Code Change Summary: New code language from a 2011 Tentative Interim Amendment (TIA) added to 680.42(B) allows perimeter surfaces around certain outdoor hot tubs to remain unbonded.

Bonding the adjacent perimeter surfaces to other nearby metallic components and equipment places everything at the same potential. This ensures protection from stray voltage or voltage gradients in the area around a spa or hot tub.

The perimeter surfaces surrounding an outdoor spa or hot tub are generally required to be bonded in accordance with section 680.26 which is located in part II of Article 680. After the 2011 NEC^® was released, a Tentative Interim Amendment (TIA 11-1) was introduced that created a new provision allowing these surfaces to remain unbonded where ALL of the following conditions apply:

(1) The spa or hot tub is listed as a self-contained spa for aboveground use.

(2) The spa or hot tub is not identified as suitable only for indoor use.

(3) The installation is in accordance with the manufacturer’s instructions and located on or above grade.

(4) The top rim of the spa or hot tub is at least 28 in. above all perimeter surfaces that are within 30 in., measured horizontally from the spa or hot tub. The height of any nonconductive external steps for entry to or exit from the self-contained spa shall not be used to reduce or increase this rim height measurement.

The reason the TIA was originally introduced was because there was no real substantiation as to why the extra bonding measures were needed when a listed package hot tub unit was installed. The idea of a listed package hot tub is not much different than installing a storable pool as allowed in part III of article 680 and in that section, no equipotential bonding of perimeter surfaces is required.

In the 2014 NEC^® the previous TIA 11-1 was incorporated directly into the new code language and is now part of section 680.42(B).

Below is a preview of the NEC^®.  See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).