SP24AA — 24VAC Single-Pair Low-Voltage Surge Protector (Series / Inline) with Equipment Ground Connection
$79.00
SP24AA is a 24VAC single-pair low-voltage control circuits (HVAC, thermostats, doorbells, and fire/secuiry/alarm loops). surge protector for inline (series) installation on control and signaling circuits. Protects one circuit through Terminal A and Terminal B and uses a green equipment ground lead.
24 VAC circuits only — verify voltage before installation.
Specifications (SP24AA)
Device type: Low-voltage surge protective device (SPD), series / inline installation
Circuit pair protected: Single pair (Terminal A & Terminal B)
- Nominal operating voltage: 24 VAC
MCOV (Maximum Continuous Operating Voltage): 33 V
Clamping voltage: 39 V
Maximum continuous current: 5 A
Surge current rating: 2.5 kA
Protection modes: Differential (line-to-line) and Common mode (line-to-ground)
Terminal wire range: 30–14 AWG
Operating temperature: −35°C to +70°C (−31°F to +158°F)
Recommended spacing to protected equipment: ≥ 18 inches
Ground: Green lead provided; connect to equipment ground
Serviceability: Sealed / non-serviceable; no user-serviceable parts (do not Hi-Pot test)
The Bad Wolf SP24AA is a 24VAC single-pair low-voltage surge protector designed for inline (series) installation on control and signaling circuits. It protects one 24VAC circuit through Terminal A and Terminal B and uses the green equipment ground lead to help manage common-mode surges. SP24AA helps protect sensitive low-voltage equipment from transient overvoltage events caused by nearby lightning, utility switching, and inductive load switching.
Where it’s used
SP24AA is commonly installed on 24VAC control power and low-voltage signaling circuits, including:
HVAC control circuits and thermostats
Air handler/furnace control boards
Doorbell and smart doorbell transformers
Security/CCTV power or control loops
Fire/security low-voltage loops and other control wiring
- Helps protect control boards, transformers, relays, and connected low-voltage devices from transient surges.
Installation notes (important)
Series (inline) install required: the SP24AA is installed in line with the circuit being protected.
Bidirectional: either side can be used as IN/OUT.
- Maintain continuity: connect A→A and B→B through the SPD.
Ground connection: Connect the green ground lead to a proper equipment ground for best performance.
Maintain at least 18 inches between the SPD and the equipment being protected.
Verify the circuit is 24 VAC before installation and install per applicable electrical codes by a qualified professional.
Status and service
The SP24AA is sealed and non-serviceable. There are no user-serviceable parts. Do not Hi-Pot test the device, as this may damage the SPD.
Product Details
| Weight | 5 oz |
|---|---|
| Dimensions | 5.125 × 3.25 × 1.25 in |
| Continuous Current Rating | 5 |
| Environmental Rating | Indoor |
| Type of Electrical Current | AC |
| Voltage (Vac) | 24 |
| Application | Doorbell, HVAC, Thermostat |
Installation
Professional installation is recommended. Installation should be performed by a qualified, licensed professional in accordance with the product instructions, applicable electrical codes, and local requirements.
Always turn off power to the circuit and connected equipment before installation. Verify that power has been disabled using an appropriate voltage sensing device before working on the circuit.
24VAC Inline Installation Notes
- The SP24AA is designed for compatible 24VAC low-voltage control and signaling circuits only.
- Verify that the circuit is 24VAC before installation.
- Mount the surge protector securely in an accessible location.
- For best performance, keep wiring runs short and neat.
- The SP24AA is installed inline, or in series, with the circuit being protected.
- Cut the two conductors and route them through the surge protector so the device is in line with the protected circuit.
- Maintain continuity through the surge protector by connecting A to A and B to B.
- The unit is bidirectional, so either side may be used as the input or output side.
- Connect the green ground lead to a solid equipment grounding point. A low-impedance ground connection is critical for surge protection performance.
- Maintain at least 18 inches of wire between the surge protector and the protected equipment.
Typical Applications
- HVAC control circuits and thermostats
- Air handler and furnace control boards
- Doorbell and smart doorbell transformers
- Security or CCTV power and control loops
- Fire, security, and other low-voltage control wiring
Final Check
Before restoring power, inspect all terminations for tightness and correct wiring. Verify A-to-A and B-to-B continuity, confirm the green ground lead is securely connected to equipment ground, and make sure all conductors are properly seated.
After installation is complete, restore power and verify normal equipment operation.
Service and Warranty Note
This product contains no user-serviceable parts. Do not open or tamper with the device. Tampering with the product may void the warranty.
Refer to the SP24AA installation instructions for complete wiring, spacing, grounding, troubleshooting, and product-specific installation requirements.
Warranty
Bad Wolf surge protection devices include a 5-year product warranty.
Eligible products may also include connected equipment warranty coverage when properly installed and registered according to the warranty terms.
Please review the full warranty terms for complete details, limitations, registration requirements, and coverage information.
FAQ
What is the SP24AA mainly used for?
The SP24AA is used to help protect single-pair, two-wire 24VAC low-voltage circuits from damaging overvoltage and surge events. Common applications include HVAC thermostat circuits, HVAC transformer secondary circuits, doorbell transformer circuits, access control, gate operators, security/alarm circuits, fire alarm/control circuits, and other compatible 24VAC control or signaling circuits.
What voltage is the SP24AA designed for?
The SP24AA is designed for 24VAC circuits only. It should not be used on DC circuits or AC circuits above 24 volts.
What does the 2.5KA rating mean?
The 2.5KA rating refers to the surge current capacity of the device. The SP24AA is designed to help protect compatible 24VAC circuits from damaging surge and overvoltage events when properly installed.
What type of circuits can the SP24AA protect?
The SP24AA is designed for one single-pair, two-wire 24VAC circuit. It has two input wire connections and two output wire connections.
Can the SP24AA be used on HVAC thermostat circuits?
Yes. The SP24AA is a good option for compatible 24VAC HVAC thermostat circuits, HVAC transformer secondary circuits, and related low-voltage control wiring.
Can the SP24AA be used on doorbell transformer circuits?
Yes. The SP24AA may be used on compatible 24VAC doorbell transformer circuits where the voltage and wiring match the product specifications.
Can the SP24AA be used for access control, gate operators, or security circuits?
Yes. The SP24AA may be used on compatible 24VAC access control, gate operator, security, alarm, and low-voltage control circuits that match the product ratings.
How is the SP24AA different from the SP24A24AA?
The SP24AA is designed for one single-pair, two-wire 24VAC circuit. The SP24A24AA is designed for two-pair or four-wire 24VAC applications, such as two separate two-wire circuits or one four-wire circuit.
How is the SP24AA wired?
The SP24AA uses screw terminals and is installed inline between the 24VAC source and the protected load. For example, it may be installed between a 24VAC transformer and the thermostat, control board, doorbell circuit, or other compatible low-voltage device being protected.
Does the SP24AA connect to ground?
The SP24AA includes an optional ground wire pigtail. The ground connection may be used when appropriate for the installation and system design.
Where should the SP24AA be installed?
The SP24AA is commonly installed near the transformer, control board, thermostat wiring, doorbell transformer, control panel, equipment being protected, building entry point, outdoor equipment connection, or another location where surge protection is needed on a compatible 24VAC circuit.
Does the SP24AA have status lights?
No. The SP24AA does not have status indicator lights.
Can the SP24AA be installed outdoors?
The SP24AA is intended for indoor installation only. If used near outdoor equipment, it should be installed in a suitable protected indoor or enclosed location according to the product instructions and applicable requirements.
Does the SP24AA provide short circuit or overcurrent protection?
No. The SP24AA provides overvoltage and surge protection only. It does not provide short circuit or overcurrent protection. The protected circuit should have appropriate circuit protection as required for the system.
Can the SP24AA be used on DC circuits?
No. The SP24AA is designed for 24VAC circuits only and should not be used on DC applications.
Can the SP24AA be used on 120VAC or higher-voltage AC circuits?
No. The SP24AA should not be used on 120VAC circuits or any AC circuit above 24 volts. Using the device outside its rating can create an unsafe condition and damage the product or connected equipment.
Who should install this product?
This product should be installed by a qualified technician, electrician, low-voltage installer, HVAC contractor, fire alarm technician, security technician, doorbell installer, or other qualified person familiar with the circuit and equipment being protected.
Does this product include a warranty?
Bad Wolf surge protection devices include a 5-year product warranty. Eligible products may also include connected equipment warranty coverage when properly installed and registered according to the warranty terms.
Specifications
SP24AA Specifications
| Model Number | SP24AA |
|---|---|
| Product Type | 24VAC single-pair low-voltage surge protector |
| Device Type | Low-voltage SPD, series / inline installation |
| Application | 24VAC control, signaling, and low-voltage equipment circuits |
| Circuit Protected | Single pair through Terminal A and Terminal B |
| Nominal Operating Voltage | 24VAC |
| MCOV | 33V |
| Clamping Voltage | 39V |
| Maximum Continuous Current | 5A |
| Surge Current Rating | 2.5kA |
| Protection Modes | Differential mode, line-to-line, and common mode, line-to-ground |
| Terminal Wire Range | 30–14 AWG |
| Operating Temperature | -31°F to +158°F (-35°C to +70°C) |
| Recommended Spacing to Protected Equipment | Minimum 18 inches |
| Ground Connection | Green ground lead provided; connect to equipment ground |
| Installation Direction | Bidirectional; either side may be used as IN or OUT |
| Serviceability | No user-serviceable parts |
Wiring Notes
- The SP24AA protects one pair of conductors through Terminal A and Terminal B.
- Maintain continuity through the device by connecting A to A and B to B.
- The unit is bidirectional, so either side may be used as the input or output side.
- Connect the green ground lead to equipment ground.
- Maintain at least 18 inches of wire between the surge protector and the protected equipment.
Specifications are subject to change. Refer to the product label and installation instructions for complete product-specific ratings and installation requirements.