Abstract: An electric pipe thawing apparatus for thawing frozen water pipes by passing electric current therethrough incorporates various safety feature rendering the apparatus fail-safe in operation. The apparatus includes an A.C. generator from which can be obtained through a step-down transformer arrangement various voltage levels, from 12 volts upwards, for applying low voltage high current power to the pipe to be thawed. One important safety feature prevents the application of a higher voltage to the pipe unless at a lower voltage level, for example, 20 volts, it has been established by measurement that the current flow in the pipe is above a predetermined level and consequently the circuit through the pipe is a good one. If the circuit is not good, when the operator switches to a higher voltage level a danger signal is illuminated.

Abstract: Apparatus for heating pipes and particularly for thawing frozen pipes is disclosed. The apparatus may be a self contained trailer having a generator and step-down transformer. One pair of terminals is connected to the secondary of the transformer and a pair of bus bars is also connected across the secondary. A current transformer operates a warning system indicating that the current to the first terminals is above a maximum value. This warns the operator that another pair of cables is necessary to heat effectively the pipe.