68
If overheating occurs, or the gas supply fails to shut off, do not turn off electrical power to the circulating
pump. This may aggravate the problem and increase the likelihood of boiler damage. Instead, shut off the
gas supply to the boiler at the gas service valve.
926 CONTROL BOARD ERROR CODES
CODE
DESCRIPTION
CORRECTIVE ACTION
FOU
Outside sensor shorted or
temperature less than -40
degrees F.
Inspect wiring from outside sensor for damage or shorted connections. Repair as
necessary. Measure resistance of outdoor sensor and compare to resistance chart. If not
within range of chart, shorted or open, replace sensor.
E19
Line voltage frequency
out of range.
Inspect power wiring to appliance and repair as necessary. If connected to line voltage,
notify power company. If connected to an alternate power source, such as a generator or
inverter, make sure line voltage frequency supplied by the device is 60 Hz.
FLU
Blocked Vent Pressure
Switch
1. Check the flue vent to be sure it is not blocked or damaged.
2. Check the switch wiring by applying a jumper in place of the switch. If the code clears
with the jumper in place, REPLACE the flue switch and connect the wires to the new switch
BEFORE running the boiler.
WARNING: Do not use jumper to remedy this error. Faulty switches MUST be replaced.
Failure to do so could result in serious injury or death.
LEO
Water Level in Boiler is
Low
1. Check boiler feed water system to be sure it is supplying make-up water to the boiler
system.
2. Be sure all air is bled from system.
3. Check for leaks in boiler and system piping and repair as necessary.
4. Inspect low level switch and wiring for damage and repair if necessary.
LOU
24 Volt Low
1. Check line voltage. Must be between 100 – 128 volts.
2. If available, connect a PC and, using HTP service software, check the 24v supply display
in the lower left corner of the screen. The number displayed here must be greater than 128
and should be greater than 250. Use this as a troubleshooting guide as you follow the steps
below.
3. Remove 10 pin Molex connector from customer connection board. If LOU clears, then the
problem is with external sensor wiring. Examine external sensor wiring for shorts to ground,
repairing as necessary. If LOU code is still present and the heater is so equipped,
disconnect high gas pressure switch, then low gas pressure switch, then UL 353 low water
cutoff in this order, one at a time, to see if LOU code clears. Replace faulty part. Check low
voltage wire harness in heater for shorts to ground.
4. If LOU only occurs when burner tries to light, check gas valve for excessive current draw.
5. If LOU is present with the low voltage harness disconnected from the 926 control board,
replace the 926 control board.
E03
System sensor failure
(Cascade Master only)
1. Check wiring to system sensor. Repair as necessary.
2. Check sensor resistance. Compare to the resistance table in this manual. Replace if not
correct.
FL
Low water flow (Users
with optional flow switch
only).
1. Check to see if boiler circulator is functioning. Repair as necessary.
2. Be sure water is flowing in the system. Check for valves that should be open, plugged
filter screens, etc.
3. Check flow switch and wiring. Repair as necessary.
Table 18
926 Control Board FAULT
Codes
Description
Remedy
F00
High temperature limit
exceeded
1. Check circulation pump operation.
2. Assure that there is adequate flow through the boiler by accessing the status menu
and assuring that there is less than a 50
o
F rise from the return thermistor to the supply
thermistor.
3. Check thermistor reading on supply thermistor. Replace switch if faulty.
4. Disconnect the two wires from the thermostat terminals and connect the wires
together. Depress the
S4/Reset
button. If the fault clears, the problem is outside the
boiler.
Summary of Contents for Mod Con 300 HL
Page 13: ...13 Figure 2 ...
Page 31: ...31 Figure 13 ...
Page 37: ...37 J SIDEWALL VENTING DIAGRAMS Figure 16 Sidewall Venting with Tee and Coupling ...
Page 38: ...38 Figure 17 Sidewall Venting Diagrams ...
Page 39: ...39 K VERTICAL VENTING DIAGRAMS Figure 18 Two Pipe Roof Venting with Tee and Coupling ...
Page 40: ...40 Figure 19 Roof and Sidewall Venting with Stainless Steel ...
Page 44: ...44 E GAS VALVE Figure 21 ...
Page 45: ...45 Figure 22 ...
Page 55: ...55 Figure 28 Mod Con Internal Connection Diagram ...
Page 73: ...73 Figure 32 ...
Page 74: ...74 Figure 33 ...
Page 75: ...75 Figure 34 ...
Page 76: ...76 Figure 35 ...
Page 77: ...77 Figure 36 ...
Page 80: ...80 ...
Page 81: ...81 ...
Page 82: ...82 MAINTENANCE NOTES ...