My newest dilemma is now mixed.
To begin with I am not tank less water heater person.
I will avoid it where I can, and I only design it when I am forced to with knowledge that the owner, designer, architect made the final decision. Energy wise, the marketing has been great for the tank less water heaters. They are considered Green. Yet the aspect of sustainability, longevity, endurance is not accounted for by this newly advocated green product. It may be a very very light color green, I can assure you it is not a full pledged green.
My issue today meanders over several subjects. Once we are completely done with tank less, issue of insta-hot water heaters and dishwashers will be discussed. Once, the reader is fully concentrated, they will identify how many traps and buried within these issues and they could become a fall person for a litigation procedure.
Back to tank less water heaters, since their inception in this country, their marketing was immaculate. Nicely performed on the auspicious of the lesser area requirements, they hit the soft spots of architects, designers, and developers/owners. Once they distributed proper number of hats and shirts throughout the plumbing industry, they had completed the circle. How do you circumvent the Engineers? Simple, they are forced to accept it since, we must follow the caravan of the believers. And if there was any doubts, they brochures were modified to address any doubts.
To begin with tank less water heaters, in my perspective are two types, the gas versus electric. I have known the electric as “Insta-hots”. The gas type tank less is merely a kettle where shell and tube fins are immersed into gas burning fire chamber and the water flows through a very small tubing. The water quality as well as the speed of the water through this heat exchanger will convert this product into a major replacement interval. As one puts it, the heat exchanger will be changed like “light bulb” in a light fixture, over and over and over. Tank less water heaters cannot be on recirculation pumps, and if they are their warranty will be reduced substantially. Of course, no one described that the catalogues also indicates the maximum number of hours operations per month to maintain the warranty. In catalogue, their temperature rise now is considered only 70 degrees rise. At 70 degrees, 199,000 btu/hr only provides 5.3 gpm of hot water. If the water temperature is 50 degrees in winter and 70 degrees in summer, you will have 120 degrees water for 5.3 gpm flow. A kitchen sink and shower completes the capability of this product. In commercial kitchen where 140 degrees is required, the gpm reduces to 3.7 gpm, and you will need nearly two of these 199,000 btu/he for three kitchen sinks. story.
The dilemma continues: Is the tank less endless water? If the response is yes, if you are only satisfied with 3.7 gallons of water with 100 degree rise. If not keep adding these 199,000 btu’s/hr at your pleasure. Higher volume is a fallacy, they advertise the 3.7 gpm, yet it is advertised that they produce 4 times the flow. The space savings may be over come with all clearances required in front of the unit, plus if you add the recirculation pump, then a tank is needed. Please note that recirculation pump is always needed for large facilities and long distance runs. The tank is continuously fed with hot water, then it is not on demand. Demand (i.e. the tank) is always seeking the minimum temperature status. If the tank is designed, then there are no advantages for existence of tank less, you own technically a tank type water heater with a segregated independent combustion chamber.
Fortunately, in private conversations with application engineers of the manufacturers, they acknowledge these issues and are not denied. Unlike the Siphonic Roof Drainage vendors, and sales group with large shrouds and large smoke clouds is used as cloaking device, the Tank less Water heater groups are not hiding these scientific issues. Information noted above are available and scattered in different mediums. The selection and liability is carried by the designer/Engineer. Tank less manufacturer’s will continue in their extremely fine advertising campaign with nice brochures, distribute lots of caps and shirts, and subsidizing the logos, advertisements on sides of plumbers’ trucks, and even advertise in various shock jock radio programs during your morning commutes.
On a tangential note, when a dishwasher and a lavatory are combined in a ADA setting, there are several interesting phenomenon. First, the Engineer does not specify the dishwasher. As an appliance, owner or the architects selects the unit. ANSI A117 controls the output temperature of the lav or sink at maximum of 110 degrees F. There are several issues. A boiler plate dishwasher demands 120 degrees input water. A simple tankless is not smart to control the output setting. The output setting is set at maximum of 110, 120, 140, or 150 degrees. As noted earlier, the input city tab water temperature varies as much as 20 degrees. The water heater set at worst case is to be set at say 120 degrees to satisfy the dishwasher only for warmer seasons.
So here is the equation:
Summer time:
Set Water heater at 120 degrees
to satisfy the DW + Pressure/temperature balance valve for sink
Winter time:
Water heater will only provide 100 degrees Temperature
Will the dishwasher be satisfied?
Best Solutions are:
A. Separate water heater for dishwasher set at 140 degrees and a small unit for sinks
B. Output Controlled smarter water heater, to always adjust the incoming water
C. Better Dishwasher, the Swedish dishwashers can give up to 160 degrees internally heated. Most others only heat upto 140 degrees
D. Note that these temperatures have no bearing on hard glue type sticky foods on pans. Pre-rinse is fully required for such issues. Do not rely on temperature to act as scrubber.
E. Temperature only assist in breaking down the adhesion. Depending on age of the cooking surface, type of food, the hills and valleys within the pans will not be effected by ten degrees of temperature.
One last issue before, I conclude, did you know the minimum operating pressures of the insta-hots is near 25 psi. Imagine you design and you do not have proper pressure to activate, now you are in trouble.
Saum
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