The reliability of electrical equipment and automation systems also depends on their surroundings. Excessive humidity, condensation and high temperatures can cause faults, leading to repair costs and unexpected downtime. A hygrostat monitors humidity and switches suitable equipment on when needed. Combined with temperature control, a single controller can perform several tasks.
The ELKO EP RHT-1 combines the functions of a hygrostat and a thermostat. It can control a fan, heater or dehumidifier according to the temperature and relative humidity at its installation location.
Why do humidity and temperature matter?
Components operating inside an electrical enclosure generate heat. If that heat cannot escape adequately, the temperature may rise above a suitable level for the equipment. In humid environments, another problem arises: condensation can form on cool surfaces.
Condensation occurs when a surface temperature falls to or below the dew point of the surrounding air. The absence of visible water droplets therefore does not mean that humidity can be ignored. Monitoring conditions helps identify and respond to changes before they disrupt equipment operation.
What is the difference between a hygrostat and a thermostat?
A thermostat controls connected equipment according to temperature. A hygrostat responds to relative humidity. A hygrothermostat allows both parameters to be considered.
With the RHT-1, you can select the combination of temperature and humidity conditions that closes the relay contact. For example, switching can depend on one threshold being exceeded or on both conditions being met simultaneously. This offers more options than temperature-only control.
What can the RHT-1 control?
The manufacturer identifies several applications:
Fan control to remove excess heat.
Heating control, for example to improve conditions inside an electrical enclosure.
Dehumidifier or cooling equipment control according to the selected conditions.
Alarm activation when temperature or humidity reaches a specified threshold.
Remote notifications can be arranged using a separate notification device. The RHT-1 itself is not an internet-connected remote monitoring device.
Is the RHT-1 hygrothermostat only suitable for enclosure heaters?
The RHT-1 is not limited to switching an electrical enclosure heater on and off. The same relay can control different loads, provided their electrical characteristics and required control logic are compatible with the controller.
However, the manufacturer designed the RHT-1 primarily to monitor conditions inside electrical enclosures. Its temperature and humidity sensor is built into the device, so it measures conditions where the hygrothermostat is installed. For example, a device mounted inside a control cabinet does not automatically measure humidity in an adjoining room.
Key features
Temperature setting range: 0 to +60 °C.
Relative humidity setting range: 50–90%.
Eight selectable switching conditions, plus permanently ON and OFF modes.
Built-in sensor and sensor fault detection.
Fixed hysteresis: 2.5 °C for temperature and 4% for humidity.
One-module-wide housing for DIN rail mounting.
Supply voltage: 24–240 V AC/DC.
One normally open relay contact, rated at 16 A for AC1 loads.
Hysteresis creates a difference between the switching-on and switching-off thresholds, preventing small fluctuations from causing repeated switching. The connected load’s type and starting current must also be considered; a contactor can be used where necessary.
Prevention starts with suitable control
Humidity and temperature control helps create more suitable operating conditions for equipment. It is important to choose the right control method, a suitable fan, heater or dehumidifier, and appropriate threshold settings.