Aiko CTH3-150 Manuale Utente

56 of 71

The control inside the heater's control compartment 
is equipped with a tri-color LED. The LED offers 
comprehensive diagnostic capability. The LED 
status will be referenced throughout this section.

1. When the control is powered and there is no call 

for heat from external heat demand device, the 
LED on the control flashes slow green; LED is 
ON for the same period it is OFF.

2. On a call for heat from the heat demand device, 

the heater will go to PRE-PURGE. The LED 
indicates one green flash. The blower speed will 
vary as the pressure switch setpoints are 
verified. When the PRE-PURGE is successfully 
completed, the heater will go into the 
PRE-IGNITION state and power the hot surface 
igniter (H.S.I.). 

3. After the igniter warms up, the heater will go to 

the IGNITION state. Power is supplied to the 
gas valve operator, gas flows, ignites and the 
flame is proven. The LED shows two green 
flashes on the LED. If a flame is not sensed, the 
heater will RETRY, 

See Item 6 below for further 

details.

4. When the IGNITION state is completed, the 

heater will go to WARM UP state. The unit will 
fire at maximum input for 15 seconds. When the 
WARM UP state is completed the device will go 
into RUN state. The control board will monitor 
the heat demand device and modulate the 
heater input to meet the demand. The LED still 
shows two green flashes.

5. When the call for heat has been satisfied, the 

heater closes the gas valve. The blower 

continues to run for a 45 second post-purge 
period. After the post-purge, the heater turns 
OFF and the LED on the control board flashes 
slow green.

6. If flame is lost at any time during heater 

operation, the heater will RETRY for ignition. 
Upon RETRY the LED shows a fast yellow flash 
(LED rapidly flashes). The heater will RETRY for 
ignition three times. After four ignition attempts, 
the heater will lockout for one hour or until reset. 
To reset the heater, remove power for 10 
seconds, then re-apply power. Turn heater ON 
with call for heat from the heat demand device.

Set external heat demand device to lowest setting.

Turn OFF electric power to heater.

Turn OFF manual gas valve in the heater supply line.

Turn gas valve and electric power OFF and wait five 
minutes for unburned gases to vent from heater.

Turn ON main gas valve.

Turn ON electric power.

Set heat demand device to desired temperature. 
Burner should light automatically.

To ensure your safety and years of trouble-free 
operation of the heating system, service and annual 
inspections must be done by a contractor qualified in 
the installation and service of gas-fired heating 
equipment.

Turn off gas and electric supplies before performing