Effective: March 2020
2F-35-70
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 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 gas valve remains energized. The
thermostat and burner flame are constantly monitored to assure
proper system operation. When the thermostat is satisfied and
the demand for heat ends, the gas valve is immediately de-
energized.
Failure to Light - Lockout
SINGLE TRIAL MODEL
Should the burner fail to light, or a flame is not detected during
the TFI period, the 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 burner fail to light or the flame is not detected during
the TFI period, the 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 gas valve and entering lockout.
The LED will indicate the fault code for ignition lockout.
FLAME FAILURE - RE-IGNITION MODE
If the established flame signal is lost while the burner is
operating, the control will respond within 0.8 seconds by
immediately energizing the H.V. spark for the TFI period in an
attempt to relight the flame. If the burner does not light within
the TFI, the 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 valve and entering lockout. If the burner
relights, normal operation resumes.
FLAME FAILURE-RECYCLE MODE
With the “Recycle After Loss of Flame" option, upon loss of
flame, the gas valve is 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 burner relights, normal operation resumes. If the 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 35-70 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 35-70 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
Multi-Pin
Connector
P/N: TE 1-644615-1
Quick
Connect
(inch)
NC Alarm 11 1/4”
V1 Valve Power 10 3/16”
L2 120 VAC (Neutral) 8 3/16”
V2 Valve Neutral 7 3/16”
L1 120 VAC Input (Hot) 6 1/4”
B. GND Burner Ground 2 3/16”
S1 Remote Flame
Sensor 11/4”
FC+, FC- Flame Sense
Tes t Point s
2 Pin Header
(TE P/N: 640383-2,
Molex P/N: 26-60-2020)
