2. The ignition control may also be manually reset, by
turning the thermostat down and back up to previ-
ous temperature setting or removing power (24V) to
IC terminal 24 VAC.
Fault Conditions and LED Key
LED Steady On
Internal control fault
1 Flash
Combustion airflow fault
2 Flash
Flame with no call for heat
3 Flash
Ignition lockout
LED flashes on for ¼ second and off for ¼ second dur-
ing fault condition. Pause between fault codes is three
seconds.
1. If, during the initial call for heat, the air switch con-
tacts are closed for 30 seconds without an output to
the combustion blower, an airflow fault occurs (one
LED flash) and control will remain in this mode.
2. If the airflow switch remains open (or a rollout switch
is open) for more than 30 seconds after the combus-
tion blower output (IND) is energized, an airflow fault
occurs (one LED flash) and control will stay in this
mode with combustion blower on, waiting for airflow
switch (or rollout) to close.
3. If the airflow signal is lost during operation, the con-
trol immediately de-energizes the gas valve and
maintains blower operation. If the call for heat re-
mains and proper airflow is not detected, airflow fault
occurs (one LED flash). If proper airflow is detected
at any time, the normal sequence will begin with
pre-purge.
4. If the main valve fails to close properly at the end of
a heating cycle and a flame is maintained, the com-
bustion blower will continue in operation. If the valve
does close completely later removing the flame sig-
nal, the blower will run for the post-purge period and
shut off.
5. Refer to Table K3 for further LED code
troubleshooting.
HF Sequence of Operation – Two-stage
Operation with Two-speed Controller
Fenwal 35-61 Series Direct Ignition Control with
TR1 Timer Relay Control
When system is powered up 24 VAC will be applied to the
ignition control (IC) terminals 24 VAC/R and to the timer
relay control (TR1). The ignition 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 standby state. The amber light on the
TR1 will be lit indicating it is in the ready position.
Call for Heat
1. Thermostat (controller) (first stage or first and second
stage) closes on call for heat.
2. 24 VAC to is supplied to IC terminal TH, provided
limit switch is in closed position.
3. The control will check that pressure switch contacts
are open (IC terminal PSW is not powered).
4. Combustion blower is then energized at high speed.
5. When the air switch (APS1) closes, a 15 second pre-
purge period begins.
6. At end of pre-purge period, the spark commences
and the first and second stage gas valves are ener-
gized for the trial for ignition period.
7. Burners ignite and cross light, operating at maximum
input rate (manifold pressure 3.5” w.c.).
8. TR1 is powered (terminal 7) simultaneously (SR LED
lit) and begins timing a 90 second warm-up period
while maintaining the combustion blower at high
speed (FR LED lit). The TR1 will maintain this mode
of operation, regardless of status of thermostat sec-
ond stage.
9. When flame is detected by flame sensor, the spark is
shut off immediately and gas valves and combustion
blower remain energized.
10. When the initial timer in TR1 times out, it defaults the
gas valve to low fire and the combustion blower to
low speed and returns control of the operating mode
to the temperature controller. The SR LED turns off
and the MR LED is lit.
11. If the controller is calling for second stage heat TR1
terminal 6 is powered. After a short time delay (ap-
proximately 15 seconds), the system switches the
combustion blower to high speed (FR LED lit) and
the second stage gas valve at 3.5” w.c. manifold
pressure (CR LED lit), provided the high air pressure
switch (APS2) is proved.
12. During heating operation, the thermostat, pressure
switch and main burner flame are constantly moni-
tored by the IC to assure proper system operation.
13. Operation continues on high fire until the second
stage thermostat is satisfied, opening the second
stage contact and de-energizes terminal 6 on the
TR1, turning off the second stage gas valve and re-
turning the combustion blower to low speed.
14. When the thermostat (controller) is satisfied and the
demand for heat ends, the first stage valve is de-en-
ergized immediately, the control senses loss of flame
and a 30 second post-purge occurs (at high speed)
before de-energizing the combustion blower.
Ignition and Operational Failures During a Call for
Heat Result in Lockout of the Ignition Control
1. If flame is lost during an operational cycle, the control
will respond within 0.8 seconds. The spark will be
energized for a trial for ignition period to attempt to
re-light burners and prove flame sensor. If flame is
re-established, normal operation resumes
2. If the burners fail to light or carryover during a trial for
ignition, the control will attempt two additional igni-
VCES-VHC-IOM-1F – VHC-36, -42 & -50
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