Description
The Johnson Controls A19AAF-12 is a mechanical remote bulb temperature control engineered for reliable, precise temperature sensing and switching across a broad range of HVAC and refrigeration applications. With its wide voltage compatibility and robust construction, this control is a trusted solution for OEM equipment builders and commercial HVAC service professionals alike.
Overview
The A19AAF-12 uses a vapor-pressure sensing bulb connected via a flexible capillary tube to monitor ambient or fluid temperatures and actuate a single-pole, double-throw (SPDT) switch. The automatic reset feature ensures the control returns to its normal operating state once the temperature moves back within range — no manual intervention required.
Key Features
- Wide voltage range: 24 to 277Vac for versatile system compatibility
- SPDT switching action for flexible control circuit wiring
- Automatic reset — no manual reset required after actuation
- Setpoint range: 25°F to 225°F for broad application coverage
- Fixed differential: 3.5°F for consistent, repeatable switching
- 10-foot capillary length for remote sensing flexibility
- 3/8″ x 3″ sensing bulb for accurate temperature measurement
- Screwdriver-adjustable setpoint for easy field calibration
- Mechanical (non-electronic) design for dependable, long-term operation
Specifications
- Brand: Johnson Controls
- SKU / Model: A19AAF-12
- Control Type: Mechanical Remote Bulb Temperature Control
- Voltage: 24 to 277Vac
- Switch Action: SPDT (Single-Pole, Double-Throw)
- Reset Type: Automatic
- Setpoint Range: 25°F to 225°F
- Fixed Differential: 3.5°F
- Capillary Length: 10 feet
- Sensing Bulb Size: 3/8″ diameter x 3″ length
- Setpoint Adjustment: Screwdriver
Typical Applications
- Commercial HVAC unit temperature control
- Refrigeration equipment temperature regulation
- Fan cycling and freeze protection
- OEM equipment integration requiring remote sensing
- Industrial process temperature switching







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