What are the safety rules for floor heating in wet areas such as a bathroom?

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Bathroom Underfloor HeatingIf floor heating is to be installed in a bathroom, the following is important:

The thermostat as well as isolator or plug must be positioned at least 600 mm away from bath-tub or shower-pan (Zone 3). [box type=”info”]Best practice is to locate the isolator for the electric underfloor heating system on the outside of a bathroom.[/box]


  • The system must be properly earthed, and all metal objects in the bathroom like taps etc. must be interconnected to that same earth (equipotential bonding).
  • The system must be connected through an RCD (residual current device) rated at 30mA or less
  • Although legal, the heating will not have much effect under a bathtub
  • The heating element must have an earth sheath (all Coldbuster™ heating elements do).
  • The cold tails must be screened, double insulated or run in a conduit.


Underfloor Heating Electrical Connections and Certificate of Electrical Compliance?

If you install less than 3 kW, you do not normally require a separate circuit.

Power may be supplied from a plug, or the heating may be connected onto a 32 amp ring circuit with the use of a switched fused spur for under 3kw. Anything above that must be run on its own circuit.

Heaters not connected via a socket and plug have to be connected through a double pole isolator as they are considered fixed appliances.

Installation of the isolator and connection to the supply must be done by a qualified electrician.

Top Tip: Fit a wireless receiver/ relay box and make all connections outside of the bathroom, and have a wireless thermostat conveniently positioned in the bathroom for maximum control.  It’s safe to drop the battery powered thermostat in the water but not recommended (you may ruin it)!