POWER-UP / STANDBY
35-66 with Full-Time Power (R Models only): Upon applying power (24 volts) to the R terminal, the control will reset, perform a self-check routine, flash the diagnostic LED for a second and enter the thermostat scan state.
CALL FOR HEAT
35-65 & 35-66 without Full-Time Power (R Terminal): When a call for heat is received from the thermostat supplying 24 volts to the W terminal, the control will perform a self-check routine, flash the diagnostic LED for a second and begin the safety timing sequence. After an optional 'pre-purge' period, the hot surface ignitor is energized for a heat-up period, followed by the gas valve for the 'trial for ignition' (TFI) period.
Call for Heat - 35-66 Models: In addition to the self-check routine described above, when a call for heat is received from the thermostat supplying 24 volts to the W terminal, the control will check the pressure switch for normally open contacts. The combustion blower is then energized and, once the pressure switch contacts close, an optional 'pre-purge' period begins. After pre-purge, the hot surface ignitor is energized for a heat-up period, followed by the gas valve for the 'trial for ignition' (TFI) period.
Ignition - 35-65 Models: When the flame is detected during the TFI period, the ignitor is de-activated and the gas valve remain energized. The thermostat and main burner flame are constantly monitored to assure that the system operates properly. When the thermostat is satisfied and the demand for heat ends, the gas valve is immediately de-energized.
Ignition - 35-66 Models: When the flame is detected during the TFI period, the ignitor is de-activated and the gas valve and combustion blower remains on. The thermostat, pressure switch and main burner flame are constantly monitored to assure that the system operates properly. When the thermostat is satisfied and the demand for heat ends, the gas valve is immediately de-energized, the control senses the loss of flame signal and initiates an optional 'post-purge' period before de-energizing the combustion blower.
FAILURE TO LIGHT - LOCKOUT
Single Try Models: Should the main burner fail to light or the flame is not detected during the TFI period, the control will lockout. The gas valve will be turned off immediately. For 35-66 models, the combustion blower will be turned off following an optional 'post-purge' period. With the 1 hour reset option, if the thermostat is still calling for heat, the control will automatically reset and attempt a new TFI sequence after one hour.
FAILURE TO LIGHT - LOCKOUT (continued):
Multi-try Models:
Should the main burner fail to light or the flame is not detected during the first TFI period, the gas valve is de-energized and the control performs an optional 'inter-purge' delay before attempting another TFI period. The control will attempt 2 additional TFIs periods before locking out. In lockout, the gas valve will be turned off immediately. For 35-66 models, the combustion blower will be turned off following an optional 'post-purge' period. With the 1 hour reset option, if the thermostat is still calling for heat, the control will automatically reset and attempt a new TFI sequence after one hour.
Lockout Recovery:
Recovery from lockout requires a manual reset by either resetting the thermostat or by removing the 24 volts for a period of 5 seconds.
Loss of Flame - Re-igntion:
If the established flame signal is lost while the burner is operating, the control will respond within 0.8 seconds. The gas valve is de- energized immediately and a new TFI sequence begins. If the burner does not relight, the control will lockout as previously described in the 'Failure to Light - Lockout' section. Multi-try models will make 2 more attempts to light the burner. If flame is re-established, normal operation resumes.
COMBUSTION AIR FLOW PROBLEMS 35-66 Models only:
1. Combustion airflow is continually monitored during the ignition sequence by the pressure switch (PSW terminal). If the pressure switch contacts remain closed for 30 seconds at the start of the ignition sequence without an output signal to the combustion blower, an airflow fault is signaled and the control will remain in this fault mode with the combustion blower off. If the pressure switch contacts later open while there is still a call for heat, the control begins the pre-purge period followed by a normal TFI sequence.
2. If the pressure switch contacts remain open for more than 30 seconds after the combustion blower output (F1 and F2 terminals) is energized, an airflow fault is signaled and the control will remain in this fault mode with the combustion blower on. If proper airflow is later detected from the pressure switch input (PSW terminal), the control begins the pre-purge period followed by a normal TFI sequence.
3. If the airflow signal is lost while the burner is firing, the control will immediately de-energize the gas valve and an airflow fault is signaled. The combustion blower will remain on for the post-purge period and the control continues to monitor the PSW input waiting for airflow to return. If proper airflow is detected during the post-purge period, a normal TFI sequence begins preceded by any pre-purge period. If not, the control will enter a lockout condition with the combustion blower off.
Flame Fault (Full Time Power Models Only): During normal sequence if an erroneous flame signal occurs, due to the gas valve failing to close completely, the controller will energize the combustion blower. Should the gas valve later close completely and the flame signal be removed, the combustion blower will power off following an optional post-purge period.
MOUNTING AND WIRIN
The 35-65 and 35-66 models are not position sensitive and can be mounted vertically or horizontally. The control may be mounted on any surface and fastened with #6 sheet metal screws. Secure the control in an area that will experience a minimum of vibration and remain below the maximum ambient temperature of 80C (175F)
