Model G3B Gas burner — Instruction manual
MNG3B Gas 041015
13
4. Check System • Start-up Burner/Appliance
(continued)
Installer/servicer
Should overheating or an emergency occur, immediately:
• Shut off main manual gas valve.
• Shut off power to burner.
NOTICE: Under some circumstances power should remain
on for water pumps or circulating blowers. Determine proper
response before attempting start-up.
If burner fails ignition on several attempts, close gas valve
and use burner blower to purge appliance before restart.
Start-up & operation
Do not start the burner if the combustion chamber contains
residual gas. Allow gas to disperse. Failure to comply could
result in severe personal injury, death or substantial property
damage.
Power ON
Open all manual gas line valves. Turn burner combination gas
valve knob to “ON.” Close the line switch. (If burner does not
follow sequence below, see troubleshooting suggestions on
pages 19 and 20.)
Stand-by
(No call for heat) Control waits for heat call.
Call for heat
Set operating control and all limit controls to call for heat.
The thermostat circuit must be closed and power coming to
control panel L1 and L2 terminals
Burner on
The
motor
starts. The hot surface
ignitor
starts. The motor
centrifugal switch makes.
Pre-purge
The primary control allows 34 seconds for pre-purge and
ignitor warm-up.
Gas valve on
After the pre-purge/ignitor warm-up period, the primary
control activates the
gas valve
(if motor centrifugal switch
is closed). The green “Gas valve on” light turns on.
TFI
The primary control turns off the ignitor within 2 to 6 seconds
after gas valve activation. When the control deactivates the
ignitor, it begins checking for flame signal. If flame is not
detected within 6 seconds after gas valve activation, the
primary control will
lockout
with continuous purge (see
following).
Run period
The burner continues firing during call for heat if the flame
rod (hot surface ignitor) senses flame. The green “Gas valve
on” light remains on during normal running, indicating gas
valve is energized.
Shutdown
When the call for heat ends, the primary control immediately
deactivates the gas valve and blower. The burner returns to
stand-by.
Flame failure
If the primary control loses flame signal during a run period,
it deactivates the gas valve within 2 seconds. The control
restarts the heating cycle, beginning with a 34-second
pre-purge/ignitor warm-up period, then a 6-second trial for
ignition. If ignition/flame sensing is successful, the burner
returns to normal operation. If the attempt is not successful,
the primary control will
lockout
.
Lockout
If the primary control does not sense flame within the TFI
time limit after gas valve activation (6 seconds),
lockout
occurs. The control deactivates the gas valve. The blower
motor continues to run, providing a post-purge of the burner
and appliance.
Reset
To reset after a
lockout
, turn off power to burner or interrupt
the thermostat circuit for at least 45 seconds. Then restore
power (or thermostat circuit). Burner should restart.
Ignition and flame sensing
Ignition
The G3B burner uses a silicon carbide hot surface ignitor
for ignition. The Honeywell S89C primary control feeds 120
vac
power to the ignitor and allows time for the ignitor to
warm up to ignition temperature during the burner pre-purge
period.
Sensing
The S89C primary control uses flame rectification to detect
flame, with the hot surface ignitor acting as the “flame rod.”
Before starting burner, verify:
❏
Burner/appliance installed per appliance instruction manual?
❏
Burner orifice size and air throttle verified against Figure 4, page 8?
❏
Burner/appliance installed per all applicable codes?
❏
Installation site has adequate ventilation openings and vent
system?
❏
Gas supply line in good condition and sized correctly?
❏
All gas line joints sealed with pipe dope listed for use with liquefied
petroleum gases?
❏
Gas supply pressure to combination gas valve checked?
❏
Regulator installed if pressure can exceed 14 inches w.c.?
❏
Air purged from gas line?
❏
Gas piping checked for leaks?
❏
Wiring installed per burner and appliance instruction manuals?