Accu-Steam™ G2 Gas Service Manual
PAGE 22
SP8042-1609
Ignition System Testing
When trouble shooting ignition problems it is absolutely imperative to start off by
taking incoming/outgoing gas pressure and to get a reading from the flame sensor. These
three measurement are the most useful readings a technician can take when diagnosing
AccuTemp gas equipment and are often the most neglected.
Flame Sense
The ACCU-STEAM G2 gas griddle has a flame sensing circuit to determine if the system has proper
combustion. When the system is turned on gas is sent to the burner and an electronic ignition tries to ignite
the griddle. The griddle then checks to see if flame is established in the burner. If the flame sense feedback is
within the proper range the system will stay on until the digital temperature controller is satisfied. The griddles’
ignition module continues to monitor the voltage and as long as its within the proper range the griddle will stay
on. If the flame sense reading falls below the threshold (
13mV or .32uA
) the griddle will go into lock out and
will stop heating. When a lock out occurs, the fault indicator light should illuminate.
Micro-amp flame sense reading
A meter with micro amp (<A) selection or a micro amp adapter must be place in series with the orange flame
sense wire. To check micro amps, disconnect the orange wire from the flame rod and connect the amp meter in
series by attaching one lead of the meter to the flame sense rod terminal and the other lead to the orange wire.
Millivolts flame sense reading
An Accutemp volt-measuring adapter P/N FT0003 (meter set for millivolts) is placed in parallel with the orange
flame sense circuit. To check millivolts, attach one end of the adapter to the orange wire and the other to ground.
If the burner is lighting, determine if the sensing signal level is 30mV (1.38uA) or higher.
A. If the reading is less than 30mV (1.38uA), check for proper gas pressures to the dual valve. For natural gas,
the pressures must be 5” water column for the main gas valve. For propane gas, the pressures must be 10” water
column.
B. If the gas pressures are good but the sensing signal level is still poor, check burner orifice for obstruction.
Clean or replace as necessary.
C. If the gas pressures are good, the pilot orifice is clean, the burner surface is glowing orange to bright orange
but the signal level is still poor, clean or replace the flame sense probe.
Four types of meter readings are possible:
1)
0 millivolts or micro amps
– Look for an open or grounded sensor wire or flame rod,
or a defective ignition module. The wire and rod can be diagnosed with an ohmmeter.
2)
Steady 30 DC millivolts or 1.38 micro amps or higher
– The system is operating within normal parameters.
3)
Fluctuating meter reading
– Check that the flame sensor probes are properly located. Also check for drafts
that can cause an unstable flame. A dirty orifice can also cause an unstable flame.
4)
Less than 30 millivolts or 1.38 micro amps
– Verify the flame-sensing rod is properly engulfed in the flame.
A flame sensor probe too close to the tile will not be in the proper part of the flame, with not enough ionized gas
to allow a proper signal level to be conducted. Conversely, the same thing holds true if the flame sensor
is too high. Also check the ground connection back to the ignition module. Check that the flame-sensing rod and
ground plane are not oxidized. Clean both with a non aluminum oxide abrasive.
