Hayward Universal H-Series Low NOx Service/Installation: H150FDN H200FDN H25 - Page 47
High Limit Switches, To Replace A High Limit Switch
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47 To remove the blower vacuum switch: 1. Turn pump, gas supply, and heater power "OFF". 2. Remove the front access panel. It is secured with (4) screws 3. Remove the wires from the pressure switch. 4. Pull the tubing from the hose barb on the switch. 5. Remove the (2) screws that secure the pressure switch to the control panel. 6. Replace the switch. Reverse steps 1 - 6 to complete the procedure. High limit switches: The high limit is an automatically resetting safety device wired in series with the thermostat and gas valve. See Figure 36. The heater is equipped with two automatic high limits, located on the water header, below the outlet water connection. The limits have the same temperature settings and are interchangeable. If the water temperature exceeds the limit set point, the gas valve will be closed, shutting off gas supply to the burners. Erratic high limit operation is often an indication of a problem with water flow. Reduced flow may be caused by: 1. Clogged filter or strainer. 2. Excessive flow through the external bypass if one is used. 3. Lime scale accumulation in the heat exchanger. To replace a high limit switch: 1. Turn pump, gas supply, and heater power "OFF". 2. Drain the heat exchanger of all water. 3. Unplug the high limit wires from the wiring harness. 4. Unscrew the high limit switch from the header. 5. Replace the high limit switch. Use new sealant on the high limit switch threads before reinstalling. Reassembly is a reverse of steps 1 - 4. Figure 46: High Limit Switch USE ONLY HAYWARD GENUINE REPLACEMENT PARTS Pomona, CA Clemmons, NC Nashville, TN Tel: 908-351-5400 www.haywardpool.com