MOUNTING AND WIRING
The Series 35-61 is not position sensitive and can be mounted
vertically or horizontally. The case may be mounted on any surface
with #6 sheet metal screws. All wiring must be done in accordance
with both local and national electrical code.
Power Up /
Stand By
Upon applying power (24 volts) to 24VAC/R, the control will
reset, perform a self check routine, initiate full time flame
sensing, flash the diagnostic LED for up to four seconds,
and enter the thermostat scan state.
Heat Mode
When a call for heat is received from the thermostat supplying
24 volts to TH/W, the control will check the pressure switch for
normally open contacts. The combustion blower is then
energized and once th pressure switch contacts close, a pre
purge delay begins. Following the pre-purge period the gas
valve is energized and sparks commence for the trial for
ignition period.
When flame is detected during the trial for ignition, sparks are
shutoff immediately and the gas valve combustion blower remains
energized. The thermostat, pressure switch, and main burner
flame are constantly monitored to assure the system continues
to operate properly. When the thermostat is satisfied and the
demand for heat ends, the main valve is de-energized immed-
iately, the control senses the loss of flame signal and initiates
a post-purge period (optional) before de-energizing the
combustion blower.
Failure to Light - Lockout
SINGLE TRIAL MODEL
Should the main burner fail to light, or flame is not detected
during the trial for ignition period, the control will go into lockout.
The valve will be turned off immediately, and the combustion
blower will be turned off following the optional post purge period.
MULTI TRIAL MODEL
Multi-try Models will attempt two additional ignition trials before
going into lockout. The valve relay will be de-energized immed-
iately, and the combustion blower will be turned off following the
optional post purge period.
Recovery from lockout requires a manual reset by either
resetting the thermostat or removing 24 volts for aperiod of
5 seconds.
If the thermostat is still calling for heat after one hour the control
will automatically reset and attempt to ignite the burner again.
Flame Failure - Re-Ignition
If the established flame signal is lost while the burner is
operating, the control will respond within 0.8 seconds. The HV
spark will be energized for a trial ignition period in an attempt to
relight the burner. If the burner does not light the control will de-
energize the gas valve. Multi-try models will make two more
attempts to relight the burner. If the burner does not relight the
control will go into lock out as noted above in “Failure to Light”.
If flame is re-established, normal operation resumes.
Combustion Airflow Problems
-
Lockout
Combustion air flow is continually monitored during an ignition
sequence by the air flow switch (PSW). If during the initial call for
heat the pressure contacts are in the closed position for 30 sec
onds without an output to the Combustion Blower, an air flow
fault will be declared and the control will remain in this mode with
the combustion blower off.
If the air flow switch remains open for more than 30 seconds
after the combustion blower output (L1 & IND) is energized, an
air flow fault will be declared and the control will stay in this
mode with the combustion blower on, waiting for the air flow
switch to close.
When proper air flow is detected from the air flow switch input
(PSW) the control begins the prepurge period with a normal
ignition sequence following.
If the air flow 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, the control will
wait for proper air flow to return. If proper air flow is not detected
after 30 seconds an air flow fault signal will be declared. If proper
air flow is detected at any time, a normal sequence will begin
with the prepurge period.
Flame Fault
If at any time the main valve fails to close completely and
maintains a flame, the full time flame sense cir cuit will detect
it and energize the combustion blower. Should the main valve
later close completely removing the flame signal, the combustion
blower will power off following the optional post purge period.
Fault Conditions
The LED will flash on for 1/4 second, then off for 1/4 second during
a fault condition. The pause between fault codes is 3 seconds.
SEQUENCE OF OPERATION / FLAME RECOVERY / SAFETY LOCKOUT
Error Mode
Internal Control Failure
Air Flow Fault
Flame with No Call for heat
Ignition Lockout
LED Indication
Steady on
1 flash
2 flashes
3 flashes
Page 2
35-61, 24 VAC DSI Control with Blower Relay
www.fenwalcontrols.com
1-800-FENWAL-1
WARNING:
The Series 35-61 uses voltages of shock hazard potential. Wiring
and initial operation must be done by a qualified service tech-nician.
The control must be secured in an area that will experience a
minimum of vibration and remain below the operating temperature of
160ºF. All connections should be made with UL approved 105ºC rated
18 gauge, stranded, .054 thick insulated wire. Refer to wire diagram when
connecting the Series 35-61 to other components in the system.
