Thermostats & Hygrostats

Depending on the surrounding environment and the sensitivity of the components they protect, many enclosures require either some type of cooling device to dissipate excessive heat or heaters to prevent the formation of condensate or frost. Some enclosures require both.

But heating and cooling devices typically don't need to run continuously. They need to be controlled, both to prevent overheating or overcooling and to control energy costs.

• Thermostats sense the temperature of the air inside the enclosure and compare it to a setpoint, which is either the minimum or maximum temperature that the enclosure should maintain. The setpoint may be a fixed, preset temperature characteristic of a tamperproof thermostat or the setpoint may be set by the user within the range of an adjustable thermostat.
  
  Thermostats are either Normally Closed (N.C.) or Normally Open (N.O.) with contacts being closed or open when the surrounding temperature is less than the thermostat's setpoint.
  • N.C. thermostats are identifiable by either a red module on tamperproof thermostats or a red adjustment dial on adjustable thermostats.
  • N.O. thermostats are identifiable by either a blue module on tamperproof thermostats or a blue adjustment dial on adjustable thermostats.
• Hygrostats (also known as humidistats) sense the relative humidity of the air inside the enclosure. If the relative humidity rises above the setpoint, the contacts close to start a heater. Since warm air can hold more water vapor than cold air, the temperature increase caused by the heater causes the relative humidity to decrease, reducing the exposure to moisture and corrosion issues.
• Hygrotherms sense both temperature and relative humidity and start a heater if the temperature falls below or the humidity exceeds the setpoint.

Different types of thermostats, hygrostats, and hygrotherms have various switching differences and tolerances. Users should take these characteristics into account when selecting a control device for their application.

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