CT33 User Manual v. X1.0 26
12
Floor heating cables and their faults
12.1 Preliminary inspection of the target area
As a first step it is always recommendable to perform a systematic inspection at the cable assembly area,
assembly method as well as fault type.
Typical reasons to floor heating faults
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Cable has been damaged during assembly. In time heating current has gradually burned the conductors,
resulting in an open or short-circuit fault. There may be several faults in the same cable.
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There is an air pocket in the concrete, causing cable over heating and eventually an open or short-circuit.
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The floor structure has changed, e.g. fallen down, causing cracks and damage to cable.
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Renovation work such as drilling or moving fixed furniture has resulted in a latent or immediate damage.
When and how the fault appeared
- Did it blow a fuse (short circuit)
- Did the cable just stop heating (cut cable)
- Did a residual current device trip (ground leak)
- Has there been renovation or other changes made recently or some time before
Measuring cable resistances and capacitances
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Make sure that cable wires are not live and disconnect all from the feeding cable.
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Measure resistances and capacitances between all heating cable wires and shield and compare them to
normal values of an intact cable (L-N / L-PE and N-PE)
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In case the heating cable is shorted to concrete reinforcement, it is worth measuring all wires against the
building’s earthing too.
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Resistance values usually reveal the fault type and which wires are affected. Capacitances may help defining
the fault distance from the measuring point.
