FLAME SENSOR |
| WATER TEMPERATURE SENSORS |
Each burner is equipped with a flame sensor to detect the presence of the burner flames at high and low fire conditions. If no flame is sensed, the gas valve will close automatically. The voltage sensed by the flame sensor will also be displayed on the Burner Screen.
Figure 10. FLAME SENSOR
WATER TEMPERATURE LIMIT CONTROLS
The “XB/XW” models incorporate an outlet water sensor having dual sensors, that are factory set at 210°F (99°C).
MAIN POWER SUPPLY SWITCH
The main power supply switch is a padlockable switch. This switch provides 120V from the power supply to the boiler.
This switch needs to be turned off when servicing the boiler. Note: The Enable/Disable Switch on the front of the boiler does not interrupt electrical power to the boiler.
Figure 11. MAIN POWER SUPPLY SWITCH
Figure 12. WATER TEMPERATURE SENSORS
Temperature sensors are threaded immersion probes. Temperature probes have embedded temperature sensors (thermistors). The boiler’s control system monitors these sensors to determine water temperature at various points in the system.
INLET AND OUTLET TEMPERATURE SENSORS
All models have two inlet and two outlet temperature sensors for each heat exchanger, factory installed to monitor the water temperature entering and leaving the boiler. The Inlet Probe is a temperature sensor only and has two leads. The Outlet probe also contains the manual reset high temperature limit switch and has four leads. The control system displays the Inlet and Outlet water temperatures sensed from these two sensors on the default Temperatures screen.
REMOTE SENSORS
All models are supplied from the factory with a remote sensor. The remote sensor is used to control system water temperature for a single boiler in a domestic hot water storage tank or in the return line from a primary/secondary hydronic heating system.
The boiler will modulate its firing rate in response to the actual system temperature and load conditions. The control system displays the temperature sensed from the remote sensor as the “Lead Lag” temperature on the default Temperatures screen.
LOW WATER CUTOFF DEVICE (LWCO)
Low water cutoff device is normally a closed switch that opens when water drops below a preset level. Each model is equipped with a factory installed LWCO. LWCO board is connected to the electronic panel, whereas the sensor probe is connected to the heat exchanger.
Figure 13. LWCO BOARD AND PROBE
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