FAULT DETECTING CIRCUITS FOR ELECTRIC HEATERS, PIPE HEATERS AND PIPE HEATING SYSTEMS INCLUDING FAULT DETECTING CIRCUITS AND METHODS OF INDICATING THAT AN ELECTRICAL ENERGY SUPPLY TO AN ELECTRIC RESISTANCE HEATER HAS BEEN INTERRUPTED

摘要

A fault indicating circuit for an electric heater has a first branch to conduct a supply of electrical ,energy to the electrical heater and includes a temperature sensitive device to interrupt the supply of electrical energy to the electric heater when exposed to a temperature exceeding a set temperature. The fault detecting circuit has a second branch that includes at least an element of a fault indicating device. The first branch has a first resistance R₁, the second branch has a second resistance R₂ and the two branches are, electrically in parallel. The first and second resistances R₁, R₂ are such that when, in use, the temperature sensitive device operates to allow : electrical energy to flow through the first branch and the fault indicating device is inactive and when the temperature sensitive device operates to interrupt that supply of electrical energy the fault indicating device activates to indicate that the temperature sensitive device has operated to interrupt the supply of electrical energy to the electric heater.