Source: Beijing Baxi Wall-Hung Boiler Repair http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3778734.
Explanation of the Low Oil Temperature Interlock Protection Function for Baxi Fuel-Fired Wall-Hung Boilers
The low oil temperature interlock protection is a unique safety feature of fuel-fired wall-hung boilers. Since oil temperature has a close relationship with viscosity, when the oil temperature is too low, the viscosity increases, which can affect atomization. Poor atomization makes it difficult to ignite the main burner, leading to multiple ignition attempts that leave excessive residual oil in the combustion chamber, increasing the possibility of a cold explosion. At the same time, poor atomization results in abnormal combustion, causing black smoke from the chimney and may even lead to the boiler suddenly going out.
Therefore, when the oil temperature is too low, the oil temperature control switch prevents the boiler from starting or puts an already running boiler into a pause state until the oil temperature recovers, allowing the system to continue working. When using heavy oil as fuel, the oil temperature should be maintained around 120°C, and a WT-1226B type temperature regulator can be used for interlock protection control. The lower limit temperature of the regulator is set at 75°C, which serves as the low-temperature interlock protection point.
When the oil temperature falls below the specified range down to 75°C, the control switch contacts of the regulator open, cutting off the control circuit, stopping the spraying and combustion process, and putting the boiler into the post-blowing program to shut down, thereby realizing the protective function.