The insulation resistance test is designed to detect very small breaks in the cable insulation before, during and after installation. These breaks are often not detected during the continuity test, as they do not necessarily constitute short circuits between the conductor and the earth braid. Even small breaks can cause current to leak to earth. Such leakage is usually detected by the mandatory ground fault circuit interrupter (GFCI thermostat or panel-mounted GFCI). When a current leakage is detected, the GFCI breaks the circuit, deactivating the floor heating system. A megohmmeter (sometimes called a “megger”) is a special type of ohmmeter that supplies a high voltage to measure the electrical resistance of insulation. An ordinary ohmmeter or multimeter is not capable of producing the required voltage, and so cannot be used to perform this test.
It features three user-selectable test voltages: 250V, 500V and 1000V. Model 6527 is also a multimeter with an AC/DC voltmeter function capable of measuring up to 600VAC and 1000VDC, a continuity test function with audible signal for resistances below 35Ω, and 600Vrms overload protection. In addition, it can measure resistance up to 400kΩ. The TEST button is associated with a lockout function for continuous tests of up to 15 minutes, eliminating the risk of overload.
