Pentair MiniMax NT LN Safety Controls, Vacuum AIR Pressure FAN Switch, Water Pressure Switch

Section IV. Operation 22

SAFETY CONTROLS

VACUUM AIR PRESSURE (FAN) SWITCH

The air pressure switch, (see Figure 20), is a safety device used to insure that the combustion air blower (fan) is operating and has been designed to monitor the vacuum (negative) pressure within the blower housing. The air pressures switch is factory set and is connected upstream of the ignition module. The ignition module does not operate unless the air pressure switch and all safety switches are closed.

WATER PRESSURE SWITCH

The water pressure switch, (see Figure 21), closes when there is a sufficient flow of water to the heat exchanger to safely operate the heater. The switch has been preset by the Factory at 1½ PSI for operation. NOTE: See, Below Pool Level Installation instructions on page 8. The switch may remain closed with no water flow if there is more than a 3 ft. elevation difference between the heater (heat exchanger) and the pool water line—if this is the case, the water pressure switch must be reset by a qualified service technician to maintain open switch contacts with no water flow.

NOTE

If the pool is more than one floor above or one floor below the heater, the water pressure switch may have to be replaced with a flow switch.

THERMAL FUSE

This is a single-use switch, mounted on combustion chamber jacket divider (inner front panel). The fuse, (see Figure 22), is activated by excessive temperature due to abnormal operating conditions. Upon detection of excessive heat within the inner front panel, the fuse will open the safety circuit causing shutdown of the heater.

LOW GAS PRESSURE SWITCH

The MiniMax NT LN model heater uses a low gas supply pressure switch, (see Figure 23), ahead of the gas valve, to prevent operation of the heater when the gas supply pressure is below the minimum required for proper operation of the burners. The switch is factory set. In the event that the switch does not close and prevents the firing of the heater, the cause of the low gas supply pressure must be corrected. Typical causes are undersized supply piping, undersized gas meter or low gas regulator setting (gas supply regulator and gas meter problems are typically corrected by your local gas company).

Figure 20.

AIR PRESSURE SWITCH

Air Pressure Switch

Figure 21.

Adjustment Knob

Typical Water Pressure Switch

Figure 22.

Thermal Fuse

Figure 23.

Low Gas Pressure Switch

P/N 472089 Rev. E 4-19-05