59
GAS-FIRED BOILER Boiler Manual
PART 12: TROUBLESHOOTING (CONTINUED)
Table 12-1 : 926 Control Board ERROR Codes
Code Description Corrective Action
Fou
Outside sensor shorted or
temperature less than -40
Degrees Fahrenheit
Inspect wiring from outside sensor for damage or shorted connections repairing as necessary.
Measure resistance of outdoor sensor and compare to resistance chart. If not within range on
chart, shorted or open, replace sensor
E19
Line voltage frequency
out of range.
Inspect power wiring to boiler and repair as necessary. If connected to line voltage, notify power
company. If connected to alternate power source such as generator or inverter make sure line
voltage frequency supplied by the device is 60 Hz
HIO
Condensate error.
1. Check condensate lines for obstructions
2. Check float switch in condensate reservoir.
3. Check wiring from condensate reservoir to 926 control and repair as necessary
Flu
Blocked vent pressure
switch
1. Assure that the vent is not blocked
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 unit
WARNING: Do not use jumper to remedy this error. Faulty switch 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 boiler system.
2. Be sure all air is bled from the 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 as necessary
LOU
24 volt low
1. Check line voltage. Must be between 100-128 volts.
2. If available, connect 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 code 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 boiler is so equipped, dis-
connect high gas pressure switch, then low gas pressure switch, then UL 353 low water cut-
off in this order one at a time to see if LOU code clears. Replace faulty part. Check low volt-
age wire harness in boiler 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, re-
place the 926 control board.
EO3
System sensor failure
(Cascade Master only)
1. Check wiring to system sensor. Repair as necessary
2. Check sensor resistance. Compare to the table in Fig. 12-4. Replace if not correct.
FL
Low water flow
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.
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