Effective: March 2020
2
F-35-703
SEQUENCE OF OPERATION / FLAME
RECOVERY / SAFETY LOCKOUT
Start Up - Heat Mode
When a call for heat is received from the thermostat supplying
120VAC to L1, the control will reset, perform a self-check
routine, flash the diagnostic LED and begin a pre-purge delay.
Following the pre-purge period, the pilot gas valve is energized
and sparking commences for the Trial For Ignition (TFI) period.
When flame is detected during the TFI, the sparking process is
terminated and the main gas valve is energized. The thermostat
and pilot burner flame are constantly monitored to assure proper
system operation. When the thermostat is satisfied and the
demand for heat ends, the pilot and main valves are immediately
de-energized.
Failure to Light - Lockout
SINGLE TRIAL MODEL
Should the pilot burner fail to light, or the pilot flame is not
detected during the TFI period, the pilot gas valve will de-
energize and the control will go into lockout. The LED will
indicate the fault code for ignition lockout.
MULTI TRIAL MODEL
Should the pilot burner fail to light or the pilot flame is not
detected during the TFI period, the pilot gas valve will de-
energize. The control will then go through an inter-purge delay
before an additional ignition attempt. The control attempts two
additional ignition trials before de-energizing the pilot gas valve
and entering lockout. The LED will indicate the fault code for
ignition lockout.
FLAME FAILURE - RE-IGNITION MODE
If the established pilot flame signal is lost while the burner is
operating, the control will respond within 0.8 seconds by de-
energizing the main gas valve and energizing the spark for the
TFI period in an attempt to relight the flame. If the burner does
not light within the TFI, the pilot gas valve will immediately de-
energize and single try models will enter lockout. On multi-try
models, a new TFI sequence will begin after an inter-purge
delay. Multi-try models perform two additional attempts to light
the burner before de-energizing the gas valves and entering
lockout. If the pilot burner relights, normal operation resumes.
FLAME FAILURE-RECYCLE MODE
With the “Recycle After Loss of Flame" option, upon loss of
flame, the pilot and main gas valves are de-energized and the
control proceeds to inter-purge before attempting to relight the
flame. Multi-try models permit three tries for ignition including
inter-purges. If the pilot burner relights, normal operation
resumes. If the pilot burner does not relight, the control will
enter lockout.
Lockout Recovery
Recovery from lockout requires a manual reset by either
resetting the thermostat, or removing 120 VAC for a period of 5
seconds. On models with automatic reset, if the thermostat is
still calling for heat after one hour, then the control will
automatically reset and attempt to ignite the burner.
MOUNTING AND WIRING
The Series 35-703 control 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 160°F (71°C).
All connections should be made with UL Approved, 105°C rated,
18 gauge, stranded, .054” thick insulated wire. Refer to the
appropriate wiring diagram when connecting the 35-703 to
other components in the system.
CAUTION
All wiring must be performed in accordance with
both local and national electrical codes.
CAUTION
Label all wires prior to disconnection when
servicing controls. Wiring errors may cause
improper and dangerous operation. A functional
checkout of a replacement control should always
be performed.
WARNING
This product uses voltages of shock hazard
potential. Wiring and initial operation must be
performed by a qualified service technician.
WARNING
Operation outside specifications could result in
failure of the Fenwal Controls product and other
equipment with potential for injury to people and
property.
Terminal Designations
Terminal
Description
Quick
Connect
(inch)
PV1
Pilot Valve Power
3/16”
L2
120 VAC (Neutral)
3/16”
L2
120 VAC (Neutral)
3/16”
V2
Valve Neutral
3/16”
L1
120 VAC Input (Hot)
1/4”
MV1
Main Valve Power
1/4”
B. GND
Burner Ground
3/16”
S1
Remote Flame
Sensor
1/4”
