Strebel S-WG 100, Installation, Operating And Maintenance Manual, Page: 105 / 125

E09.012.246 Manual S-WG
106
Display message
F7
F l u e t e m p t o o h i g h
p u m p o n 9 9 9 , 5 h r s
Reason
Flue gas temp. exceeded 3 times limitation value within
a certain period.
Cause:
Heat exchanger polluted and not able to transfer enough heat to system water.
Corrective action:
Check and clean heat exchanger.
Cause:
Bad flue gas sensor or sensor connection (partly shorted).
Corrective action:
The sensor is of the type NTC. This means if the temperature rises the measured resis-
tance is lowered. A partly shorted sensor will drop the resistance and therefore 'measure'
a raise in temperature when actually there is none.
Check for moist in the sensor connections or replace sensor.
Cause:
There is no water in the unit while firing.
Corrective action:
This is an unlikely situation while all the safeties for checking the water presence didn't
detect anything. Only a lot of air in the system/unit (under pressure) can cause the water
pressure switch to switch while no water is present. Also the water leak detection
did not react. Bleed all air from the unit so the heat from combustion can be transferred to
the water and won't leave through the flue system.
Cause:
Heat exchanger failure.
Corrective action:
This is an unlikely situation but when there is severe damage to the heat exchanger, the
combustion product will not be able to transfer all heat to the system water. The heat that
is not transferred will convert to an increased flue gas temperature.