Tankless Water Heater and Dishwasher

[Beverley]

I had a tankless water heater installed recently. My dishwasher is shutting down mid cycle because the water coming in is not hot enough due to the delay in heating the water initially. This must be a common problem as tankless systems get more popular. Any suggestions?

 

[Reach4]

This would be an unfortunate work-around: run a little hot water from the kitchen faucet when doing dishes?

 

[Sponsor]

 

[Dana]

There isn't really any way to make the ignition delay short enough to deal with water-sipping appliances that take it in ultra-short burst such as dishwashers and many new clothes washers. The short-cycling of the tankless for tiny draws isn't really great for efficiency either, cutting into the potential energy savings of a tankless.

Installing a recirculation loop would guarantee that water arriving at the dishwasher would always be hot enough, at the cost of more abandoned heat in the distribution plumbing.

Installing a local 1-2 gallon point-of-use electric water heater would work too (taking the tankless out of the equation), at the cost of the water heater's standby loss. High efficiency dishwashers use about 3-4 gallons per load, but in multiple draws, with enough time between draws for even a 1200-1500 watt 1-2 gallon water heater to recover.

For a high efficiency clothes washer it might take 3-4 gallons of local water heater- you'd have to look up the specs on the washer in question.

 

[B. John Henley]

I had a 2.5 gal point of use heater tank installed underneath kitchen sink to supply faucet and dishwasher. I never had the same issue you described, but can imagine the point of use heater would be a good fix for you. The 2.5 gal tank is supplied by the hot side from the main house tankless water heater so recovery is quite quick.

 

[Jadnashua]

This, along with trying to get warm water on a low-flow faucet, are one reason why I do not particularly like tankless systems. Their initial cost, regular maintenance, and dearth of qualified technicians means you really have to want one. Yes, they do work for some people, and for many, they love them. They are not always the least expensive option.

 

[Stuff]

If shutting down does that mean it is then heating the water itself or aborting the wash cycle?