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Does an electric water heater require a disconnect?
Wednesday, July 11, 2018
When someone is repairing an electric water heater, they need to be assured that the electricity stays off while they are handling wiring and connections that could shock or kill if the circuit were to suddenly become “live.” So the building code addresses this safety issue by providing several choices of solutions that make the means of disconnecting the circuit either within sight or under the exclusive control of the person working on the water heater.
Here are the four options:
1) Panel within sight - If the main electric panel or a subpanel that serves the water heater is within sight, a second means of disconnect is not necessary. So a water heater that is in a garage or utility room with a direct sightline to the nearby panel serving it would be acceptable.
2) Pull disconnect or circuit breaker panel within sight - This is the solution we see most often in new construction.
3) Wall switch within sight - This is acceptable, but not necessarily the best choice, because eventually someone in the house will use the switch to try to turn on a light in the closet or room. After flipping it back and forth several times, they will decide that the switch doesn’t work, leaving it in the off position. Your next shower will be a cold one unless you label the switch as “WATER HEATER”. If you do choose this option, the switch be 30-amp rated (not a regular light switch).
4) Lockout device at panel - This is a metal gizmo that attaches permanently around the circuit breaker for the water heater in the electric panel, and is used when the panel is not within sight of the water heater. It has a hasp with a hole in it that accepts a small padlock, and allows the circuit breaker to literally be locked into the off position. Only a permanently installed lockout device is acceptable.
By the way, the first three options that are specified as “within sight” mean “within sight in both directions”: the switch should be visible from the appliance and the appliance visible from the switch. So, if the switch is just around a corner from where the water heater is located, and you can see it when standing at the switch, but the switch itself is not visible when you are at the water heater, it’s no good. The NEC also defines the range of “within sight” is maximum 50 feet away.
Prior to the 2017 edition of the National Electric Code, appliances rated at not over 300 volt amps (watts) or not over 1/8 hp motor were required to have a disconnect [NEC 422.31(a)], but it was not clear that it must be within sight if not lockable. The 2017 edition, however, added “where the switch or circuit breaker is within sight from the appliance” to the citation to clarify the intent.
A “cord and plug within sight,” like in the photo below, was once acceptable for water heaters but has not been allowed for at least the past 25 years. The NEC now requires that any appliance that is cord-connected must "be designed to permit ready removal for maintenance or repair,” and the pipe connections at a water heater disqualify it.
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