Can MC Cable Come Out of the Wall to Connect a Water Heater?
A user asked the app whether MC cable can exit a wall and run exposed to a water heater. Yes. NEC 2023 Section 330.10(A) permits Type MC cable in exposed work, and a short exposed drop to a water heater is one of the most common legitimate uses of the product. The details that make it pass inspection are support, fittings, and protection from damage.
The rules on the run
Section 330.30 requires MC cable to be secured within 12 inches of every termination and supported at intervals not exceeding 6 feet. For a typical drop out of the wall to the top of a tank, that means a strap within 12 inches of the box or plate where it leaves the wall and another within 12 inches of the water heater connection, with the exposed run following the surface of the wall per 330.15 where practicable. Use listed MC connectors at both ends; the anti short bushing is not an NEC requirement for MC the way it is for AC cable, but most manufacturers supply them and inspectors like to see them.
Physical damage is the judgment call. Section 330.12 prohibits MC where subject to physical damage. A water heater in a garage bay where vehicles or stored gear can hit the cable may push the inspector to ask for protection, a deeper corner location, or a short piece of raceway as a sleeve. In a utility closet or on a basement wall, exposed MC is routine. If the heater sits in a garage, remember the appliance ignition source elevation rules come from the plumbing and mechanical codes, but your cable routing should stay clear of the vehicle envelope regardless.
Connection and sizing notes
A standard 4500 watt residential electric water heater is a 240 volt fixed appliance treated as continuous load under Section 422.13, so the branch circuit is sized at 125 percent: 4500 divided by 240 is 18.75 amps, times 1.25 is 23.4 amps, which lands on a 25 or 30 amp circuit with 10 AWG copper, MC 10-2 being the standard choice. The disconnect rules in 422.31 apply as well: the breaker can serve as the disconnect if it is within sight of the heater or capable of being locked in the off position with a listed lockout device that stays on the breaker. Many installers whip the last couple of feet in flexible metal conduit for service loop flexibility, but straight MC to the heater junction box is fully compliant.