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Does a tankless (on-demand) gas water heater require an electrical disconnect within sight?
Wednesday, June 13, 2018
A tankless gas water heater uses natural or LP gas as fuel, but requires 120-volt electricity for its blower and control panel, so it is required to meet the disconnect standards for a “Permanently Connected Appliance” by the National Electrical Code (NEC). Although it uses much less electricity than an electric water heater, the disconnect must meet the same requirement of being within sight or lockable if not.
The purpose of all of them is to make sure that a technician working on the water heater does not have to worry about being shocked by someone else turning the electricity back on. Manufacturers also specify a disconnect near the water heater in their installation manuals. The diagram above is from a Rinnai manual.
For a full explanation of the disconnect rule, see our blog post What is the NEC disconnect requirement for permanently connected appliances rated at not over 300 volt-amperes (watts) or 1/8 horsepower?
Unfortunately, the requirement for an electric hookup at a tankless water heater is a drawback during a power outage, when compared to an old-fashioned tank gas water heater. See our blog post Does a tankless gas water heater still work with no electricity during a power outage?
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