USE ONLY GENUINE REPLACEMENT PARTS 37
BLOWER VACUUM SWITCH: The blower vacuum switch is a safety device that prevents the ignition sequence from continuing
unless the blower is developing sufficient airflow for combustion. Figure23: Location of Components shows the location of the
blower vacuum switch in the heater cabinet. When the blower achieves sufficient airflow, the negative pressure created in the
blower housing closes the contacts on the blower vacuum switch, indicating to the ignition control board that it is safe to continue
the ignition sequence. A silicone tube connects the blower vacuum switch with the blower as shown in Figure23: Location of
Components.
To remove the blower vacuum switch:
1. Turn pump, gas supply, and heater power “OFF”.
2. Remove the front access panel.
3. Remove the wires from the vacuum 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 pressure switch and reverse the above procedure to reassemble unit.
HIGH LIMIT SWITCHES: The heater is equipped with two automatic high limits, located on the water header. These high limits are
automatically resetting safety devices wired in series with the thermostat and gas valve. See Figure28: Heat Exchanger Header. 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 an indication of water flow issues. Reduced flow may be caused by a clogged filter or strainer, excessive flow
through the external bypass (if one is used), or 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.
6. Reverse the above procedure to reassemble unit.
VENT PRESSURE SWITCH: The vent pressure switch is a safety device that disables the unit when the flue opening is blocked,
which prevents sufficient combustion gas flow through the unit. Figure23: Location of Components shows the location of the vent
pressure switch in the heater cabinet. When the flue is blocked, pressure is created and opens the contacts on the vent pressure
switch, directing the ignition control board to deactivate the unit. A silicone tube connects the vent pressure switch to the blower as
shown in Figure23: Location of Components.
To remove the vent pressure switch:
1. Turn pump, gas supply, and heater power “OFF”.
2. Remove the front access panel.
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 heater.
6. Replace the pressure switch and reverse the above procedure to reassemble unit.
EXHAUST GAS TEMPERATURE LIMIT: The exhaust gas temperature limit monitors the flue gas temperature above the heat
exchanger and opens when the temperature rises high enough to indicate that the heat exchanger is no longer transferring heat to
the pool water effectively. If the temperature limit opens, effort must be made to assess and rectify the condition that activated the
temperature limit and potentially damaged the heat exchanger. The condition is generally low water flow and/or scaling of the heat
exchanger cupronickel tubes from poor water chemistry. Replace the limit as well as the heat exchanger, if needed, before
operating the unit again.
To replace the exhaust gas temperature limit:
1. Turn pump, gas supply, and heater power “OFF”.
2. Remove the upper end cap on the header side of the unit (see Figure1: Sub-Assemblies).
3. Unplug the two wires from the exhaust gas temperature limit located in the flue collector panel above the middle of the header.
4. Unscrew the (2) screws securing the limit to the panel and remove the limit and gasket.
5. Place the new limit and gasket in place and reverse the above procedure to reassemble unit.
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