Point Of Use Tankless for Sink and Dishwasher

[IronDevil74]

Hi,

I am looking for help picking a point of use electric tankless unit for my kitchen sink and dishwasher. Here are some details about my situation:

Main hot water heater is a Rheem 200k BTU gas unit. Works great. Produces lots of hot water.

But, that unit is 45-60ft (pipe distance) from the kitchen sink. So, it takes a long time for hot water to reach the sink. My main concern is that when the dishwasher goes to the rinse cycle, the water in the line is cold, so the dishwasher doesn't ever get the full temp hot water. For the wash cycle, i pre-run the sink to get the hot water there for the wash cycle.

So, I want to put in one of these small point of use electric hot water heaters. Ideally, I would like to install it on the hot water line so that it shuts off when the inlet hot water from he main unit reaches the right temp.

I am having a new 200 amp panel and service installed and I had an 8 gauge 240 line run from the panel to the sink during an earlier remodel. So, I am hoping I am ok for whatever size unit I need.

Any input on what I am trying to do and recommendations on a good unit for this application would be really appreciated.

Thanks,
Charles

 

[Dana]

A point of use electric tankless is pretty expensive to install due to the fat wiring it takes to have enough capacity to do the job. A cheaper solution would be to install a 3-5 gallon tank-let, and feed it with the output of the main water heater. Even 60 feet of 3/4" copper has only 1.4 gallons, so even with dilution factor of the initial slug of room temp water the average temp in a 3 gallon tank stored at 130F won't drop below ~110F before the water from the main water heater arrives.

 

[Sponsor]

 

[IronDevil74]

The fat wire (8 gauge) is already installed and the 200amp panel is going in anyway. My concern is not the temp of the water when it gets to the sink. My concern is that when the dishwasher fills for the rinse cycle - probably less than 2 gallons - it is filling with room temp water, not hot water.

 

[Jadnashua]

8g is good for a 40A circuit. Code says a 40A circuit with something like a WH on it can use a maximum of 32A (80% rule applies). 32A*240v=7680W, which equals 26.5KBTU. IOW, not a whole lot! A good tankless system that can heat water quickly is often in the 199K BTU rang, or about 8x as much. You'd be much better off with a small tank, as 8g won't get you much of a tankless system and will be LOTS cheaper to buy and install.

 

[Ladiesman217]

The fat wire (8 gauge) is already installed and the 200amp panel is going in anyway. My concern is not the temp of the water when it gets to the sink. My concern is that when the dishwasher fills for the rinse cycle - probably less than 2 gallons - it is filling with room temp water, not hot water.

Why waste your time and money on a point of use water heater if the dishwasher is your only concern?

Just use the water preheat option in your dishwasher. You only need "hot water" for the wash cycle. Your dishes could care less about the temperature of the water used in the rinse cycle.

If you do not have the water preheat option, buy a new dishwasher instead of a point of use water heater that produces water that may not be hot enough!

http://reducingenergy.blogspot.com/2008/08/preheat-dishwasher-water.html