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Manafacture: Aprilaire File size: 2.35 mb File name: Language of manual:

................................................................................................................................................................................ AIRFLOW PROVING SWITCH INSTALLATION INSTRUCTIONS Description: FIGURE 20 The airflow proving switch is a safety device that will prevent the humidifier from producing steam when there is no airflow present in the HVAC system. The switch is a pressure differential measuring device that determines if there is airflow present based on the pressure differential between the HVAC system and atmosphere. The switch contains a diaphragm, calibration spring, and a snap acting SPDT switch. See Figure 20 for details. Operation: When the HVAC equipment fan is off, the airflow proving switch is open. In the event of a demand “call” from the humidistat in this state, the airflow proving switch would prevent the humidifier from starting or producing steam. When the airflow proving switch senses that the HVAC equipment fan is on, the switch closes. This position will allow the humidifier to come on and produce steam. Installation: The airflow proving switch is mounted on any surface free from vibration. The airflow proving switch must be installed with the diaphragm in a vertical plane. (See Figure 20 for acceptable and unacceptable mounting configurations.) Avoid mounting the switch with the inlet line connections facing up. The air sampling probe (included) must be located a minimum of 1.5 duct diameters downstream from the discharge of the HVAC equipment blower. It is connected to the airflow proving switch by a 1/4” field supplied plastic tubing. The hose is connected to inlet H on the switch housing, while inlet L remains open to the atmosphere. (See Figure 20) Using the ‘Normally Open’ and ‘Common’ terminals inside the terminal enclosure, wire the airflow proving switch to the field wiring terminal block in the humidifier according to the wiring diagram on page 21 depending on the humidifier model number. See Figures 16-19 on page 21. The airflow proving switch is field adjustable from .05” w.c. to 12” w.c.. To adjust the set point, turn the adjusting screw counter clockwise (CCW), until motion has stopped. Next, turn the adjusting screw 4 complete turns in a clockwise direction to engage the spring. From this point, the next 10 turns will be used for calibration. The optimum setting is one that will only close the switch when the fan is in operation. Each full turn of the adjustment screw represents approximately 1.2” w.c. To properly calibrate an airflow proving switch, a digital manometer or other pressure measuring device should be used to confirm the actual set point. Diaphragm Mounting Bracket Terminal Enclosure Inlet L: Low Inlet H: High Do not mount in this manner. Diaphragm must be mounted in a vertical plane SUPPLY WATER AND DRAIN PIPING The humidifier is designed to operate with hot or cold, hard or soft water. Be sure to set slide switches on the internal controller board to guidelines on page 11. Supply water piping may be of any code-approved material (copper, steel, or plastic). The fill valve connection size is a .” (DN8) compression fitting. In cases where water hammer may be a possibility, consider installing a shock arrestor. Water pressure must be between 25 psi and 80 psi (175 kPa and 550 kPa). Drain piping may be of any code-approved material (copper, steel, or plastic rated for 140°F [60°C] minimum). If drainage by gravity is not possible, use a reservoir pump rated for 140°F (60°C) water. Notes: • Dashed lines indicate provided by installer. • The water supply inlet is more than 1” (25 mm) above the skim/overflow port, eliminating the possibility of backflow or siphoning from the chamber. No additional backflow prevention is required; however, governing codes prevail. Shock arrester recommended to reduce water hammer .” (DN8) compression fitting on fill valve connection to water supply line; water pressure must be between 25 psi and 80 psi (175 kPa and 550 kPa); water conductivity minimum 100 .S/cm2; fill valve has an integral strainer Water supply line Spill funnel; plumb to floor drain 1” (25 mm) air gap .” (DN20) copper chamber drain and overflow piping, rated for 140°F (60°C). If piping run is over 10’ (3 m) increase pipe to 1.” (DN32). Open drain required. Locate air gap only in spaces with adequate temperature and air movement to absorb flash steam; otherwise, condensing on nearby surfaces may occur. Refer to governing codes for drain pipe size and maximum discharge water temperature. Install plumb Steam hose (maximum run 10’ [3 m]) OM-4017 1” (25 mm) flexible drain hose and clamps FIGURE 21 – Field Piping Overview Showing Hose Drain Connection The final connection size is 1” (DN25) hose or .” (DN20) copper for the chamber drain. Do not reduce this connection size. (See Figures 21 and 22 for proper drain piping configurations.) A 12” (305 mm) piece of 1” (DN25) hose is provided to function as the flexible connection...

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