Air Conditioners and Dehumidifiers Dehumidifiers Use Reed Sensors to Sense the Upper Limit of Their Reservoirs REED RELAYS REED SENSORS REED SWITCHES Introduction In the summer months, warm and humid air invades the area. This is the case in most regions of the world. Depending how close one is to the equator this condition may exist throughout the year. During this time, many businesses and homes are equipped with air conditioners and Dehumidifiers to cool the air and reduce the humidity. A typical unit can accumulate up to 15 gallons (60 liters) of water in a single day. With this much water being produced, care must be taken with the reservoirs to prevent water overflow. Reed sensors provide a reliable way to detect maximum levels to either alert the user or turn on a water pump. Figure 1. MK17-x-3 Sensor physical layout Features • Magnet and Reed Sensor are isolated and have no physical contact by typically having the magnet mounted to a float and the Reed Sensor is mounted on the body of the casing close to the high point of the water and positioned to accurately pick up the magnetic field from the magnet in the float. • The reed switch used in the Reed Sensor is hermetically sealed and is therefore not sensitive to rough, wet, moist environments Figure 2. Pump is off until magnetic float moves up the reed sensor once the water reaches the highest level in the reservoir. • The magnet is not affected by its environment • Tens of millions of reliable operations • Surface mount and through hole packages available • Cylindrical hole and screw fastening mounting • Contacts dynamically tested Applications • Ideal for sensing the water level in air conditioners and Dehumidifiers • Ideal for applications sensing any kind of liquid level in a host of different configurations Figure 3. When water reaches highest level, magnetic float moves up the reed sensor switching the pump on. The pump will remain on until the internal circuitry senses the current change at the lowest point in the tank. Air Conditioners and Dehumidifiers Dehumidifiers Use Reed Sensors to detect Reservoir Full Conditions Many of us must have our air conditioners running full force in the warm humid months. The air conditioners do a great job of cooling and reducing the air temperature. They also remove some of the humidity, but most of the time not enough to eliminate mildew and mold that loves moist warm environments. This mold and mildew can cause allergy outbreaks and affect people with asthma. So, many times air conditioners and Dehumidifiers will be working together in unison. Both systems condense a serious amount of water vapor from the air creating large volumes of water. Storage containers or reservoirs must be monitored in some fashion for potential water overflow. MEDER’s reed sensors have made an excellent choice in carrying out this monitoring. MEDER electronic Application MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: [email protected] MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: [email protected] Page 1 of 3 www.meder.com Air Conditioners and Dehumidifiers Dehumidifiers Use Reed Sensors to Sense the Upper Limit of Their Reservoirs REED RELAYS REED SENSORS REED SWITCHES Specifications Operate specs Min Max Units Must close close distance 5 25 mm Must open distance 5 25 mm Hysteresis Load Characteristics Switching voltage Switching current Carry current Contact rating Static Contact Contact resistance Dynamic contact resistance Breakdown voltage Operate time Release time Operate Temp (MK15) Storage Temp (MK15) Typical 50% Min Max Units 200 0.5 1.5 10 150 200 320 0.5 0.1 -20 130 -35 130 Volts Amps Amps Watts mΩ mΩ Volts msec msec °C °C A magnet is generally mounted in a float that rides up and down with the water level in the storage container or reservoir. As the water level reaches the upper limit, MEDER’s reed sensor, which is conveniently positioned near the top of the reservoir, will sense this high water mark. For manually emptied air conditioners and Dehumidifier models, the reed sensor will directly switch off these models. Some of the models are equipped with a beeping sound and/or a water full light will be turned on, alerting the user its time to empty the water. Once the water is emptied, the air conditioner and/or the Dehumidifier will turn back on. However, in more and more models the reed sensor will switch on a water pump instead, allowing water to be emptied automatically where the water is pumped into a water drain system. Having a pump that only turns on when the reservoir is full is very energy efficient, compared to having the pump running all the time. The reed sensor is an excellent choice because it can operate reliably over a wide temperature range, and represents an economical way to carry out the sensing function. Because MEDER’s sensors use hermetically sealed reed switches that are further packaged in strong high strength plastic, they can be subject to rough treatment and environmental concerns such as spillage water, and moisture without any loss of reliability. MEDER’s sensors are packaged for surface mounting as well as through hole mounting. Also, MEDER has cylinder packages and well as screw fastening packages having lead wires for remote attachment to the electronics. Surface Mount Series Series Series MK15 MK16 MK17 MK22 MK23MK23-35 MK23MK23-66 Figure 4. MK15 Tape & Reel MK23MK23-87 MK23MK23-80 Dimensions mm W 2.5 H 2.5 L 19.50 W 2.3 H 2.3 L 15.60 W 2.1 H 2.1 L 9.61 W 2.7 H 2.3 L 15.60 W 2.2 H 1.95 L 15.75 W 2.2 H 2.7 L 19.60 W 2.0 H 2.1 L 15.60 W 2.0 H 2.1 L 13.0 Illustration inches 0.098 0.098 0.768 0.091 0.091 0.614 0.083 0.083 0.378 0.106 0.091 0.614 0.087 0.077 0.620 0.087 0.106 0.772 0.079 0.083 0.614 0.079 0.083 0.512 MEDER electronic Application MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: [email protected] MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: [email protected] Page 2 of 3 www.meder.com Air Conditioners and Dehumidifiers Dehumidifiers Use Reed Sensors to Sense the Upper Limit of Their Reservoirs REED RELAYS REED SENSORS REED SWITCHES Through Hole Series Series MK06MK06-4 MK06MK06-5 MK06MK06-6 MK06MK06-7 Dimensions mm W 3.3 H 3.3 L 12.06 W 2.8 H 3.2 L 14.30 W 3.3 H 4.2 L 17.24 W 3.3 H 4.2 L 19.78 Illustration inches 0.130 0.130 0.475 0.110 0.126 0.563 0.130 0.165 0.679 0.130 0.165 0.779 Cylindrical Panel Mount Series Series MK03 MK03 Dimensions mm Dia 5.80 L 25.5 Illustration inches 0.244 1.004 MK14 MK14 Dia L 4 25.5 0.157 1.004 MK18 MK18 Dia L 5 17 0.197 0.669 MK20/1 MK20/1 Dia L 2.72 10 0.107 0.394 Rectangular Screw Flange Mount Series Series MK04 MK05 MK05 MK12 MK12 Dimensions mm W 13.9 H 5.9 L 23.0 W 19.6 H 6.1 L 23.2 W H L 14.9 6.9 32.0 Illustration inches 0.547 0.232 0.906 0.772 0.240 0.913 0.587 0.272 1.260 **Consult our factory for your specific design requirements. ** MEDER electronic Application MEDER electronic AG | Germany | tel.: +49(0)7731/8399-0 | Email: [email protected] MEDER electronic Inc. | USA | tel.: +1 508.295.0771 | Email: [email protected] Page 3 of 3 www.meder.com