

Tankless Electric Water Heater
Point-of-Use Water Heater
Available 3-27 KW Single Phase Voltages
The Hubbell Tankless electric water heater is a highly reliable and easily maintained heater designed for point-of-use or whole house operation. The Hubbell Tankless electric water heater is compact, extremely efficient, takes up minimal space and reduces operating costs. Hubbell's vast experience, meticulous engineering and advanced technology ensure that you can rely on the Hubbell Tankless heater for your water heating needs in even the most demanding applications. The Hubbell Tankless is the right choice for your water heating needs and provides you with an energy efficient, trouble-free and long lasting heater.
- Features
- How It
Works - Product
Specs - Sizing &
Dimensions - Formulas &
Charts - Options
- FAQs
- Downloads
- Technical
Support
Heavy Duty Construction
- Constructed with high grade materials to ensure long operating life
- Simple to install and operate
- Compact space saving design
Reliability
- Engineered to ensure reliable operation
- Wide selection of sizes
High Efficiency
- On demand heating eliminates costly and cumbersome storage tanks
- Instantaneous design reduces stand-by heat loss and significantly lowers operating costs compared to traditional storage tanks
How It Works

The Hubbell tankless electric water heater contains high powered heating elements that heat water only when there is demand for hot water. When hot water is needed, a built in flow sensor measures the exact flow rate and that data combined with temperature readings at the heater's inlet and outlet are processed by the electronic temperature controller. This data is continuously transmitted to the temperature controller, which constantly calculates the precise amount of power (kW) needed to achieve the desired temperature. A zero cross over firing signal is sent to the fast acting triacs in order to module the heating elements to the precise level needed to meet demand. The Hubbell tankless heater uses only as much power as is needed, while delivering accurate and consistent hot water temperature.
Tankless Water Heater Specifications
Residential: 5 Years
Commercial: 5 Years
Residential: 1 Year
Commercial: 1 Year
General Specifications
A sophisticated electronic temperature controller with LED digital display provides the user interface. The temperature controller processes all flow and temperature data and calculates the precise amount of power needed to meet demand.
Operator Control Capabilities | ||
---|---|---|
![]() |
Power Limiting: | Allows the operator to reduce the power consumption by any percentage to provide installation and operational flexibility and savings. |
![]() |
Diagnostics: | Display inlet and outlet temperatures, flow rate and error codes to assist in troubleshooting. |
![]() |
Cost Calculator: | Determine the exact cost of operating the heater. Input your cost per KW·Hr and the controller displays total KW·HRs consumed, total cost of operation, and total hot water usage (shown in gallons or liters). |
![]() |
Temperature Control: | Set the digital display to the desired water temperature in °F or °C. Fully adjustable in 1° increments from 32-194°F (0-90°C). A user adjustable +/- 3° calibration feature provides additional control for superior accuracy. |
Each heating element is switched on/off using a fast acting solid state triac with zero cross over firing control. This switching schema provides full modulation of each heating element, ensuring that the precise amount of heat is added to meet demand. To improve operating efficiency and component longevity, each triac is mounted to a heat sink located on the incoming supply piping so that heat generated by the triac during the switching process is dissipated into the water.
All Hubbell tankless water heaters, including all 3 phase models, are engineered to operate as a balanced load and operate at 0.999 Power Factor. All Hubbell 3 phase models are designed for 3 wire (3 live, 1 ground) and 4 wire power systems and draw equal current across all conductors to maintain the power integrity of the users electrical system. Hubbell does not recommend the use of heaters that operate as an unbalanced load, as is common with staged heaters designed for star systems (3 live, 1 neutral, 1 ground) that require use of the neutral leg. All load switching in Hubbell tankless models is performed as zero cross over, eliminating phase angle firing interference and associated EMI issues.
The Hubbell tankless control schema ensures that usage is equalized across all heating circuits. To achieve this, once the controller has calculated the precise amount of kW required, all circuits are energized in a staggered fashion such that each circuit is proportionally and independently energized and then time staggered between circuits. This Full Resource Staging Schema reduces EMI output, increases component longevity, and provides highly accurate and consistent hot water temperatures. For three phase models, all circuits are fully modulated and synchronized to operate as a balanced load.
Remote Control:Ability to remotely enable or inhibit the heating operation of the unit using one of the following two methods:
1. Customer supplied 24VDC signal is user configured for either Inhibit Mode or Normal Operation Mode.
2. Customer supplied volt free contact is user configured for either Inhibit Mode or Normal Operation Mode.
Priority Control: An integrated SPDT potential free dry contact (NO/NC 10A @ 240VAC) energizes when the unit is heating and de-energizes when not heating. This feature is useful when it is desirable to give the water heater priority over another electrical load to ensure that both are not operational at the same time.
Outline Dimensions and Model Selection
3-18 KW Models (2 Element)

KW Selection Chart | |||
---|---|---|---|
Model Number | KW Ratings | ||
240V | 220V | 208V | |
R003-2S | 3 | 2.5 | 2.2 |
R005-2S | 4.5 | 3.7 | 3.3 |
R007-2S | 7 | 5.8 | 5.2 |
R009-2S | 9 | 7.5 | 6.7 |
R011-2S | 11 | 9.2 | 8.2 |
R014-2S | 14 | 11.7 | 10.5 |
R016-2S | 16 | 13.4 | 12 |
R018-2S | 18 | 15.1 | 13.5 |
21-27 KW Models (3 Element)

KW Selection Chart | |||
---|---|---|---|
Model Number | KW Ratings | ||
240V | 220V | 208V | |
R021-3S | 21 | 17.6 | 15.7 |
R024-3S | 24 | 20.1 | 18 |
R027-3S | 27 | 22.6 | 20.2 |
Heating Capacity and Amperage Chart
Model No. | KW Ratings at Various Voltages | Heating Capability in GPM at °F Temperature Rise (°FΔT) | Max Amps at 100% output | |||||||
---|---|---|---|---|---|---|---|---|---|---|
1 Phase Voltages | ||||||||||
240V | 220V | 208V | 40°F ΔT | 60°F ΔT | 80°F ΔT | 100°F ΔT | 240V | 220V | 208V | |
R003-2S | 3 | 0.51 | 0.34 | 0.26 | 0.20 | 12.5 | ||||
2.52 | 0.43 | 0.29 | 0.21 | 0.17 | 11.4 | |||||
2.25 | 0.38 | 0.26 | 0.19 | 0.19 | 10.8 | |||||
R005-2S | 4.5 | 1.19 | 0.80 | 0.60 | 0.48 | 29 | ||||
3.78 | 0.64 | 0.43 | 0.32 | 0.26 | 17.1 | |||||
3.37 | 0.57 | 0.38 | 0.29 | 0.23 | 16.2 | |||||
R007-2S | 7 | 1.19 | 0.80 | 0.60 | 0.48 | 29 | ||||
5.88 | 1.00 | 0.67 | 0.50 | 0.40 | 26.7 | |||||
5.2 | 0.89 | 0.59 | 0.44 | 0.35 | 25 | |||||
R009-2S | 9 | 1.54 | 1.02 | 0.77 | 0.61 | 37.5 | ||||
7.56 | 1.29 | 0.86 | 0.64 | 0.52 | 34.3 | |||||
6.7 | 1.14 | 0.76 | 0.57 | 0.46 | 32.2 | |||||
R011-2S | 11 | 1.88 | 1.25 | 0.94 | 0.75 | 46 | ||||
9.24 | 1.58 | 1.05 | 0.79 | 0.63 | 42 | |||||
8.2 | 1.40 | 0.93 | 0.70 | 0.56 | 39.4 | |||||
R014-2S | 14 | 2.39 | 1.59 | 1.19 | 0.96 | 58 | ||||
11.76 | 2.01 | 1.34 | 1.00 | 0.80 | 53.4 | |||||
10.5 | 1.79 | 1.19 | 0.90 | 0.72 | 50.4 | |||||
R016-2S | 16 | 2.73 | 1.82 | 1.36 | 1.09 | 67 | ||||
13.44 | 2.29 | 1.53 | 1.15 | 0.92 | 61 | |||||
12 | 2.05 | 1.36 | 1.02 | 0.82 | 57.6 | |||||
R018-2S | 18 | 3.07 | 2.05 | 1.54 | 1.23 | 75 | ||||
15.12 | 2.58 | 1.72 | 1.29 | 1.03 | 68.7 | |||||
13.5 | 2.30 | 1.54 | 1.15 | 0.92 | 64.9 | |||||
R021-3S | 21 | 3.58 | 2.39 | 1.79 | 1.43 | 87.5 | ||||
17.64 | 3.01 | 2.01 | 1.50 | 1.20 | 80.1 | |||||
15.75 | 2.69 | 1.79 | 1.34 | 1.07 | 75.7 | |||||
R024-3S | 24 | 4.09 | 2.73 | 2.05 | 1.64 | 100 | ||||
20.16 | 3.44 | 2.29 | 1.72 | 1.38 | 91.6 | |||||
18 | 3.07 | 2.05 | 1.54 | 1.23 | 86.5 | |||||
R027-3S | 27 | 4.61 | 3.07 | 2.30 | 1.84 | 112 | ||||
22.68 | 3.87 | 2.58 | 1.93 | 1.55 | 103 | |||||
20.25 | 3.45 | 2.30 | 1.73 | 1.38 | 97.3 |
Alternate voltages including 277, 380, 415, 440, 575 and 600 volt available. Please contact us directly for exact KW availability in these voltages.
For 3 phase voltages, please see Hubbell Model TX.
Sizing Formulas
Step 1
KW Requirement:________ GPM x ________ °FΔT x 0.1465 = ________ KW
Temperature Rise:
________ KW x 6.824 ÷ ________ GPM _________ °FΔT
Flow Rate:
________ KW x 6.824 ÷ ________ °FΔT = __________ GPM
Step 2
Choose the Tankless model with the KW rating which meets the peak demand (GPM) and required temperature rise (°FΔT) for your application.Step 3
Choose the supply voltage available. Note the total amperage draw of the unit and verify availability.Voltage De-Rating Factors
Rated Voltage | Applied Voltage | De-Rating Factor |
---|---|---|
240 V | 230 V | 92% |
240 V | 220 V | 84% |
240 V | 208 V | 75% |
(Applied Voltage² ÷ Rated Voltage²) x Rated KW = KW output at applied voltage
Optional Equipment
- Inlet and Outlet Valve assembly simplifies installation and includes unions, shut offs, check valve, drain ports and pressure relief valve
- Air separator to clear the incoming cold water of micro air bubbles, sand, dirt and rust. Recommended for use with well water systems
- Descaler kit simplifies the process of cleaning the heater and removal of mineral deposits
- For heaters suitable for operation with 3 phase voltage, please see Hubbell Model TX
- Special construction features available
- Remote Control Display allows the heater to be installed in a remote location. The 3" x 5" NEMA 4 display enclosure can be located up to 250' from the heater and gives the operator full remote control and monitoring capabilities
- An ASSE 1070 code compliant Thermostatic mixing valve to increase the amount of hot water available. Valve is 1/2" (-UT) size and adjustable from 80-120°F. Typically used when supplying hot water to multiple lavs from a single water heater.
Please note: optional equipment may impact overall dimensions and weight. Please request submittal drawing from factory.
Downloads
Technical Documents
- Tankless Brochure PDF (3.6 MB)
- Tankless AIA Master Spec PDF (106 KB)
- Tankless AIA Master Spec DOC (15.0 KB)
- Tankless O&M Manual PDF (1.3 MB)
- Tankless O&M Manual (Spanish) PDF (1.3 MB)
- Tankless Low Lead Certificate PDF (37.6 KB)
- 3-18 KW Revit File RFA (1.7 MB)
- 21-27 KW Revit File RFA (1.4 MB)
Many of our products literature is available online for download. To open these files, a PDF viewer is required. If you do not have one, Adobe provides Acrobat Reader free of charge for viewing only. Use this link to download Acrobat Reader. You may also choose to download the file to your PC for future reference or printing. On most operating systems, simply right-click on the links below, choose "Save target as..." or "Save link as...", choose a location and it will save the document to your computer for future reference.