I am looking at a house that has a "point of use" hot water heaters in the kitchen -- which is a long way from the main hot water heater. This small 6 gallon heater is set to a higher temperature than the main hot water heater and supplies water to the dishwasher. It connects to electric power through a standard outlet on a dedicated circuit. The water supply to this heater is off the hot water pipe to the kitchen sink.
I have never seen this done before, but was told that this was done to insure that the dishwasher would always have hot water when started -- without anyone having to run water until it gets hot. This also lets them set the gas hot water heater at a lower temperature.
Is this arrangement legal, and is a 6 gallon heater really large enough for a typical dishwasher fill? Does this arrangement "waste" energy by maintaining (with electricity) a very small tank of super heated water for use only by the dishwasher?
Interesting questions. In commercial kitchens, 140* is required at the DW. This is usually achieved with a point of use booster or a dedicated 140* kitchen heater with tempering valves set at 120* at all outlets-except the the DW(140)
Some residential dishwashers have built in booster heaters that raise the temp to 140* If yours does- you're DW booster should do the work and wouldn't need the 6 gal htr.
As for legal, it would be OK in my area- if plumbed correctly, including the T&P line
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