METHOD AND APPARATUS FOR CONTROLLING SYSTEM WHEN COMPLETELY FREEZING GAS BOILER

摘要

PURPOSE: A method is provided to judge the complete freezing of a boiler with two thermistors and to protect a system by stopping the system. CONSTITUTION: A system for a gas boiler is controlled by the steps of; detecting a state lower than the freezing point with low temperature thermistors; driving a circulating pump during a specific time; sensing that there is no change in temperature between the first and second thermistors during a specific time; outputting an answer signal to a three-way valve to confirm the drive of the three-way valve; and working the system in an error mode without starting the system by deciding the complete freezing of the system if there is no answer signal.