Specifications Sheet

Rheem RTEX-18 Classic 18 kW 4.4 GPM Tankless Electric Water Heater Ind – FactoryPure

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Rheem-RTEX-Series-Spec-Sheet
Water

Residential Electric Professional Classic
Tankless Water Heaters

Rheem® Professional Classic® RTEX Tankless Electric Water Heaters
Provide Endless Hot Water in a Durable, Space-Saving Design
RTEX - 18, RTEX - 24, RTEX - 27, RTEX - 36 tankless electric water heaters are ideal for new construction builds and all applications in the home including pointof-use installation. The durable, compact design allows installation in tight spaces. In warmer climates, these models provide enough hot water to run multiple fixtures simultaneously. All RTEX models include a lifetime limited warranty. To select a unit that meets electrical and hot water gallons per minute (GPM) requirements, please use the sizing guide.
PERFORMANCE FEATURES
· Saves Space ­ up to 93% smaller than a standard electric water heater
· Saves Energy ­ zero standby heat loss when installed near the point-of-use
· M ore Hot Water ­ up to 4 times the hot water delivery of a standard electric tank (per hour)
· H igh Efficiency ­ UEF up to .94 and advanced self-modulating technology only consumes the power needed to satisfy hot water demand
· Copper immersion heating elements fit into a multi-chamber design to improve the thermal performance providing better temperature control and faster recovery of hot water
· Copper heat exchanger transfers heat fast and resists corrosion
· Durable powder-coated shell with a galvanized steel backplate
· Brass NPT fittings located on the bottom for the inlet and outlet water connections provide strength and durability
· Designed to be mounted in an upright position with the inlet and outlet water connections at the bottom of the unit for ease of installation
· Venting is not required to operate, simplifying the installation process compared to a gas tankless water heater
· Digital thermostatic temperature controls in 1-degree increments ranging from 80°F - 140°F (26°C - 60°C)

WHOLE HOME

RTEX - 18

RTEX - 24

RTEX - 27

RTEX - 36

WARRANTY
· Limited Warranty ­ 5 Years - Leaks, 1 Year - Parts
See Use and Care Manual for complete information.

These products meet a stringent set of our company's internally defined sustainability standards.
®

Tested and certified by the Water Quality Association against NSF/ANSI 372 for lead free compliance.

Tankless Electric Specifications and Minimum Requirements

DESCRIPTION

FEATURES

DIMENSIONS (SHOWN IN INCHES)

MODEL NUMBER

POWER (kW)

VOLTAGE

TOTAL UNIT AMPERAGE (AMPS)

RECOM'D BREAKER
SIZE

HOUSEHOLD

UNIFORM REQUIRED

ELECTRICAL

ENERGY WIRE

SERVICE PANEL

FACTOR (75°C

RECOM'D PHASE (UEF) INSULATION)

HEIGHT

WIDTH

DEPTH

WATER CONN.

# OF

SHIP

HEATING WEIGHT HEAT

OPERATING

CHAMBERS (LBS.) EXCHANGER PRESSURE

FLOW ACTIVATION RATE (GPM)

RTEX - 18

18

240

75

2 x 40 A Double Pole

150 AMPS

1

0.94 2 x 8 AWG* 17 14 3.635 3/4" NPT

2

14.78

Copper

Min: 25 PSI Max: 150 PSI

0.3 GPM

RTEX - 24

24

240

100

3 x 40 A Double Pole

200 AMPS

1

0.93 3 x 8 AWG* 17 17 3.625 3/4" NPT

3

17.8

Copper

Min: 25 PSI Max: 150 PSI

0.3 GPM

RTEX - 27

27

240

113

3 x 40 A Double Pole

200 AMPS

1

0.93 3 x 8 AWG* 17 17 3.625 3/4" NPT

3

17.8

Copper

Min: 25 PSI Max: 150 PSI

0.3 GPM

RTEX - 36

36

240

150

4 x 40 A Double Pole

300 AMPS

1

0.94 4 x 8 AWG* 17 21 3.625 3/4" NPT

4

22.7

Copper

Min: 25 PSI Max: 150 PSI

0.3 GPM

NOTE: When converting from an electric tank to an electric tankless water heater, household electric service panel upgrades are often required. Please see the electric service panel recommendations above.
*AWG - American Wire Gauge

IINNTTEEGGRRAATETDE DHOHMOEMCEOCMOFOMRFTO RT

Rheem.com
04/24 FORM NO. TKE-101 Rev. 8

RTEX - 18

RTEX - 24

RTEX - 27

Water

Residential Electric Professional Classic
Tankless Water Heaters

RTEX - 36

13.9"

3.6"

12.9"

17.0"

15.1"

3.6" 17.0"

17.0" 16.0"
15.1"

3.6" 17.0"

17.0" 16.0"
15.1"

3.6" 17.0"

20.8" 19.8"
15.1"

5.9"

5.9"

5.9"

9.8"

SIZING A TANKLESS ELECTRIC WATER HEATER IMPORTANT ­ Verify that your home meets the electrical requirements. See specifications and minimum requirements. (front side)

1 Estimate your total household gallons per minute (GPM) needs by adding up the average flow rates by fixture (showers, faucets, dishwasher, washing machine) that run at the same time.
Ex. 1 shower and 1 kitchen faucet running at the same time adds up to 3.5 GPM (2 + 1.5 = 3.5 GPM)

2 Locate your zone on the map. U.S. Average Ground Water Temperature Zone Map

Average Flow Rates (GPM) by Fixture

Low Flow Faucet

0.5

Bathroom Faucet

1

Kitchen Faucet

1.5

Shower

2

Dishwasher

2

Washing Machine

3

Flow rates may vary.

CAN

AK

HI

PR

Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Zone 6 Zone 7 Zone 8 Zone 9
3 Select the model that can supply you with the estimated total household gallons per minute (Step 1) with the ground water temperature in your zone.

Flow Rate Capacity Table by Zone (Gallons Per Minute - GPM) 37°F 42°F 47°F 52°F 57°F 62°F 67°F 72°F 77°F

Model #

Zone 1 37OF/ 3°C

Zone 2 42OF/ 5°C

Zone 3 47OF/ 8°C

Zone 4 52OF/ 11°C

Zone 5 57OF/ 14°C

Zone 6 62OF/ 17°C

Zone 7 67OF/ 20°C

Zone 8 72OF/ 22°C

Zone 9 77°F/ 28°C

RTEX - 18

1.8

2.0

2.1

2.6

0.9

2.9

3.2

3.7

4.4

RTEX - 24

2.4

2.6

2.8

3.1

3.4

3.8

4.3

5.0

5.9

RTEX - 27

2.7

2.9

3.2

3.5 OPTIONAL ­3F.8low Regulator 4S.i3zing Table by Z4o.n9e (Gallons Per5M.6inute = GPM) 6.6

RTEX - 36

3.6

3.9

4.2

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OPTIONAL ­ Flow Regulator Sizing Table by Zone (Gallons Per Minute ­ GPM) The flow regulator fitting threads onto the outlet water connection and limits the outlet flow to the GPM specified in the table. Select the appropriate GPM insert for your model based on your zone. This is an optional part to ensure accurate temperature output.

Model # RTEX - 18 RTEX - 24 RTEX - 27 RTEX - 36

Connection kW Size Part #
18 ¾" NPT IFR 3-4 24 ¾" NPT IFR 3-4 27 ¾" NPT IFR 3-4 36 ¾" NPT IFR 3-4

Zone 1
37°F/ 3°C
­ 2.0 2.0 3.0

Zone 2/3

Zone 4/5

Zone 6/7

Zone 8/9

42-47°F/ 52-57°F/ 62-67°F/ 72-77°F/

5-8°C 11-14°C 17-20°C 22-28°C

2.0

2.0

2.0

3.0

2.0

3.0

3.0

4.0

2.0

3.0

4.0

5.0

4.0

4.0

5.0

­

NOTE: (­) indicates flow regulator insert is not recommended in this zone. In keeping with its policy of continuous progress and product improvement, Rheem reserves the right to make changes without notice.

Rheem.com | 800.374.8806 Manufacturers National Service Department 400 Captain Neville Drive, Waterbury, CT 06705

IINNTTEEGGRRAATETDE DHOHMOEMCEOCMOFOMRFTO RT

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04/24 FORM NO. TKE-101 Rev. 8


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