Rheem RETEX-18 Retex Tankless Electric Water Heaters Instructions

: June 1, 2024
: Rheem

Table of Contents

Introduction
Other Models
PERFORMANCE FEATURES
PERFORMANCE
Dimension
SIZING A TANKLESS ELECTRIC WATER HEATER
Flow Rate Capacity Table by Zone (Gallons Per Minute – GPM)
References
Read User Manual Online (PDF format)
Download This Manual (PDF format)

Rheem RETEX-18 Retex Tankless Electric Water

Introduction

Provide Endless Hot Water in a Durable, Space-Saving Design

RETEX – 18, RETEX – 24, RETEX – 27, RETEX – 36 tankless electric water heaters are ideal for new construction builds and all applications in the home including point of-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 RETEX 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.

Other Models

RETEX – 18
RETEX – 24
RETEX – 27
RETEX – 36

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
More Hot Water – up to 4 times the hot water delivery of a standard electric tank (per hour)
High 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)

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.

PERFORMANCE

Tankless Electric Specifications and Minimum Requirements

PERFORMANCE ® T ankless Electric Specifications and Minimum Requirements

INSULATION)

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
RETEX – 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
RETEX – 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
RETEX – 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

PERFORMANCE Tankless Electric Water Heaters

Dimension

RETEX – 18
RETEX – 24
RETEX – 27
**RETEX – 36

**

SIZING A TANKLESS ELECTRIC WATER HEATER

IMPORTANT – Verify that your home meets the electrical requirements. See specifications and minimum requirements. (front side)

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

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
---|---|---|---|---|---|---|---|---|---
RETEX – 18| 1.8| 2.0| 2.1| 2.6| 0.9| 2.9| 3.2| 3.7| 4.4
RETEX – 24| 2.4| 2.6| 2.8| 3.1| 3.4| 3.8| 4.3| 5.0| 5.9
RETEX – 27| 2.7| 2.9| 3.2| 3.5| 3.8| 4.3| 4.9| 5.6| 6.6
RETEX – 36| 3.6| 3.9| 4.2| 4.6| 5.1| 5.7| 6.5| 7.5| 8.8

Flow rates are calculated to a set point of 105°F. Ground water temperature varies seasonally.

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.

Connection| Zone
1
37°F/ 3°C| Zone
2/3
42-47°F/ 5-8°C| Zone
4/5
52-57°F/ 11 14°C| Zone
6/7
62-67°F/
17-20°C| Zone
8/972-77°F/ 22-28°C
---|---|---|---|---|---
Model #| kW| Size| Part #
RETEX – 18| 18| ¾” NPT| IFR 3-4| –| 2.0| 2.0| 2.0| 3.0
RETEX – 24| 24| ¾” NPT| IFR 3-4| 2.0| 2.0| 3.0| 3.0| 4.0
RETEX – 27| 27| ¾” NPT| IFR 3-4| 2.0| 2.0| 3.0| 4.0| 5.0
RETEX – 36| 36| ¾” NPT| IFR 3-4| 3.0| 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