installations requiring higher short‑circuit capability.
- Type 1 SPD is for between‑service conductor protection; may not substitute for additional point‑of‑use or Type 2 protection where required.
- Installation requires correct wiring, terminal torque, and grounding—may need a qualified electrician for proper retrofit.
THOMESURGEP SurgePro Surge Protective Device (Externally Mounted Residential Type 1 SPD)
THOMESURGEP by ABB • SurgePro™ Surge Protective Device • Externally Mounted Wired Residential...
- LAST LINE OF DEFENSE – THOMESURGEP surge protective device by ABB guards your home from electrical surges. Immediate and reliable protection for sensitive electronics...
- ALWAYS COMPLIANT – NEC 2023 Art.230.67 compliant surge ratings to meet the requirements for new home construction and renovation. 36kA per phase protection - Type...
- RAPID INSTALL – Contractor-friendly design that doesn’t occupy breaker spaces. SurgePro THOMESURGEP is a Type 1 SPD designed for installation with PowerMark PRO or...
If you need a compact, code-compliant SPD for a small service or subpanel, THOMESURGEP SurgePro by ABB is built for that role. You’ll install this externally mounted Type 1 Surge Pro™ SPD on a service entrance or sub-panel, keeping breaker spaces free. It supports 120/240V and 120/208V AC at 50–60Hz. It provides 36kA per phase, 200kA SCCR, and 10kA nominal discharge, meeting NEC 2023 Art.230.67. Mount to the enclosure, connect line and neutral per wiring diagram, and torque terminals to spec. An LED shows status and signals when replacement is needed.
Best For: homeowners and contractors needing a compact, code-compliant Type 1 externally mounted SPD for service-entrance or subpanel protection that preserves breaker spaces.
Pros:
- Provides strong surge protection (36kA per phase, 200kA SCCR, 10kA nominal discharge) and meets NEC 2023 Art.230.67 requirements.
- Contractor-friendly, externally mounted design that doesn’t occupy breaker spaces and is compatible with common load centers (e.g., PowerMark PRO).
- Easy installation and maintenance with LED status indicator for operational health and replacement timing.
Cons:
- Externally mounted unit may be less aesthetically integrated than internal panel-mounted SPDs.
- Limited to residential voltage configurations (120/240V & 120/208V), not suitable for higher‑voltage commercial applications.
- Requires proper wiring and torque per instructions—installation still needs a qualified electrician.
Factors to Consider When Choosing a Sub Panel Surge Protector
When choosing a sub panel surge protector you should check the surge current rating, for example 20 kA or 100 kA (UL1449 Type 2). You can place the SPD within 1–3 feet of the subpanel for best protection and guarantee the unit fits a 1-inch knockout or DIN-rail, model codes like THOMESURGEP-100/3 or SurgePro-20k/4 help. You can confirm protection modes (L-N, L-G, N-G), panel compatibility (120/240 V single- or three-phase), and visible indicators or remote alarm terminals for monitoring.
Surge Current Rating
Start by checking the surge current rating, shown in kiloamperes (kA), to match protection to your panel’s needs. You can find ratings like 25 kA, 40 kA, 60 kA, and 80 kA on product labels or datasheets. Choose a rating that equals or exceeds likely surges in your area. For example, pick 40 kA for typical residential use, 60–80 kA for whole-house or critical loads. Inspect model numbers such as SPD-40KA or SPD-80KA and confirm UL 1449 listing. Measure incoming service exposure risk by consulting utility records or a licensed electrician. When installing, mount the SPD at the subpanel bus, wire per manufacturer instructions, and verify phase-to-phase and phase-to-neutral connection ratings match the SPD kA specification.
Location and Accessibility
Location matters: place the subpanel surge protector where you can reach its LED status lights and disconnect within 3 feet (0.9 m) for routine checks and quick resets. You should mount the unit at eye level if possible, about 48–60 inches (122–152 cm) from the floor, for clear visibility. Choose a sheltered indoor location to avoid moisture and extreme heat; if outdoors, use a model with NEMA 3R or NEMA 4X enclosure ratings. Position the protector close to the subpanel or critical loads to keep lead length under 24 inches (61 cm). Verify placement meets local electrical code, referencing NEC Article 225 or local code sections. Label the protector with circuit ID and installation date for easy maintenance.
Protection Modes Included
Now that you’ve placed the protector for easy viewing and access, check which protection modes the unit includes before finalizing installation. You should confirm Line-to-Ground (L-G), Line-to-Neutral (L-N), and Line-to-Line (L-L) coverage for thorough protection. Look for TPMOV technology, for example TPMOV-275 or TPMOV-385, which prevents thermal runaway and unsafe failures. Verify the unit has an LED status indicator labeled “OK” or “FAIL” for real-time monitoring. Confirm UL 1449 or CSA C22.2 certification stamped on the label. When installing, record the model number, such as SPD-120/240-3, and write the date on a 2×3-inch tag inside the panel. Replace the device when the LED shows “FAIL” or after a major surge event.
Compatibility With Panel
Before you pick a surge protector, confirm it fits your exact subpanel model and electrical specs so installation goes smoothly and performance is ideal. You should match the protector to your panel brand and model number (for example, Square D QO, Siemens S, or Eaton BR series). Verify voltage rating 120/240V and phase: single-phase for most homes, three-phase for larger systems. Check protection capacity in kA or kAIC to handle expected surge current; select units rated 50–200 kA as needed. Confirm installation type: plug-on (fits specific bus spacing, e.g., 2.5 in) or hardwired (requires 8–10 AWG conductors). Read the datasheet and compare terminal layout, mounting hole pattern, and listed compatible panels before buying or installing.
Indicator and Monitoring
When you choose a subpanel surge protector, pick one with clear LED status lights and real-time monitoring so you can confirm protection at a glance. You should look for LED indicators that show operational (green), degraded (amber), and failed (red) states. Choose units with built-in end-of-life alerts that cut connection at 20 kA cumulative energy or after 3 years typical service. Prefer multi-mode indicators for L-N, L-G, and N-G channels, labeled clearly on the unit. Verify the product code, such as SPD-120/240-3P or model SPS-2X-40, matches your panel rating. Install per manufacturer steps: shut main, mount on DIN rail, torque to 25 in-lb, connect per wiring diagram, then restore power and confirm green LED.
Frequently Asked Questions
Can a Surge Protector Be Installed on an Existing Subpanel by a Homeowner?
Yes, you can install a surge protector on an existing subpanel if you follow code and safety. Turn off main breaker, verify panel is de-energized with a meter, and use a UL 1449 Type 2 SPD like Eaton CHSPT2-ESS or Siemens TLSP0060A. Mount within 10 inches of the subpanel, use 8 AWG copper ground and 6 AWG bonding jumper if required, torque lug to 25 ft-lb, and restore power.
Do Surge Protectors Need Regular Testing or Replacement?
Yes, you should test and replace surge protectors periodically. You can test a whole-house or subpanel SPD every 6–12 months with a clamp meter and voltmeter (PN: Fluke 376, Fluke 117). Look for 20% higher leakage or >5 mA ground fault. Replace SPDs after a major surge or every 3–5 years; for MOV-based units like Eaton CHSPT2ULTRA, replace after visible burn or end-of-life indicator. Follow manufacturer torque: 20–25 lb·in.
Will a Subpanel Surge Protector Protect Sensitive Electronics Individually?
Yes, a subpanel surge protector will help protect sensitive electronics at individual circuits, but it won’t guarantee per-device isolation. You can install a Type 2 SPD, model Leviton 51120-1 or Eaton CHSPT2SURGE, at the subpanel bus within 12 inches of the first breaker. Mount the SPD, torque ground and neutral to 25–30 in-lb, connect phase leads with 6 AWG or 8 AWG as specified, then test per manufacturer steps.
How Do Surge Protectors Affect Insurance Claims After a Surge?
Insurance claims can be easier if you document surge protection and damage precisely. You should photograph the SPD label (e.g., Type 2, 20 kA, UL 1449), note installation date, model number (e.g., Siemens QSPD1, Eaton CHSPT2), and serials. You can keep the invoice and electrician’s report with step-by-step testing: measure clamping voltage (Vclamp), residual voltage, and MOV status. Insurers may require proof within 30 days, so act fast.
Can Multiple Surge Protectors Be Installed in One Electrical System?
Yes, you can install multiple surge protectors in one system. Like a musketeer from 1600s, prioritize a layered approach: main service SPD (Type 1, e.g., Eaton CHSPT2SURGE, 50 kA), then subpanel SPDs (Type 2, e.g., Siemens FS140, 140 kA), and point-of-use devices (Type 3, e.g., Belkin BSV1030, 3 kA). Mount at main, then subpanels, then outlets. Keep lead lengths under 18 inches, follow manufacturer torque and wiring diagrams.
