IBC Technologies VFC 160 Installation And Operating Instructions Manual - page 18
IBC Technologies Inc.
- 18 -
VFC 160
3. MAINTENANCE AND TROUBLESHOOTING
3.1 BOILER OPERATION
3.1.1 Normal Operation
1. On power-up, the boiler exercises the
fan and pump by entering into a post-
purge routine - see below.
2. On a call for heat, the blower and
pump switch on.
3. After 20-40 seconds, the gas valve
opens and the igniter probe sparks.
The ignition module will issue a spark
to the burner for approximately 10
seconds. If no flame is present, the gas
valve closes, and locks out until there
is a new call for heat.
4. On successful ignition, the spark is
discontinued and the gas valve remains
open.
5. If water or vent temperature conditions
exceed safe operating limits, or vent
pressure falls below the calibrated
value, the gas valve closes and the
burner remains off until a safe
condition exists. A post-purge cycle
follows.
6. If the call for heat ends, the gas valve
closes and the boiler will enter a post-
purge cycle.
3.1.2 Post-Purge Cycle
The post-purge cycle employs the variable
speed fan to clear exhaust gases from the
boiler and its venting, and the pump to
utilize residual heat from the boiler vessel
during cool-down. The fan and pump
provide normal flow rates for an initial 10
second period; subsequently the fan is
commanded to an ultra-lowflow mode for
up to 90 minutes to act as a vent-damper.
The pump maintains normal circulation
throughout the phase. This low intensity
mode is a simple way of ensuring moisture
does not migrate and re-condense around
and above the burner area (e.g. fouling the
igniter) during the off-cycle.
The post-purge is immediately interrupted
by a new call for heat, or return to safe
condition of a tripped limit switch (in the
case of a shutdown caused by an open hi-
limit). In such case the mode ends and the
boiler enters an ignition cycle. The
interrupt is deferred however, to allow a 2
minute low-flow interval prior to return to
the ignition routine in the event of an
opening of the control circuit at the air
pressure switch; this is to allow for
clearance of any excess buildup of
condensates in the vent.
3.1.3 Boiler Safety System
There are 5 safety devices that can cause
the boiler to shut down:
1. Outlet Water Limit: closes gas-valve
when outlet water exceeds 200°F.
2. Vent Hi-Limit: closes gas-valve when
vent temperature exceeds 230°F.
3. Pressure Switch: closes gas-valve
when air pressure drops below 0.9”wc.
4. Flow Switch: Shuts boiler off if water
flow drops below US 4 gpm
5. Flame Presence: the ignition module
will lockout if no flame is detected
during its 21 second trial period.
Causes for this can be found in Section
4 - Troubleshooting Guide under
Lockout.