Heat tracing and earth leakage protection
First and foremost, ensure that you install cables in accordance with the manufacturers instructions. Click here for a copy of the Thermon installation instructions.
All the Thermon heat tracing cables have an earth braid (the metallic braid on the outside of the heat trace cable). This is not mechanical protection. Instead it is so the heat trace can have adequate earth protection. All our heat trace cable has this - we do not sell any heat trace that cannot be earthed.
We commonly have questions along the lines of "can we take the braid off the Thermon heat trace cable because it fits better?"
We routinely say from a safety standpoint and based on AS/NZS 3000 4.10.5 additional protection NO.
All heating cables shall be provided with additional protection by an RCD with a fixed rated residual current not exceeding 30mA and –
A in the case of heating units fitted with a conductive covering this covering shall be earthed; and
B in the case of under-floor heating units without a conductive covering an earthed Metallic grid with a spacing not exceeding 30mm shall be provided above the underfloor heating cable.
I have witnessed a freezer door where the cable was damaged and they had an earth tripping fault. Because of this fault, they bridged out the earth protection. We could see scorch marks around the door where the heat trace cable had been arching. We call this a wet fire, and it is caused by water getting into the cable and under the insulation.
Remember: always refer to the wiring regulations and manufacturers instructions. VMS Heat Tracing Ltd does not take responsibility for actions resulting the above information.
For more information on earthing your heat trace cable call Vaughan Skiffington on 021 401 444.