Thermostat Overheat - Keston Celsius 25 Installation And Servicing Instructions

WD209/1/2000

THERMOSTAT OVERHEAT

Is modulation LED1 lit?
Is modulation LED2 lit?
Is modulation LED3 lit?
AFTER ANY THERMOSTAT OVERHEAT IS ACTIVATED THE BOILER WILL NOT RESTART OR CLEAR THE ERROR DISPLAY
UNTIL THE UNIT IS RESET MANUALLY BY TURNING THE BOILER OFF THEN ON BY THE USER CONTROL KNOB.
Installation & Servicing Instructions
Chapter 5 : Fault Finding
Is flow overheat thermostat
open circuit when flow
temperature is < 60
Check system for blockage
and/or air lock. Reset lockout
by turning user knob off then
on. Check pump is operating.
Replace cabinet thermal
fuse and check all
Y
combustion area joints for
leaks.
Reset flue overheat
thermostat. Does flue
temperature exceed 90
Y
when boiler is running at
maximum temperature?
Check gas rate, burner
pressure, combustion levels
and flue and air systems.
SERVICE BOILER
The Keston Celsius 25 & 25P
Replace flow overheat
Y
O
C?
Replace flue overheat
O
C
thermostat.
thermostat.
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