Overview
The Honeywell AT88A1021 is a foot-mounted control power transformer engineered for HVAC systems, building automation, and industrial control applications. This 75VA transformer steps down 208/240V primary voltage to 24V secondary, providing stable, regulated power for thermostats, control boards, solenoids, and low-voltage pilot circuits. Built with internal fuse protection and overload safeguards, the AT88A1021 delivers dependable operation in both commercial and residential installations.
Key Features
- Internal Fuse Protection — Integrated circuit protection eliminates the need for external secondary-side fusing in most applications
- Overload Protection — Primary winding burnout protection extends component life under transient load conditions
- Color-Coded Leadwires — Clearly labeled primary and secondary connections streamline installation and reduce wiring errors
- Foot-Mounted Design — Compact footprint suitable for electrical boxes (4×4 in., octagonal) or direct mounting to junction boxes
- NEC Class 2 Compliance — Meets UL 1585 safety standards for both wet (Class 3) and dry (Class 2) installations
- 12-Inch Lead Wires — Pre-terminated connections on both primary and secondary sides simplify field installation
Technical Specifications
| Primary Voltage | 208/240V AC, 50/60 Hz |
| Secondary Voltage | 24V AC |
| Power Rating | 75 VA |
| Secondary Current | 3.13 A (at full load) |
| Circuit Protection | Internal Fuse (secondary side) |
| Mounting Type | Foot-Mounted |
| Primary Connection | 12-inch lead wires (color-coded) |
| Secondary Connection | 12-inch lead wires |
| Weight | 2.9 lbs |
| Certifications | UL 1585, NEC Class 2 & 3 |
| Series | AT88A (Tradeline) |
| Compatible Models | AT88A1013, AT88A1120 |
Typical Applications
- HVAC system control power and thermostat circuits
- Building automation and BMS (Building Management System) 24V supply rails
- Industrial control panels requiring isolated 24V DC or AC secondary power
- Solenoid valve and damper actuator power supplies
- Low-voltage relay and contactor pilot circuits
- Furnace and air-handling unit control transformers
Compatibility & Replacements
Compatible With
- HVAC control boards and thermostats rated for 24V AC input
- Industrial PLC and building automation controllers requiring Class 2 power
- Solenoid valves and pneumatic actuators (24V AC coils)
- Standard electrical boxes: 4×4 in., octagonal, and 2×4 in. boxes with knockouts
- Carrier, Bryant, Payne, York, Luxaire, and Coleman HVAC systems
Replaces / Drop-In Replacement For
- AT88A1013
- AT88A1120
- UPC: 085267036382
- Equivalent Honeywell AT88A series transformers rated 75VA, 208/240V primary, 24V secondary
Works With
- Standard 208/240V three-phase or single-phase mains power distribution
- Class 2 and Class 3 low-voltage control circuits per NEC Article 725
- Any 24V AC load not exceeding 75VA total (approximately 3.13 amperes secondary)
- NEMA and UL-listed control enclosures and junction boxes
