Instantaneous Water Heater

CMadatMe

Of an application for a Nortiz Stainless Steel 931 ASME Direct Vent for commerical dishwashing. The unit will handle the GPM and we can provide 180 degree water through the wash cycle. The question that has come up is what happens when the commerical dishwasher goes into rinse cycle and has that quick 5-7 second dump? Will we maintain 180 degree water?

I know you can pipe a recirc line but that defeats the selling point of the unit. Does anyone have an installation like this?

Jack

I have done many of these,

but with Rinnai's, as I represent them. You still need the booster at the dishwasher. That way you can run the water heater at 140 and supply the rest of the kitchen with hot water temps. The booster will then peak the temp the last 40 degrees. Everyone likes to try to eliminate the booster, but with a good pre-heat you can minimize the size and cost of operation of the booster. The reason yu need the booster is that if the water heater is 10' away from the dw, if the unit produces 180f water, by the time it gets to the dw it will no longer be 180...Period!

The rinse cycle is where the "rubber meets the road" with on-demand. Never call it instantaneous, it isn't. Satisfactory rinse operation requires water at both the correct temperature, but also the correct pressure. You will find that if the unit is making hot water for the kitchen faucets and the rinse cycle calls, the unit will respond without issue. If however the unit is in stand-by mode and the rinse cycle calls the unit will see high flow instantaneously, recognize that water is getting thruough at the wrong temp, slow the flow down de-pressurinzing the rinse cycle, it gets control of the flow immediately, re-opens the flow valve and by the time the water heater is happy the rinse cycle is almost done. Ka-boom!

I have had very satisfactory results, but I had a pretty rough apprenticeship in these applications. Rinnai engineering likes to be involved in these designs. How many one/two/three bay sinks, spray systems, lavs, dishwasher make and model (imperative that you understand the flow characteristics). In other words, what is your total load.