5-3
TROUBLESHOOTING
SL 26-260 G3, SL 40-399 G3 MODULATING GAS BOILERS
5.2.2 Fan
Operating power is provided by means of a separate 120 VAC connector (white/black/
green). Control of the fan is provided via a four lead connector. This connector feeds a
PWM control signal (black wire) from the controller and provides a tachometer signal
(white wire) back from the fan. Unplugging the control connector will cause the fan to go to
high speed and trigger a “Blocked Vent Error” within 6 seconds if the boiler is operating.
LEAD COLOR
FUNCTION
TROUBLESHOOTING
Red
35 VDC Positive power
terminal
Fan will only operate at max.
speed if disconnected.
Blue
35 VDC Negative
power terminal
Fan will only operate at max.
speed if disconnected.
Black
Signal from controller
Fan will only operate at max.
speed if disconnected.
White
Fan tach.
2 pulses/rev (freq x 30=rpm)
5.2.3 Water Pressure Sensor
The water pressure sensor ensures that there is adequate pressure in the heating system
for safe operation. The pressure is displayed in PSI as the default. If the system pressure
should drop below 8PSI the firing rate of the boiler is reduced. If the pressure drops to
4PSI or lower, the boiler will not fire.
Check the operation of the sensor by isolating the boiler from its system piping, and close
the system fill valve, and then crack the pressure relief valve. The pressure displayed should
reflect declining pressure. If it remains “fixed”, drain the boiler and replace the sensor, or
dislodge any blocking debris from the sensor inlet channel and reinsert.
5.2.4 Safety and Ignition Module (SIM)
The SIM is a safety control that is certified to conform to the UL 60730-5-5 and ANSI
Z21.20-2014 • CAN/CSA-C22.2 No. 60730-2-5-14 Standards. The low water cutoff
function and the high-limit manual reset water temperature function also conform to these
standards.
The SIM directly controls the boiler’s gas valve and provides:
•
Direct spark automatic ignition
•
Flame detection and current measurement
•
Supply water temperature sensing
•
Flue gas temperature sensing
•
Supply water maximum temperature shutdown
•
Flue gas maximum temperature shutdown
•
Low water cut-off.
Table 10: Fan Operation
