I'm looking for information / references on when exactly it is required to ground / bond the steel reinforcement in an exterior concrete pad, and how to do so. The pad I'm planning is for a hot tub / spa in the USA / NY. I am not planning a plastic vapor barrier under the slab so it will be directly in contact with the earth (concrete over gravel over sub-soil).
Initially I was skeptical that grounding the rebar/mesh is necessary since concrete on the ground is literally grounded already. But I get that sometimes bonding is needed to avoid a potential difference and I would like to be safe & follow code.
The most detail I've read so far is quoted below but doesn't cite any code references or other qualifications about when / where its needed.
Extract from forum post noted above:
In my area, this is required.
Technically, the metal in the concrete is "bonded" rather than grounded.
The nuts and bolts procedure is to connect, and provide access to, a ground wire to the metal mesh or rebar within the slab - this wire will be connected to the common bonding point within the spa once it is installed.
To the common bonding point there are a number of wires from / to various locations / items, including but not limited to:
Metal frame of the unit
Motor frames within the unit.
Metal piping from within the unit.
Metal within the pad.
Any other metal within 5' of the spa - downspouts, metallic conduit, gas piping, water piping, handrails, etc.
A ground wire going to the ground bar of the panel which serves to supply the power for the spa. Could be the SEP or a sub-panel.