FloAire Indirect Fired Heater - Manual (Page 17)

17
Flame Safety
Flame Safety Control
The second system to understand is the Flame Safety Control. The FSC is
there only to monitor the flame, NOT to control temperature. The FSC uses a
sensor mounted on the burner pilot assembly to sense for pilot establishment.
The FSC controls the opening of the redundant solenoid gas valves and the
operation of the spark igniter to initiate a pilot flame upon start up. When there
is a call for heat (determined by the Maxitrol system), the LED on the FSC is
energized indicating that the unit has power. Then, there is a Pilot Trial For
Ignition (PTFI). During PTFI, the FSC opens the pilot gas valves and allows gas
to pass through the pilot line. At the same moment, the spark igniter is started,
causing the electrode on the burner to ignite the gas. This results in a pilot flame. When the sensor
detects the flame it powers the main gas valve and the system begins to modulate the flame. This is the
normal operating mode. The FSC continues to monitor the flame for presence.
Operation Summary
With the blower already running and the airflow switch proven;
The outside air temperature falls below the setting of remote temperature selector
The Maxitrol amplifier sends a 24V signal out through the high temperature limit (automatic
switch located in furnace and set at 150°F), the bl ocked vent safety switch, and through the
centrifugal switch of the power vent
•
The FSC in energized by this 24V signal from the Maxitrol amplifier and the following occurs;
FSC indicates that it has power by turning on the LED
Begins Pilot Trial For Ignition
The pilot gas solenoid valve is opened, the electrode begins sparking, and the sensor
watches for flame initiation
When flame is established, the main valve opens and the unit begins modulating
The FSC monitors the flame while the Maxitrol system adjusts to the selected temperature
•
The Maxitrol system checks the discharge air temperature (or the room temperature for the Maxitrol
20/30) and regulates the gas going to the burner to satisfy the temperature setting. The Maxitrol
system will modulate the main burner gas from 100% down to 40% as needed. If the burner
remains on low fire for a short amount of time, the burner will be shut off and restarted as
necessary.