A.O. Smith BTH 120 - 250 - Manual (Page 17)

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Display Flashes “05” when button is pressed:
Display Flashes “15” when button is pressed:
Display Flashes “25” when button is pressed:
ECO SWITCH OPEN (Figure 22)
ECO LED Flashing:
ECO SWITCH OPEN, ECO LED Flashing
FIGURE 22
CONTROL BAD (Figure 23)
All LEDs Flashing:
Possible Cause Remedy
1. This indicates the control has 1. Press button on the
failed on of its internal display board to reset
diagnostic self-tests. control. If this error
occurs repeatedly,
replace control.
CONTROL BAD, All LEDs Flashing
FIGURE 23
COMBUSTION AIR BLOCKAGE (Figure 24)
Pressure Switch LED Flashing:
COMBUSTION AIR BLOCKAGE, Pressure Switch LED Flashing
FIGURE 24
Possible Cause Remedy
1. Temperature Probe wiring 1. Repair Wiring
open
2. Defective probe 2. Replace probe
Possible Cause Remedy
1. No water in tank and tank 1. The symptom does not
in freezing conditions reflect a control problem
2. Water in tank above freezing 2. Temperature probe out of
tolerance, replace temp.
probe
Possible Cause Remedy
1. Water in tank is low, probe 1. Fill tank
immersed in steam
2. Probe wiring shorted 2. Repair wiring
3. Defective probe 3. Replace probe
Possible Cause Remedy
1. Temp. Probe unplugged 1. Check connectors
2. Temp. probe wiring damaged 2. Repair wiring
3. Water in tank too hot 3. Normal condition when
water t e m p e r a t u r e
exceeds safety limit.
Allow water to cool or
admit water into tank and
manually reset the control.
Determine cause for
overtemp condition.
Possible Cause Remedy
1. Combustion air blocked 1. Check exhaust piping and
flue for obstructions
2. Blower not operating: 2. a. Repair wiring
a. Check blower wiring b. Replace blower motor
b. Check blower motor
3. Defective air switch 3. Replace air switch
4. Pressure switch jumped out 4. This controller must sense
an open contact on the
blower proving airflow
switch before the blower
comes on. Check to see if
blower proving airflow
switch is still connected to
the unit.