INSTALLATION AND OPERATION INSTRUCTIONS
5-8
SFC COMBI BOILERS SFC-99, SFC-125
5.4 OTHER FAULTS
5.4.1 No heat (central heating) fault codes
POSSIBLE
CAUSES
ANALYSIS
POSSIBLE SOLUTION
The power LED is not
shown.
→ Yes
↓No
•
Check the power supply.
•
Check the fuse (see Electrical schematic).
•
Check wiring for breaks.
The right display
shows a line (–).
The unit is off.
→ Yes
↓No
•
Switch on the unit by touching just above the power LED and
holding for 2 seconds.
Room thermostat /
weather-dependent
control is not
connected
or is defective.
→ Yes
↓No
•
Check the wiring.
Check the OpenTherm, On/Off connection of the unit, or the
connection between the central heating unit and the
OpenTherm room thermostat. Replace the thermostat.
•
Replace the weather-dependent control.
No electricity (24V).
→ Yes
•
Check the wiring according to the schematic.
•
Check Connector X13.
5.4.2 Central heating does not reach the correct temperature
POSSIBLE
CAUSES
ANALYSIS
POSSIBLE SOLUTION
Water pressure in the
system is too
low.
→ Yes
↓No
Top up the system.
Room thermostat is not
calling for heat.
→ Yes
↓No
Check the setting and adjust it if necessary.
Temperature is set too
low.
→ Yes
↓No
Increase the central heating temperature (see central heating
demand). If an outdoor sensor is present. Check the outdoor sensor.
No flow in the system.
→ Yes
↓No
Check the ΔT ±36°F / ±20°C between the central heating supply and the
return. Ensure a correct flow in the system.
The unit’s capacity is
not correctly
set.
→ Yes
↓No
Adjust the unit’s capacity.
No heat transfer due to
contamination in the
central heating
unit/system.
→ Yes
↓No
Flush the central heating unit/system from the central heating side.
Flue and/or air supply
duct is blocked.
→ Yes
Check and (if necessary) clean the flue and the air supply duct.
