These thermostats are available in either direct- or reverse-acting models, each utilizing two bimetals, one heating and one cooling, to interrupt the deadband (branch) pressure. In the direct-acting model, the heating bimetal modulates the pressure between zero and the deadband pressure, and the cooling bimetal modulates the branch pressure between the deadband pressure and main air pressure. In the reverse-acting model, this action is reversed. The deadband pressure is adjustable in the field, to adapt to specific applications. Two concealed setpoint dials, one heating and one cooling, are used to set the individual heating and cooling setpoints to the desired values. This creates the desired deadband between the two selected setpoints. All calibration functions are accessible from the front of the thermostat. The use of a blank cover (21-928) is recommended with this device. Other cover options may be utilized if desired.
- Factory-calibrated, stainless steel ball-in-seat provides pneumatic feedback for stable, linear operation.
- Deadband is easily selected by setting the desired heating and cooling setpoints.
- Field-adjustable deadband output pressure is factory set at 8 psig.
- Leak-proof, self-closing branch gauge tap.