L.B. White AD250 User Manual

Page 20

SPARK IGNITION OPERATION SEQUENCE:

— A call for heat occurs from the building’s environment

control.

— 1-15 VDC is sent from the SmartBox

™

variable rate heat

controller to the variable rate solenoid on gas control
valve.

— Line voltage is sent to transformer and to ignition control
— 24 V.A.C. is sent from transformer to the ignition control.
— A call for heat occurs
— Red light on ignition control is illuminated
— Ignition control module performs an internal safe start

check
-- Internal components are tested
-- Amperage is sent to flame sensor from ignition

control to start flame proving process.

-- Ignition control terminal PS1 sends 24 volts to air

proving switch.

— Ignition control module begins safety lockout timing
— Ignition control module sends 115 volts from terminal

IND to the fan motor.
-- fan motor starts
-- Air proving switch closes and 24 volts is returned

to ignition control terminal PS2.

— Ignition control powers the igniter and igniter sparks.
— Ignition control sends 24 volts from terminal MV to gas

control through high limit switch.

— Ignition occurs

-- Igniter continues to spark until flame proving

occurs.

-- Igniter spark is discontinued
-- Gas valve stays open

— Room warms to desired temperature

-- Room sensor is satisfied
-- Heater shuts down

— Process begins again on call for heat

MULTIPLE IGNITION TRIAL SEQUENCE

— First trial for ignition takes approximately 10 seconds
— Two more trials for ignition willoccur

-- Second and third trial follow immediately if first

trial fails

— M o d u l e s t a r t s a 15 m i n u te wa i t p e r i o d to a l l ow

ignition interruption to pass

— Ignition control repeats 3 ignition attempts after 15

minute wait period

— If ignition control module does not prove flame after third

trial, the module goes into safety lockout (3 flash pattern)
-- Igniter shuts down
-- Fan motor svtops
-- Gas valve closes

— Ignition control must be reset

-- Unplug the heater and plug it back in

-- OR --

-- Turn building controller off and then back on to call

for heat