Hot Tub Electrical Regulations

Understanding Hot Tub Electrical Regulations can present unique challenges due to the combination of water, electricity, and diverse installation types.

Adhering to specific regulations outlined in BS7671 is critical for ensuring the safety and compliance of hot tub installations. This applies whether they are fixed, hard-wired models or portable types like the popular ‘Lazy Spa’ brand.

Let’s have a look at the key points and what the 18th edition says about them:

Electrical Supply

The type and rating of the electrical supply will depend on the hot tub in use. Broadly speaking, there are 2 distinct types which have their own requirements.

• Portable spas, which are designed to be drained and can be moved, in almost all instances work off a simple 13A BS1362 plug and socket arrangement. Whilst these still present the same safety issues, unfortunately there is much less ‘control’ over their use, electrically speaking. Despite the best efforts of electricians, these are often plugged into extension leads which give rise to their own dangers.
• Fixed spas, which are not designed to be moved, are generally hard wired to a dedicated supply circuit. This is often (although not always) a 32A single phase circuit. The type of cable used will be dictated by the installation method, although due to the usual location, it is often wired in SWA (Steel Wire Armoured) cable. A local isolator will be required, and again, mostly due to the location this would be a >32A rotary isolator.

Earthing Arrangements

Hot tub installations pose a particular challenge around whether PME/TN-C-S earthing arrangements are suitable and can be used for the supply circuit.

In a large number of modern properties, the supply earthing arrangement is often PME (Protective Multiple Earthing), whereby the neutral conductor provides the function of both protective earth & neutral. This is split apart in the supply service head, however these type of installations can be subject to issues where the supply neutral is lost.

In other types of earthing arrangement supplies (typically TN-S or TT), if the supply neutral is damaged or broken for any particular reason, the supply will usually cease to work, both indicating the presence of a fault and also not presenting any further danger.

In scenarios where PME/TN-C-S systems are used, loss of supply neutral can present a particular danger whereby items which are connected to the main earthing terminal form part of the neutral return path (in the absence of a ‘proper’ supply neutral from the grid). This type of fault can often occur without the user being immediately aware, as any appliances will often continue to work (to some extent).

This type of fault creates a need to mitigate risks associated with potential neutral failures, which could result in live conductive parts.

For enhanced safety in hot tub installations, particularly where PME/TN-C-S systems are in place, a TT (Separate Earth) earthing arrangement with earth rods might be recommended. This configuration provides a dedicated local earth path, reducing the risk of electric shock and ensuring compliance with BS7671 regulations.

Installation Guidelines and Compliance

Proper location and bonding of hot tub installations are essential for safety and compliance. Electricians should follow Regulation 701.32 in BS7671, which provides guidance on zoning and protective measures for electrical installations near hot tubs. It’s crucial to ensure that hot tubs are suitably protected from environmental conditions and that all electrical components are adequately bonded.

RCD (Residual Current Device) protection is mandatory for hot tub circuits to safeguard against electric shocks. According to Regulation 702.411.3.3 in BS7671, all circuits supplying a hot tub must be protected by an RCD with a maximum operating current not exceeding 30 mA. This ensures rapid disconnection of the power supply in the event of an electrical fault, minimizing the risk of electric shock.

Conclusion

Adhering to BS7671 regulations is fundamental in ensuring the safety and compliance of hot tub electrical installations. By understanding the specific requirements related to earthing arrangements, bonding, and protection, electricians can confidently install and maintain hot tubs while prioritizing safety.