There are many reasons to consider specifying a tankless water heater for an initial build or retrofit in a commercial or industrial application but there is one over riding reason: efficiency.
Tankless water heaters operate efficiently because they only draw energy when needed.
Temperature controlled units heat directly to a set-point temperature and expend only the energy needed to reach and maintain it.
By comparison, boilers expend a lot of energy to heat water above usage temperature, continuously serving recirculation loops or boosting storage tanks. Often the hot water must be overheated then cooled through a mixing valve to reach the desired temperature.
Simply put, tankless water heaters are energy efficient. Energy is only drawn when hot water is needed, and then only the energy required to reach the desired temperature is consumed.
Hot Water On Demand
To truly understand why a tankless water heater is so efficient, one must understand how it functions.
When hot water is needed, a flow sensor registers the demand. It activates the temperature controller that takes water temperature readings inside the heat exchanger as the water is flowing through it.
If the temperature of the water is lower than the set-point temperature the heating elements energize.
In all of our models this process happens within 2 seconds or less.
The energized elements begin to rapidly increase the water temperature driving the outlet temperature quickly toward set-point.
Up to this stage, most electric tankless water heaters on the market are nearly identical in function. From this point forward, control theories and design vary greatly and sometimes performance follows suit.
Keltech’s Tankless Advantage to the Nth Degree:
Precise Temperature Control
Keltech’s Acutemp control process works as follows: As the temperature increases from startup, the controller monitors the output temperature and weighs the energy available and requirements against the set-point temperature.
This temperature rise is controlled, and curves to set-point are predicted, evaluated and changed based on speed of temperature increase.
This data is then used to predict time-to-temperature and stabilize the temperature rise through a modulated duty cycle that provides the exact amount of energy required to meet your temperature setting.
Many Keltech Acutemp models can reach set-point and stabilize within +/- 1ºF, and maintain that temperature for the duration of the process.
Continuous Temperature Control Throughout the Heating Process
Once set-point temperature is reached, the controller constantly monitors output temperature against the set-point and can vary amperage to the elements, sometimes as fast as 120 times a second. Other factors are sometimes monitored in control systems to calculate the energy needed. Should the incoming water temperature vary or flow change drastically, the controller must quickly recalculate this energy need and deliver the proper amperage to the heating elements. The speed at which this calculation happens plays a great role in customer satisfaction and output temperature stability.
As flow rate through a tankless water heater increases, so does the duty cycle commanded by the controller. The unit can accommodate this increase in flow until energy demands exceed the capacity of the unit. Once the controller reaches 100% duty cycle at set-point temperature, any further increase in flow will have a corresponding decrease in output temperature. This is why correctly sizing a tankless water heater is critical.
How to Specify or RightSize Your Tankless Water Heater
Correctly sizing a tankless water heater requires three variables common to any project:
• Flow rate
• Temperature rise
• Available local utilities
When calculating the flow rate, all aspects of the project must be considered. A unit dedicated to a single process or fixture simplifies the process greatly.
However, when specing multiple fixtures or processes, total flow becomes slightly more complicated. In these instances, maximum potential flow rates should be dictated by the sum of connected fixtures if simultaneously in use.
Desired temperature rise should not be confused with process or set-point temperature. Temperature rise, commonly referred to as delta “T,” is the difference between incoming water temperature and desired set-point temperature.
This difference can vary greatly due to variance in regional ground water temperature, storage, or the possibility of a “boosted” supply. For sizing purposes, the lowest potential incoming water temperature should be factored.
When calculating necessary set-point temperature, be sure to factor in heat losses within the delivery to the process or fixture if precise temperature is required.
Once these numbers are established, the difference is the maximum delta “T” for your project.
Properly Sizing or Specing Your Tankless Water Heater
1. Flow rate (GPM)
2. Temperature rise ( 
T ºF)
To determine the size and kilowatt rating you need, apply this formula:
The result of this formula is the maximum kW needed to accomplish your project requirements for on-demand heated water. Other media will vary slightly. This formula is a nearly universal method of calculation for energy input to yield temperature at required water flow.
Your kW requirements in conjunction with your local electric utility’s power capacity provide the foundation for sizing and specifying a tankless water heater. Your local utility’s ability to support peak needs must also be taken into consideration. Keltech’s trained sales engineers are ready to work with specifying engineers at any point during this process.
A Quick Note on Utilities:
Keltech manufactures electric tankless water heaters. The following calculations will be based on results yielding a kW requirement. This can be easily converted to Btu/h if sizing for a gas tankless water heater.
Voltage availability should be considered in the final application. Keltech tankless water heaters accommodate the most common service voltages in the world. Our product line voltage range extends from 208V single phase to 600V three phase.
Once flow rate and temperature rise are established, these variables can be added to the sizing formula below to determine the maximum kW output required for the project. Achieving maximum kW can be accomplished with a single unit or by pairing multiple units together. Keltech’s single unit product line ranges from 3kW to 144kW.
The Truth About Tankless: What Can You Believe?
Can Tankless Hot Water Heaters Provide Instantaneous Hot Water?
No. The use of the word “instantaneous” is a misnomer and should be discontinued. A more appropriate phrase is “on-demand.” Tankless water heaters perform on-demand and can deliver hot water within seconds – not instantaneously.
The water still has to be heated within the unit (time-to-temperature) and then there is the distance of plumbing runs. The truth: tankless water heaters perform on-demand and deliver hot water within seconds not instantaneously.
Can Tankless Water Heaters Provide an Unlimited Flow of Hot Water?
Only if the project is specified correctly. With correct sizing, you could have an unlimited and continuous flow of hot water. If realistic consumption requirements are considered and factored into the specification, the end result is a water heating solution with enough capacity to meet the needs of most projects. To properly specify a tankless water heater, please refer to our sizing formula.
What is More Energy Efficient: A Boiler or a Tankless Water Heater?
There is no universal ratings system or standard established or adopted for testing and comparing energy efficiency between boilers and tankless solutions. Many rating systems with sound engineering calculations and solid test criteria currently exist. Unfortunately, measurable attributes vary, as do conclusions. In our opinion, the inherent advantage of on-demand water heating in a direct-heat electric configuration makes a compelling argument. Power on. Power off.
Is There a Tankless Disadvantage When it Comes to Applications?
Tankless systems may yield less than desirable results where pulsed flow process cycles are fed directly from the unit in 3-15 second intervals and precise temperature delivery is required. Pulsed flow cycles are common in sporadic spray wash processes.
The quick timing intervals do not permit the control to raise and fully stabilize the water temperature before the cycle terminates. Subsequent activations may allow the control to erroneously factor latent heat from the heating elements into its next duty cycle. The probability of variable temperature output would likely be less than desirable in this type of application.
Is There a Workaround for a Sporadic Spray Wash Process?
Yes. While not impossible to meet this need utilizing today’s technology and direct plumbing from a tankless unit (the process would need to be carefully evaluated and control programming specific to its application would be required), a more reasonable solution would be to install a recirculation loop with an appropriately sized tankless unit, or provide the process with another (secondary) source of hot water.
The Keltech Tankless Advantage:
Energy Efficiency.
Precise Temperature Control.
The advantages of heating water on-demand with a Keltech tankless solution are clear. Energy is only consumed when demand necessitates it. The amount of energy expended is equal to the requirement of the need. The energy is released, timed to requirement, and waste is minimized as the water is consumed immediately after the expenditure.
The next time your engineering firm specifies a water or fluid heating process, consider a Keltech tankless solution.
About Keltech Tankless Water Heaters
Keltech, Inc. engineers and manufactures tankless water heaters that perform on demand.
Custom built to meet temperature and flow rate specifications, Keltech process heaters provide continuous hot water with precise temperature control for commercial and industrial applications.
Keltech also produces sporadic water heating solutions for safety shower and emergency eyewash applications, hot water delivery systems for the aircraft market, and other commercial applications.
Keltech manufactures water heating solutions for the following applications: de-ionized water, reverse osmosis processing, corrosive fluid heating protection, and non-flammable fluid heating.
Tankless Applications
Tankless water heaters seamlessly integrate into many diverse applications and provide reliable, efficient service. Continuous duty heating applications yield great efficiency, especially in direct-heat electric configurations.
Examples of tankless water heating solutions for continuous duty or process heating applications:
• Parts washing
• De-ionized (pure) water heating
• Consumables requiring FDA approval
• Heating corrosive or caustic non-flammable liquids
• Reverse osmosis (R/O) heating applications requiring precise temperature
• Rinsing printed circuit boards
Examples of Sporadic Applications
The measure of tankless energy efficiency increases greatly in applications that require sporadic use. Power on. Power off. Down time has no utility cost. Providing ANSI compliant tepid water for a safety shower application is one example of a sporadic process where on-demand heating can save a great deal on utilities. Aside from the possibility of a chemical injury incident and ANSI mandated testing, tankless safety shower heater utility costs are minimized.
The tankless advantage with sporadic heating applications is clear. Power on. Power off. Continuously heating water, storing heated water and the associated costs of standby heat losses are not necessary when tankless water heaters are specified. Boiler fed recirculation loops to mixing valves are not necessary to install or maintain.
Examples of other tankless water heating solutions for sporadic applications:
• Booster heaters to sterilize medical equipment
• Point-of-use heaters for commercial dishwashers
• Utility closets or janitorial closets
• Scientific, chemistry, pharmaceutical laboratories
• Chemical heating jackets
• Fluid heating solutions
• Radiant heating systems
