Think of accurate speed control as the performance governor on a portable evaporative cooler. The pads in the system are wet. Subsequently, vapour enthalpy draws fluid from an onboard reservoir. Meanwhile, a fan is using its angularly fixed blades to cut the air and insert that evaporative substance. In effect, the whole process is at the mercy of several thermodynamic forces. Fan speed control injects the appliance with appliance-regulating power.

Constant-Speed Drawbacks

If the pads are constantly wet, the internal pump is rotating at a steady rate, and there are no other control elements in action, a portable evaporative cooler is an undisciplined site asset. The temperature in the area is spiking then dropping low, but the cooling power might as well be charted on a graph as a flat line. Doors open, machines actuate, the thermal envelope swells, and that flat line isn’t changing. Would an HVAC system utilize this blind control mechanism? It seems unlikely. On the contrary, heating and cooling systems include feedback circuits, a function that’s typically satisfied when a thermostat controls the cooling and heating assemblies in that closed system.

Accurate Speed Control Alternatives

A basic speed control circuit alters the power supplied to the fan. A change in voltage, current, or frequency regulation, alters the rotational velocity of the fan blades. Two options are available when this feedback circuitry is installed. First of all, electronic circuits send a portion of the circuit power back to the controller as a negative feedback signal. If the ambient temperature around the appliance rises, then the negatively oriented signal tells the speed control module things are getting hot. An electronic gate opens in response to the signal, and now the fan speed increases. Alternatively, people are also feedback mechanisms. Down on the factory floor, personnel are sweating. A foreman notices a productivity drop because of the sweltering heat, so he turns the speed control knob up until the fan is spinning at its maximum velocity.

Manually operated variable speed controllers are mounted on many portable evaporative coolers. As the heat spreads, the controls are adjusted until the appliance is discharging a strong, cooling breeze. Large cross-sectional area pads and fully-filled water reservoirs work in concert with powerful pumps to supply the required sponge-saturation effect. Finally, evaporative units also employ multi-speed fans, which use two or three-stage motors. Paired with a digital thermostat and a timer, or a combination thereof, the equipment gains an essential measure of semi-automated versatility. That feature works well in livestock or greenhouse settings, places that rely on accurate speed control.