Product Overview:
Commercial HVAC systems that use pneumatic controls rely on room thermostats to convert changes in space temperature into air-pressure signals for connected equipment. The Johnson Controls T-4100-2 Pneumatic Thermostat is an OEM, single-temperature room control designed for reverse-acting operation in compatible pneumatic HVAC applications. Its vertical wall-mount configuration includes a cover, Fahrenheit temperature scale, and manual setpoint adjustment for controlling room temperature in commercial heating and cooling systems.
Pneumatic Temperature Regulation:
The thermostat uses a bimetallic sensing element to respond to changes in surrounding room temperature. As the sensed temperature changes in relation to the selected setpoint, the internal mechanism adjusts the pneumatic output pressure. Its reverse-acting operation causes output pressure to decrease as room temperature increases. This proportional pressure response provides a control signal for connected pneumatic devices.
Air Pressure Control:
The uses a low-volume, single-pipe pneumatic arrangement with one air connection for its restricted supply and output. A remote restrictor provides the required restricted air supply, while the thermostat regulates the resulting output pressure in response to room temperature. Its adjustable sensitivity allows the pressure response to be adjusted for the requirements of the connected control application.
Replacement Guidelines:
Replacement of the Johnson Controls T-4100-2 may be necessary when the thermostat can no longer maintain dependable room-temperature control, its pneumatic output becomes unreliable, or its internal sensing mechanism fails to respond consistently to temperature changes. Physical deterioration or damage that affects normal thermostat operation may also indicate the need for replacement.
Common Failure Symptoms:
- Room temperature remains consistently above or below the selected setpoint.
- Pneumatic output pressure fluctuates unexpectedly during normal operation.
- Thermostat adjustment produces little or no change in control response.
- Temperature control becomes noticeably inconsistent between operating cycles.
- Thermostat produces an unstable response to gradual room-temperature changes.
Equipment Compatibility:
The Johnson Controls T-4100-2 is an pneumatic thermostat intended for OEM compatible one-pipe, low-volume pneumatic HVAC systems requiring reverse-acting operation. Its vertical mounting configuration and Fahrenheit temperature scale are specific characteristics of this model. The T-4100 series includes models with different operating actions and temperature scales, so compatibility should not be assumed across the series. Confirm the complete model designation and the equipment manufacturer's documented application requirements before purchasing.
Technical Specifications:
Brand: Johnson Controls
Part Number: T-4100-2
Component Type: Pneumatic Room Thermostat
Operating Action: Reverse Acting
Pneumatic Arrangement: Single-Pipe, Low-Volume
Mounting Type: Vertical Wall Mount
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