Heating Systems In Hot Tubs And Spas Use Use Reed Sensors REED RELAYS REED SENSORS REED SWITCHES Introduction The volume of hot tubs or spas are being used more and more around the world for medicinal reasons and for shear joy. An essential part of a hot tub is its heating system. There are very high wattage heaters that are designed into hot tubs for quick warm up. If for some reason the water is not flowing and the heaters are activated, the heat would begin boiling and overheating of essential flow components resulting in some serious damage to the hot tub. Hot tub designers have found a reliable solution using MEDER’s reed sensors. 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 mini paddle wheel, and the Reed Sensor is mounted strategically such that the magnetic field of magnet will be sensed with each rotation of the paddle wheel. Figure 2. No water is flowing so the spring magnet is retracted away from the reed switch keeping the heating unit OFF. • The reed switch used in the Reed Sensors is hermetically sealed and is therefore not sensitive to wet, watery environment • The magnet is not affected by its environment • Tens of millions of reliable operations • Surface mounting and through hole mounting • Cylindrical hole and screw fastening mounting • Contacts dynamically tested Applications • Ideal for sensing spring movement in water flow systems within a hot tub or spa. • Ideal for applications sensing any type of spring movement in a host of different configurations Figure 3. Water flow causes the spring magnet to move into proximity with reed switch causing the contacts to close which switches the heating unit ON. Reed Sensors are the Choice for Measuring the Volume of Water Flowing Through a Filters Hot tubs and spas are used around the world with many mounted in back yards, on decks, and in special spa rooms in the house. The hot tubs usually have heated water at approximately 38˚C (100˚F). To maintain this temperature, thermocouples sense when the temperature drops to a certain level, which will then turn on strong wattage heaters. Just prior to this, the water flow system will be energized. Turning on the heaters with the water not flowing will create a potentially dangerous situation because if the water is not flowing the localized water will be super heated and begin boiling. This can then leave areas with no water. With the heaters continuing to pump out their high wattage, the plastic vessels housing the water flow system could begin to melt or potentially burn with catastrophic results. Spa designers have chosen MEDER’s reed sensors as a very reliable solution. 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 Heating Systems In Hot Tubs And Spas Use Use Reed Sensors REED RELAYS REED SENSORS REED SWITCHES Specifications Defining the MK06 & MK15 Series Operate specs Min Max Units Must close distance 5 25 mm Must open distance 5 25 mm Hysteresis Load Characteristics Switching voltage Switching current Carry current Contact rating Static Contact resistance Dynamic contact resistance Breakdown voltage Operate time Release time Operate Temp MK06 Storage Temp MK06 Operate Temp MK15 Storage Temp Temp MK15 Typical 50% Min Max Units 200 0.5 1.5 10 150 200 320 -20 -20 -20 -20 0.5 0.1 85 85 130 130 V Amps Amps Watts mΩ mΩ V msec msec °C °C °C °C Designers have developed a spring that will deflect when there is water flow in a spa. The spring has a magnet attached to it. When the spring moves, the magnet will move along with it . The reed sensor senses this movement and sends a signal to the electronics alerting it that water is flowing. Armed with this information, the electronics will signal an okay to turn on the heaters when the heat sensors call for more heat. In this way reliable operation is achieved and happy customers are maintained. Because MEDER’s sensors use hermetically sealed reed switches that are further packaged in strong high strength plastic, they can be subject to watery environments without any loss of reliability. 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. MEDER’s sensors are packaged for surface mounting as well as through hole mounting. Also, MEDER has cylinder packages as well as screw fastening packages having lead wires for remote attachment to the electronics. Consider some of the below options in surface mount, through hole, cylindrical and rectangular versions for water flow sensors or similar applications. Surface Mount Series Series MK15 MK16 MK17 MK22 MK23MK23-35 MK23MK23-66 MK23MK23-87 Figure 3. MK15 Tape & Reel MK23MK23-90 Dimensions mm W 2.5 H 2.5 L 19.50 W 2.3 H 2.3 L 11.50 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 2.54 H 3.05 L 24.9 Illustration inches 0.098 0.098 0.768 0.091 0.091 0.453 0.083 0.083 0.378 1.060 0.091 0.614 0.087 0.077 0.620 0.087 1.060 0.772 0.079 0.083 0.614 0.100 0.120 0.980 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 Heating Systems In Hot Tubs And Spas Use Use Reed Sensors 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 5.25 L 25.5 Illustration inches 0.207 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 the factory for more options not listed above. ** 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