4.Internal and External Pilot Air Supply
On
This can be used to prevent both sets of tilting pistons from extending their rods at the same time. When the front tilting piston rods are extended, 80 PSI (551.6 kPa) air is connected to the bottom piston ports, while the top piston ports are bled to the atmosphere. So, by tapping the external pilot air supply to the rear tilting rods are extended, then there is no pilot pressure available to the rear tilting piston solenoid valve so that its spool cannot move and the rear tilting piston rods cannot extend if a 120 volt signal is sent to its “12” side solenoid valve coil.
The external pilot air supply to the front tilting piston is tapped off the rear tilting piston top port air line so that whenever the rear piston rods are extended, there is no pilot air supplied to the front tilting piston solenoid valve and the front tilting piston rods cannot extend. On the solenoid valve supplied on the dryer, the “12” side valve is externally piloted, while “14” side valve is internally piloted.
A valve can easily be checked for internal or external piloting by removing the two (2) screws which hold the solenoid operator onto the valve. For an internal pilot air to be supplied to the valve spool. For an external pilot, the solid sealing disc must be positioned on top of the internal port.
5.Loading Doors and Heat Reclaimer, Cool Down and Intake Air Damper
These solenoid valves are located in the
The three (3) pistons that control the heat reclaimer damper, cool down damper, and intake air damper are controlled by a single
To open the front loading door, a 120 volt signal is applied to “S1,” the coil of the valve that supplies air to the load door or the heat reclaimer’s bottom port. The valve will open, and 80 PSI (551.6 kPa) of air is supplied to the bottom port of the piston. The piston rod will extend, and the door will open. No voltage is applied to “S2,” the coil of the valve that controls the air supply to the door pistons top port so that this line is bled to the atmosphere.
To close the front loading door or heat reclaimer damper, the voltage signals are reversed, and the loading door will close.
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