Method and apparatus for using direct current to detect ground faults in a shielded heater wire

An ice and snow melting system, comprising:

• a heater for melting the ice and snow, said heater including a heater wire, a layer of insulation substantially surrounding said heater wire, and a conductive shield substantially surrounding said layer of insulation;
• a DC power supply configured for applying a DC voltage to said conductive shield;
• and
• a current detecting device coupled with said conductive shield and configured for detecting a DC current associated with said DC voltage in said conductive shield, said DC current flowing from said conductive shield to said heater wire.

A method of controlling a heater used to melt ice and snow, said method comprising the steps of:

• providing the heater with a heater wire, a layer of insulation substantially surrounding said heater wire, and a conductive shield substantially surrounding said layer of insulation;
• providing heater control circuitry for selectively controlling operation of the heater;
• sensing one of temperature and moisture associated with an ambient environment with a sensor and providing a signal indicative thereof with said sensor;
• transmitting said sensor signal to said heater control circuitry;
• applying a DC voltage to said conductive shield without first applying the DC voltage to said heater wire;
• detecting a DC current associated with said DC voltage in said conductive shield;
• transmitting a signal indicative of said DC current associated with said DC voltage to said heater control circuitry;
• and
• selectively controlling the operation of the heater with said heater control circuitry, dependent upon at least one of said sensor signal and said signal indicative of said DC current.

A method of controlling a heater used to melt ice and snow, said method comprising the steps of:

• providing the heater with a heater wire, a layer of insulation substantially surrounding said heater wire, and an ungrounded conductive shield substantially surrounding said layer of insulation;
• applying a DC voltage directly to the conductive shield;
• detecting a DC current associated with said DC voltage in the conductive shield;
• and
• selectively controlling the operation of the heater dependent upon said detecting step.