Market Forge Industries 2500 HE Service & Parts Manual page 20

5.4.3.1 Improper Polarity
If a spark is present and the gas valve opens but the system
shuts down after the trial period, check the 120 volt a c input
voltage at terminals A (L1) ,and L2 of the control board for
proper polarity Terminal A should be the hot side and L2
neutral with respect to ground.
5.4.3.2 Damaged Grounding
If a spark is present and gas valve opens but the
system shuts down after the trial period, check to make sure
the system is properly grounded to the burner and the
burner itself is properly grounded Proper grounding is
essential for the proof of flame safety device. If the system
is not grounded to the burner, it cannot determine the
presence of flame and will lock out A restart will initiate the
trial for ignition period, but the system will continue to go into
'lock out' if it is not properly grounded, and the thermal reset
will trip. Wait one minute before pushing the IGNITION
RESET button. Check all power and ground terminals to
make sure good contact is made. Clean any corrosion that
might interfere with good electrical contact.
5.4.3.3 Malfunction Due To High Voltage
During the trial for ignition, if the spark is intermittent
and the valve may (or may not) open, check the spark gap
on the electrodes and system wiring as follows:
1. Remove the electrode from the burner and check to see
that the gap is 1/8" ± 1/32". If not, replace electrode.
2. Check the ceramic housing and lead wires for cracks or
breaks.
3. Check terminals E1 and E2 for inadvertent grounding.
They should be at least 1/2" from metal objects which
can cause arcing to ground. If the electrode or lead
wires are faulty replace with new components.
5.4.3.4 Malfunction Of Gas Valve
If the board is receiving proper power and sparking
occurs during the trial for ignition period but the valve does
not open, check the valve for an open coil or other
malfunction. Be sure
Figure 52 Placement of Flume Current Meter
voltage rating of the valve is 120 volts a-c. Use a voltage
tester or voltmeter at terminals B and V2 of the ignition control
board. Voltage should be 120V
5.4.3.5 Erratic Operation
If the system operates properly for a while but randomly
shuts down during the duty cycle, or won't operate during
'cold' starts, check the flame proving circuit with a d-c
microamp meter Refer to Figure 5-2 and proceed as follows:
1. Locate ignition control board (Figure 7-5, 2) 2 Remove low
voltage wire from terminal E2 and connect one lead of
microamp meter to push-on connector attached to lead
wire.
3. Connect second lead of meter to terminal E2 on ignition
control board.
4. Energize control board and read current on microamp
meter. Typical flame current is 2 to 20 microamperes.
If low or marginal flame current is present, it is tripping the
thermal reset switch. If this is the case, relocate the electrodes
or flame sensor into the flame to increase the flame current. If
the ignitor is switched off and on several times in succession,
the thermal reset switch will trip, and it will have to be reset. If
ignition is not achieved after the first two or three attempts,
check to ensure that the other components in the system are
functioning correctly.