INSTALLATION AND OPERATION INSTRUCTIONS
5-6
SFT 199 TANKLESS WATER HEATER
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
• Switch on the unit by touching just above the power LED and
holding for 2 seconds.
5.4.2 No domestic hot water (DHW)
POSSIBLE CAUSES ANALYSIS POSSIBLE SOLUTION
The power LED is not shown. → Yes
↓No
• Check the power supply.
• Check the fuse (see electrical schematic).
Flow sensor does not work. → Yes
↓No
Replace the ow sensor.
Domestic hot water ow < 0.5 gpm → Yes
↓No
Increase the domestic hot water ow.
Domestic hot water sensor S3 is
defective.
→ Yes
↓No
Replace the domestic hot water sensor S3.
No electricity on the ow sensor (5V
DC).
→ Yes Check the wiring according to the schematic. CK THE
WIRING ACCORDING TO THE SCHEMATIC.
5.4.3 Domestic hot tap water does not reach the correct temperature
POSSIBLE CAUSES ANALYSIS POSSIBLE SOLUTION
Domestic hot water ow is too high. → Yes
↓No
Reduce the domestic hot water ow.
Setting for domestic hot water
temperature is too low.
→ Yes
↓No
Increase the domestic hot water temperature.
Insuf cient heat transfer due to calcium or
contamination in the domestic hot water-sided
central heating unit.
→ Yes
↓No
De-calcify or ush the domestic hot water-sided central
heating unit.
The central heating system becomes
warm while running hot water.
SFC only
→ Yes
↓No
Undesirable circulation during domestic hot water demand
in the central heating circuit due to thermo-siphon of the
second pump in the central heating circuit. Place a check
valve (in the case of thermo-siphon) or a two-way valve (if
there is a second pump).
The fl ue is blocked.
→ Yes Check the ue.
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