You’ll want a UL‑listed, TPMOV‑based or Type‑1 120/240V SPD mounted at the disconnect to protect your AC compressor and control board; top picks in 2026 include the Intermatic AG3000 (Type 4X, full L‑G/L‑L/L‑N), Mars 83905 (compact TPMOV, LED), the ONTISIV AG3000 model, DITEK DTK‑120/240CM+ (NEMA 4X, 2W+G) and WeCooper 120/240VAC (25 kA, IP66). Keep an eye on warranty, enclosure rating and surge kA for best protection—more details follow.
| Intermatic AG3000 HVAC Surge Protective Device (120/240VAC) |  | Best Overall | Voltage Rating: 120/240 VAC | Enclosure Weatherproofing: Type 4X watertight, UV‑resistant plastic | MOV-based Surge Technology: Thermally Protected MOV (TPMOV) | VIEW LATEST PRICE | Read Our Analysis |
| Mars 83905 HVAC Surge Protective Device |  | Best Seller | Voltage Rating: (HVAC unit compatible) 120/240 VAC | Enclosure Weatherproofing: Weatherproof enclosure (suitable for outdoor) | MOV-based Surge Technology: Thermally protected MOV (TPMOV) | VIEW LATEST PRICE | Read Our Analysis |
| HVAC AC Surge Protector for AG3000 (120/240V) |  | Budget-Friendly Pick | Voltage Rating: 120/240 V (120 VAC noted for plug compatibility) | Enclosure Weatherproofing: Type 4X watertight, UV‑resistant plastic | MOV-based Surge Technology: Advanced thermally protected MOVs | VIEW LATEST PRICE | Read Our Analysis |
| DITEK DTK-120/240CM+ Surge Protector NEMA 4X UL1449 |  | Compact & Reliable | Voltage Rating: 120/240 VAC | Enclosure Weatherproofing: NEMA 4X | MOV-based Surge Technology: (UL1449 listed parallel protector typically uses MOVs) — UL1449-listed SPD design (implicit MOV-based technology) | VIEW LATEST PRICE | Read Our Analysis |
| WeCooper HVAC 120/240VAC Type 1 Surge Protector |  | Heavy-Duty Protection | Voltage Rating: 120/240 VAC (L-L 240 VAC, L-G 120 VAC) | Enclosure Weatherproofing: IP66 dustproof/water‑jet resistant, UV‑resistant | MOV-based Surge Technology: Timed‑Fuse Metal Oxide Varistor (TFMV / MOV) | VIEW LATEST PRICE | Read Our Analysis |
More Details on Our Top Picks
Intermatic AG3000 HVAC Surge Protective Device (120/240VAC)
If you need robust, weatherproof surge protection for a split- or packaged HVAC system, the Intermatic AG3000 is a strong choice — it uses thermally protected MOVs (TPMOV) and offers full 120/240 VAC, L‑G, L‑L and L‑N protection so you can confidently shield sensitive compressors and control boards from damaging transients. You’ll get UL Listed ANSI/UL 1449 5th Edition safety, a Type 4X watertight, UV‑resistant enclosure for indoor or outdoor use, and a green LED that shows protection status. Intermatic backs it with a 3‑year product and $7,500 connected equipment warranty for added peace of mind.
- Voltage Rating:120/240 VAC
- Enclosure Weatherproofing:Type 4X watertight, UV‑resistant plastic
- MOV-based Surge Technology:Thermally Protected MOV (TPMOV)
- Protection Modes (L-L / L-G / L-N):L‑G, L‑L, L‑N
- Visual Protection Indicator:Green LED protection/status indicator
- HVAC-specific / Designed for AC Units:Marketed as HVAC surge protective device for HVAC equipment
- Additional Feature:3-year product warranty
- Additional Feature:$7,500 connected warranty
- Additional Feature:Thermally protected MOVs
Mars 83905 HVAC Surge Protective Device
The Mars 83905 HVAC Surge Protective Device is your best choice if you want compact, weatherproof protection that safeguards compressors, ECM motors, and control boards with thermally protected MOV technology—easy to install on the unit and clear to monitor thanks to its LED protection indicator. You’ll get Type 1/2 compatibility without needing an extra overcurrent device, and the TPMOVs give thermal fail-safe protection for spikes and transients. It’s small and lightweight (8x8x4 in, 12 oz), rated highly by users (4.8/5 from 263 reviews), sold by Standard Plumbing Supply, and covered by typical warranty and Amazon return terms.
- Voltage Rating:(HVAC unit compatible) 120/240 VAC
- Enclosure Weatherproofing:Weatherproof enclosure (suitable for outdoor)
- MOV-based Surge Technology:Thermally protected MOV (TPMOV)
- Protection Modes (L-L / L-G / L-N):Protects HVAC lines (line/ground/line‑to‑line protection implied by HVAC SPD design)
- Visual Protection Indicator:LED protection indicator
- HVAC-specific / Designed for AC Units:Specifically for HVAC equipment (compressors, controls, ECM motors, etc.)
- Additional Feature:Weatherproof enclosure
- Additional Feature:Type 1/2 compatible
- Additional Feature:Easy installation
HVAC AC Surge Protector for AG3000 (120/240V)
Protect your AG3000 HVAC with the ONTISIV HVAC Surge Protector, built for homeowners and technicians who need reliable, compact surge defense for 120/240V systems. You’ll get a universal Type A (2-pin) unit rated 120V with one outlet, offering L-G, L-L and L-N protection via thermally protected MOVs that shut down if they overheat. A green LED shows protection status; the device’s factory testing adds confidence. The Type 4X watertight, UV-resistant enclosure mounts quickly to breaker panels or disconnects for indoor or outdoor use. ONTISIV backs it with a one-year warranty, vendor support, and a 30-day return option.
- Voltage Rating:120/240 V (120 VAC noted for plug compatibility)
- Enclosure Weatherproofing:Type 4X watertight, UV‑resistant plastic
- MOV-based Surge Technology:Advanced thermally protected MOVs
- Protection Modes (L-L / L-G / L-N):L‑G, L‑L, L‑N
- Visual Protection Indicator:Built‑in green LED protection/status indicator
- HVAC-specific / Designed for AC Units:Labeled as HVAC Surge Protector compatible with AG3000 HVAC systems
- Additional Feature:Type A power plug
- Additional Feature:Quick mount compatible
- Additional Feature:Factory tested
DITEK DTK-120/240CM+ Surge Protector NEMA 4X UL1449
Homeowners and HVAC techs who need a compact, weatherproof surge solution will appreciate the DITEK DTK-120/240CM+ for its NEMA 4X-rated enclosure and UL1449 listing, which keep sensitive 120/240VAC air-conditioning equipment protected against transient spikes. You’ll find a parallel, Type 1 SPD configured 2W(+G) to handle common-mode and line-to-line surges in a small 4 x 3 x 2-inch package weighing just over three ounces. With strong customer ratings (4.7/5 from 302 reviews) and continued availability, it’s a practical choice for outdoor or rooftop installs. Warranty support is available via DITEK customer service.
- Voltage Rating:120/240 VAC
- Enclosure Weatherproofing:NEMA 4X
- MOV-based Surge Technology:(UL1449 listed parallel protector typically uses MOVs) — UL1449-listed SPD design (implicit MOV-based technology)
- Protection Modes (L-L / L-G / L-N):2W(+G) configuration (provides line and ground protection for 120/240)
- Visual Protection Indicator:(Product listing includes UL1449 and customer feedback; typical unit includes status/indicator) — UL1449 listed with customer documentation (indicator implied for status)
- HVAC-specific / Designed for AC Units:Surge arrestor for 120/240VAC (used in HVAC/electrical distribution applications)
- Additional Feature:NEMA 4X rated
- Additional Feature:Compact dimensions
- Additional Feature:UL1449 listed
WeCooper HVAC 120/240VAC Type 1 Surge Protector
If you need a rugged, UL 1449-certified Type 1 surge protector for outdoor HVAC equipment, the WeCooper 120/240 VAC unit is a strong choice because it’s built for 1-phase, 3-wire systems and handles up to 25 kA of surge current. You’ll get Type 1 protection for air conditioners, heat pumps, mini-splits, condensers, and compressors with L-L 240 V / L-G 120 V ratings and 200 kA SCCR. The IP66, UV-resistant enclosure stands up to dust and strong water jets; a green LED shows protection status. Installation is quick, units are factory-tested, and support/warranty options are available.
- Voltage Rating:120/240 VAC (L-L 240 VAC, L-G 120 VAC)
- Enclosure Weatherproofing:IP66 dustproof/water‑jet resistant, UV‑resistant
- MOV-based Surge Technology:Timed‑Fuse Metal Oxide Varistor (TFMV / MOV)
- Protection Modes (L-L / L-G / L-N):L‑L 240 VAC, L‑G 120 VAC (3‑wire Type 1 SPD)
- Visual Protection Indicator:Green LED protection/status indicator
- HVAC-specific / Designed for AC Units:Universal HVAC surge protector for air conditioners, heat pumps, condensers, compressors
- Additional Feature:25 kA surge capacity
- Additional Feature:IP66-rated enclosure
- Additional Feature:200 kA SCCR
Factors to Consider When Choosing Surge Protectors for Ac Unit
When choosing a surge protector for your AC unit, check that its voltage and phase match your system and that its surge current rating can handle likely spikes. Pay attention to response time and the protective technology it uses, plus the enclosure rating and where you’ll mount it to ensure durability. Also confirm installation requirements and mounting options so you can fit it safely and compliantly.
Voltage And Phase Compatibility
Because surge protectors must match your AC system’s electrical characteristics, verify the unit’s nominal voltage and phase compatibility before buying. Confirm the SPD is rated for your system voltage (for example 120/240 VAC) so clamping levels and mode configuration (L‑L, L‑N, L‑G) align with the supply. Ensure the protector supports the same phase setup—single‑phase for most homes or three‑phase for commercial gear. Check the maximum continuous operating voltage (MCOV/Vc) is equal to or slightly above your line voltage to avoid nuisance conduction. Match the SPD’s connection type and modes (2‑wire, 3‑wire, multi‑mode) to your circuit wiring, including neutral and ground. For split‑phase 240V, pick an SPD specified for both line‑to‑line and line‑to‑ground protection.
Surge Current Rating
Start by checking the surge current rating—expressed in kiloamperes (kA)—because it tells you how much instantaneous current an SPD can divert away from your AC unit during a transient. You’ll want at least 20–40 kA per mode for typical HVAC exposure to lightning-induced or utility-switching surges. If your site sees frequent or large transients, consider 50–100 kA models for added headroom and longer service life, knowing size and cost rise. Verify whether manufacturers quote per-mode (L-L, L-G) or cumulative totals so you’re not misled by aggregate figures. Always weigh surge current rating against energy absorption (joules) and clamp/let-through voltage—higher kA with low let-through voltage gives better protection for sensitive AC electronics.
Response Time And Technology
Surge current rating tells you how much energy an SPD can handle, but you also need to know how quickly it acts and what technology it uses. You want devices that clamp in sub‑nanoseconds to nanoseconds so sensitive AC control electronics see minimal energy; TVS diodes act in picoseconds but handle lower energy, while MOVs offer nanosecond response with high energy capacity. Gas discharge tubes are slower (microseconds) yet useful for large, sustained surges. Prefer thermally‑protected MOVs or timed‑fuse MOV designs that provide near‑instantaneous clamping and then disconnect or de‑energize during prolonged overvoltage to avoid thermal runaway. Match low clamping and let‑through voltages with fast response, and choose coordinated thermal or fuse backup so you get instant suppression plus safe shutdown under repeated or extended surges.
Enclosure Rating And Location
When you pick a surge protector for an AC unit, match the enclosure rating and mounting location to the environment so the device actually lasts and functions when needed. Choose a NEMA/Type rating suited to the install: Type 1 for indoor panels, Type 4X/NEMA 4X or IP66 for outdoor, wet, or UV‑exposed locations. Use weatherproof, UV‑resistant housings on exterior condensing units and exposed disconnects to prevent moisture ingress and material degradation. Verify the enclosure is listed for the intended mounting point and permits wiring access without breaking the seal. Confirm adequate internal clearance and mechanical protection for components and terminals to keep dielectric integrity during surges. Prefer housings that retain visible status indicators so you can check protection without opening a sealed enclosure.
Installation And Mounting Options
Mount the surge protector as close as practical to the service entrance or HVAC disconnect—typically within 10–20 inches—to keep lead lengths short and minimize let‑through voltage, and use a dedicated conduit or wiring method with short, straight leads sized the same as the circuit conductors to maintain low impedance and meet code. You should install the device in a weatherproof NEMA/IP‑rated enclosure (or inside the panel if indoors) when the unit is outdoors, ensuring UV resistance and watertight seals. Mount it to a solid surface with clearance for ventilation and access to the LED/status indicator and terminals for testing. Follow manufacturer torque specs, bond the SPD to the system grounding conductor, and verify ground electrode continuity per NEC and local requirements.
Warranty And Connected Equipment Coverage
You’ve taken care to place and wire the SPD correctly; now check the protection that comes after installation: the warranty and any connected‑equipment coverage. Look at warranty length (commonly 1–3 years) and confirm it matches your expected equipment lifespan. Verify whether a connected‑equipment guarantee exists, its dollar limit and coverage period — often a few thousand dollars over 1–3 years. Read the fine print for voiding conditions: improper installation, missing surge‑event documentation, or failure to replace the SPD after loss of protection. Confirm the claims process: required documentation, proof of a surge, timelines, and whether onsite inspection or third‑party testing is mandatory. Prefer SPDs that explicitly cover both the protector and key HVAC components (compressor, control board, ECM).