THE TOTAL SOLUTION FOR GAS IGNITION CONTROL
Fenwal offers a complete range of ignition control products including:
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- Ignition Controls
- Spark and Flame Sense Electrodes
- Spark and Flame Sense Cables
- Wiring harnesses
Designed, developed and manufactured by Fenwal, these components integrate seamlessly providing maximum system performance.
Getting Started - Samples
To ensure proper system design and operation, Fenwal provides sample ignition controls, high-voltage wires and electrodes for trial and evaluation at no charge. To get you started quickly, Fenwal has identified our most popular ignition controls, see Page 8. Whether it is an individual control, complete start-up kit or customized control, Fenwal is ready to provide your gas ignition solution.
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Fenwal Ignition Development Center
Send your equipment to us and we'll design, install and qualify a control to meet your exact application requirements. Fully equipped and staffed with trained technicians, the Fenwal Ignition Development Center has proven extremely beneficial for many customers focused on product quality and reducing time-to-market for their appliances.
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Start up - Heat Mode
120 VAC is supplied to the L1 terminal, either from a thermostat or other control device. When this occurs the control will power up and perform a self-check routine and if selected, begin a pre-purge. Following the pre-purge, the gas valve is energized and sparks commence until flame is detected or the Trial for Ignition (TFI) period expires.
When flame is detected, the spark is shut off and the gas valve and combustion blow- er remain energized. The thermostat, pressure switch and main burner flame are constantly monitored to ensure that the system is functioning properly. When the thermostat is satisfied and the demand for heat ends, the gas valve is de-energized immediately and a post-purge is initiated (optional) and the flame is extinguished. When the post purge is complete, the combustion blower is de-energized.
System Response to Flame Failures
Fenwal controls are configured with several options for managing loss of flame.
Failure during TFI Period
SINGLE TRIAL MODEL
Should the burner fail to light or flame is not detected during the TFI period, the gas valve is de-energized and the control will go into lockout mode.
MULTI TRIAL MODEL
Should the burner fail to light or flame is not detected during the first TFI period, the gas valve is de-energized and the control will attempt two additional ignition trials with inter-purge. If these attempts are unsuccessful, the control will go into lockout mode.
Failure of Established Flame- Two Options
There are two methods for re-starting the burner after loss of established flame. The Re-ignition option is the default configuration for re-establishing flame and does not need to be specified when ordering. If the Recycle option is desired, please specify this when ordering so that a special part number is assigned to the control by Fenwal.
RE-IGNITION
If the established flame signal is lost, the control responds and begins sparking within 0.8 seconds of loss of flame. This is considered the first re-ignition attempt. The spark will be energized for the duration of the TFI period in an attempt to re-light the burner. If flame is re-established, normal operation resumes.
SINGLE TRIAL MODEL
If the burner does not light after the first re-ignition attempt, the control will de-energize the gas valve and go into lockout mode.
MULTI TRIAL MODEL
If the burner does not light after the first re-ignition attempt, the inter- purge sequence is completed between the next two attempts to re-light the burner. If the burner fails to light after the third attempt, the control will de-energize the gas valve and go into lockout mode.
RECYCLE
If the established flame signal is lost, the control responds by shutting off the gas valve within 0.8 seconds.
SINGLE TRIAL MODEL
The control will begin the ignition cycle with the pre-purge cycle, if a pre-purge cycle is programmed into the control. Controls without pre-purge immediately commence sparking for one TFI period. If flame is re-established, normal operation resumes. If the burner fails to light after the first try, the control will de-energize the gas valve and go into lockout mode.
MULTI TRIAL MODEL
The control will begin the ignition cycle with the inter-purge sequence and attempt three tries for ignition including inter-purges. If flame is re-established, normal operation resumes. If the burner fails to light after the third try, the control will de-energize the gas valve and go into lockout mode.
Combustion Air Flow Monitoring
In normal operation, the control monitors the combustion air flow by reading the pressure switch (PSW) input to confirm that the blower is operating in the proper sequence. Initially, the control checks the PSW input to be sure that it is open. Once the blower is energized and the PSW closes the control proceeds to trial for ignition.
If during a call for heat 120 VAC power is present at the PSW input prior to the blower being energized, the control will wait 30 seconds, for the condition to change. Possible reasons for this condition includes a stuck or mis-wired pressure switch, or the blower is spinning down and keeping the switch closed. If the condition does not change, an airflow fault will be declared and the LED will flash the one flash pattern.
If the combustion blower is energized and the PSW does not close within 30 seconds, an airflow fault will be declared and the LED will flash the one- flash pattern. The blower will remain energized until the condition changes.
If the PSW signal is lost while the burner is firing, the control will immediately de-energize the gas valve and the combustion blower will remain on. If the call for heat remains and the PSW signal returns within 30 seconds, the control will restart with the pre-purge period. If the PSW input does not return within 30 seconds, the blower remains on and LED will flash the one-flash code indefinitely. If the PSW closes, the LED stops flashing and the control resumes oper- ation with the pre-purge function.
Lockout Mode (On-Board Safety System)
After single or multiple attempts to light the burner have failed or flame is not estab- lished, the control automatically enters lockout mode. The control will not open the gas valve unless there is intervention by the user or one hour has passed depending on the model chosen. See Lockout Recovery
Lockout Recovery - Two Options
There are two options for recovering from lockout mode. When selecting the control, please specify one of the following methods for lockout recovery.
- Thermostat/ Power Off Reset- requires the user to reset the thermostat below ambient temperature or remove the 120 VAC power supply for 5 seconds. The control will start the ignition sequence and attempt to light the burner again.
- Automatic Reset - After one hour, if the thermostat is still calling for heat, the control will automatically start the ignition sequence and attempt to light the burner again.
Benefits of Full Time Power
- Separate 120 VAC input for ignition control operation and combustion blower operation. Allows high current to feed the blower directly rather than have it pass through the thermostat.
- Sense flame even with zero second pre-purge to provide safe operation. Control will monitor flame presence immediately upon a call for ignition.
- Post purge blower operation to clear the combustion chamber and remove remaining heat when the call for heat has ended.
- If a flame is detected during pre-, inter- or post-purge, the combustion blower will be energized. Should the main valve later close and the flame signal disappear, the combustion blower will be de-energized.
MOUNTING AND WIRING
The 35-71 is 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).
All connections should be made with ULapproved, 105C rated, 18 gauge, stranded, 0.054 in. thick insulated wire. Refer to the appropriate wiring diagram when connecting the 35-71 to other components in the system. High voltage spark cables and control wiring harnesses are detailed on Pages 5 and 6.
