16
To Enter Installer Mode:
a.  Ensure the slider is in the RUN position, then press and hold 
 and   buttons 
together for 8 seconds. Ignore the ‘NOT VALID’ message that is displayed for a 
few seconds. The message ‘SET UP MENU’ will show briefly, followed by ‘SET 
INSTALLER OK ?’
b.  Press the 
 button to take you into the Installer Mode Parameter Menu.
c.  Parameter 1 is now available to change. This is to allow you to change the 
clock format from 12 hour AM/PM to 24 hour. At every step, the LoT™ Display 
will inform you what the parameter means and what option you have selected. 
The parameter number is shown on the display separated by a colon from the 
parameter value.
d.  You can change the parameter value by pressing the 
   or   buttons. At this 
point the description in the LoT™ Display will change and the parameter value 
will flash. If you press   the value will stop flashing and be saved for use.
INSTALLER 
PARAMETER
Parameter 
Number
Default 
Value
Options Description
Optimum start
9 0 0, 1, 2 0 = no optimum start
1 = delayed start
2 = optimum start on
* Optimum start limit 10 1 1, 2, 3 1 = 1 hour
2 = 2 hours
3 = 3 hours
Optimum stop
11 0 0, 1 0 = disabled
1 = enabled
Frost protection 
temperature
12 5 5 to 
16°C
Frost protection 
temperature
Minimum ON/OFF 
time 
13 1 1, 2, 
3, 4, 5 
mins
Minimum ON/OFF time 
in minutes
Cycle rate
14 6 3, 6, 9, 
12
Number of boiler cycles 
per hour 
Proportional band 
width
15 1.5 1.5 to 
3.0°C 
Width of control 
proportional band in °C 
Failsafe mode (loss of 
RF communications)
16 0 0, 1
0 = off
1 = heating on  20%
Reset all parameters
20 1 0, 1 0 = do not reset
1 = default parameters
FINE TUNING YOUR  ST9420C