Hayward Universal H-Series Low NOx Service/Installation: H150FDN H200FDN H25 - Page 48

Thermistor, Water Pressure Switch

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48 Thermistor: Figure 47: Thermistor The thermistor monitors the return water temperature. See Figure 47. To replace the thermistor: 1. Turn pump, gas supply, and heater power "OFF". 2. Drain the heat exchanger of all water. 3. Remove the front access panel. It is secured with (4) screws 4. Remove the control box cover. It is secured with (2) screws. 5. Unplug the thermistor connector from the ignition control board. 6. From outside the heater, pull the thermistor leads out of the control box and through the hole in the heater chassis. 7. Unscrew the thermistor from the inlet side of the header. 8. Replace the thermistor. Use new sealant on the thermistor threads before re-installing. Reverse steps 1 - 7 to complete the procedure. WATER PRESSURE SWITCH: The water pressure switch (Figure 48, see Figure 45 for its location) is factory pre-set for deck-level installations. When the heater is located below Figure 48: the level of the spa or pool, the water pressure switch may require an adjust- Water pressure switch: ment to compensate for the no-flow static head. The following procedure is recommended when the switch needs adjustment and/or replacement: 1. Be sure the filter is clean before making any adjustment. 2. With the pump "ON" in either "POOL" or "SPA" mode (the heater is "ON"), turn the adjustment dial on the pressure switch clockwise until a "click" is heard from the gas valve. 3. Turn the adjustment dial counterclockwise ¼ turn. 4. Turn the pump "OFF" and "ON" several times. The heater should shut off immediately when the pump is shut off. If the heater fails to shut down with the pump, repeat the steps above until the switch is adjusted properly. ATTENTION: Do not operate the pool heater without the function of a properly adjusted pressure switch or flow switch. To replace the pressure switch: 1. Turn pump, gas supply, and heater power "OFF". 2. Unplug the high limit terminals from the main wire harness. 3. Remove the (4) screws securing metal trim panel around the header. 4. Remove the wires from the pressure switch. 5. Using two ½" open-end wrenches disconnect the pressure switch from the pressure switch tubing. 6. Replace the pressure switch. Use new sealant on the pressure switch threads before re-installing. 7. Reverse steps 1 - 5 to complete the procedure. USE ONLY HAYWARD GENUINE REPLACEMENT PARTS Pomona, CA Clemmons, NC Nashville, TN Tel: 908-351-5400 www.haywardpool.com

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Pomona, CA Clemmons, NC Nashville, TN
Tel: 908-351-5400
www.haywardpool.com
USE ONLY HAYWARD GENUINE REPLACEMENT PARTS
48
Figure 47: Thermistor
THERMISTOR:
The thermistor monitors the return water temperature. See Figure 47. To replace the thermistor:
1. Turn pump, gas supply, and heater power “OFF”.
2. Drain the heat exchanger of all water.
3. Remove the front access panel. It is secured with (4) screws
4. Remove the control box cover. It is secured with (2) screws.
5. Unplug the thermistor connector from the ignition control board.
6. From outside the heater, pull the thermistor leads out of the control box and through the hole in the
heater chassis.
7. Unscrew the thermistor from the inlet side of the header.
8. Replace the thermistor. Use new sealant on the thermistor threads before re-installing. Reverse steps
1 – 7 to complete the procedure.
WATER PRESSURE SWITCH:
The water pressure switch
(Figure 48, see Figure 45 for its location) is
factory pre-set for deck-level installations. When the heater is located below
the level of the spa or pool, the water pressure switch may require an adjust-
ment to compensate for the no-flow static head. The following procedure is
recommended when the switch needs adjustment and/or replacement:
1. Be sure the filter is clean before making any adjustment.
2. With the pump “ON” in either “POOL” or “SPA” mode (the heater is
“ON”), turn the adjustment dial on the pressure switch clockwise until a
“click” is heard from the gas valve.
3. Turn the adjustment dial counterclockwise ¼ turn.
4. Turn the pump “OFF” and “ON” several times. The heater should shut
off immediately when the pump is shut off. If the heater fails to shut
down with the pump, repeat the steps above until the switch is adjusted
properly.
ATTENTION:
Do not operate the pool heater without the function of a properly adjusted pressure
switch or flow switch.
To replace the pressure switch:
1. Turn pump, gas supply, and heater power “OFF”.
2. Unplug the high limit terminals from the main wire harness.
3. Remove the (4) screws securing metal trim panel around the header.
4. Remove the wires from the pressure switch.
5. Using two ½” open-end wrenches disconnect the pressure switch from the pressure switch tubing.
6. Replace the pressure switch. Use new sealant on the pressure switch threads before re-installing.
7. Reverse steps 1 – 5 to complete the procedure.
Figure 48:
Water pressure switch: