If a Rheem RETEX-27 is not heating reliably, start by confirming the exact model and recording any display code, then check whether demand or low fixture flow could explain the symptom. The RETEX-27 is a high-load electric tankless heater, so breaker, wiring and internal-component problems are not casual DIY checks. Use the unit’s rating label and model-specific Rheem documentation to guide next steps; have a licensed electrician or qualified water-heater professional assess suspected electrical faults.
Start with the exact unit and symptom
“Rheem Retex 27” refers here to the Rheem Performance Series RETEX-27 electric tankless water heater. Before using troubleshooting advice, check the appliance rating label for the model and voltage variant. Rheem’s product page links the Use and Care Manual and other model-family documents; use the manual that matches the installed unit rather than assuming a procedure applies across Rheem models. Rheem RETEX-27 product page
- Write down the exact symptom: no hot water, intermittent heating, water going cool during simultaneous use, or a fixture that never triggers heating.
- If the display shows a code, record it exactly. Do not infer its meaning from a code list for a different Rheem product.
- Note which fixtures were running and whether the issue occurs at one fixture or throughout the home.
Rheem RETEX-27 has substantial electrical requirements
Rheem’s specification sheet dated November 2024 lists the RETEX-27 at 27 kW, 240 V and 113 A, with three 40 A double-pole breakers and a recommended 200 A household electrical service panel. These are manufacturer specifications, not confirmation that a particular home’s installation is correct. The appliance label and applicable installation manual govern the specific unit. Rheem also notes that converting from an electric tank to electric tankless often requires a panel upgrade. Rheem electric tankless specification sheet
If breakers repeatedly trip, wiring appears damaged or hot, or you notice a burning smell, stop using the heater. If you can safely reach the relevant breaker without approaching damaged wiring or other hazards, turn it off and call a licensed electrician or Rheem-qualified service professional. Do not remove covers, probe live circuits, change breaker sizes, or replace internal electrical parts as a homeowner troubleshooting step.
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#1 Best Overall
- External digital thermostatic control with LED display (+/1 degree accuracy)
- Most advanced self-modulation, adjust power to meet hot water demand
- Durable Copper immersion three heating elements, field Serviceable
- Simple installation – bottom 3/4 inch NPT water connections
- Threaded for easy replacement, simple installation, digital temperature display
If the RETEX-27 has no hot water or heats intermittently
Check for a household electrical issue safely
Because this is a high-load appliance, an interrupted supply or an installation issue can affect heating. A tripped breaker is a reason to call a qualified electrician, especially if it trips again after being reset or if there are signs of heat or damage. Do not assume a reset will resolve the underlying problem, and do not open the heater to inspect wiring or components.
Compare demand with the model’s published capacity
Tankless output depends on incoming groundwater temperature and how much hot water is being drawn at once. Rheem’s November 2024 sheet gives RETEX-27 flow ratings at a 120°F set point ranging from 2.2 GPM in Zone 1 (37°F/3°C groundwater) to 4.3 GPM in Zone 9 (77°F/28°C groundwater). Rheem advises adding the flow rates of fixtures used simultaneously and comparing the total with the applicable temperature-zone rating. These are manufacturer sizing figures, not a guarantee of output in every installation. Rheem electric tankless specification sheet
Rank #2
- ✅[Easy Installation] The structure of this element is a screw in type, taking just minutes to perform routine maintenance. Package includes heating element, new O-Ring and screw
- ✅[Comapatible] 90240 water heater element replaces 80240 heater element, fits for Ecosmart Electric Tankless Water Heater ECO 18, ECO 24, ECO 27, ECO 36. Also compatible with Eemax HA036240, HA027240, HA018240, HA024240, PR036240, PR027240, PR018240, PR024240, EEM24036, EEM24027, EEM24018, EEM24024, Rheem RTEX-36, RTEX-27, RTEX-18, RETEX-36, RETEX-27, RETEX-18, RTEX-24, RETEX-24, Richmond RMTEX-36, RMTEX-27, RMTEX-18,RMTEX-24, iHeat/Drakken AHS27D, AHS18D, AH27, AH18, AHS24D, AH24
- ✅[Save Money] If your 90240 heating element fails, causing issues such as no heating, excessively long heating times, low water temperature, abnormal water pressure, or slow water flow, we recommend replacing this heating element. Using this product allows you to avoid replacing the entire water heater, saving you significant repair costs
- ✅[High Quality] Our heating element is made of high-quality Purple Copper, and added with an anti-oxidation coating, which has better heat conduction effect, can withstand higher temperatures, corrosion resistance and mineral accumulation resistance. It can minimize failures and extend the service life of the water heater and is an excellent choice for water heaters prone to hard water
- ✅[Reliable After-Sales Service]: We offer comprehensive support for our products. If you encounter any issues related to installation, product defects, or daily use, please contact us directly. Our customer service team is committed to providing you with a prompt solution within 24 hours to ensure your complete satisfaction
For example, Rheem’s sizing illustration assigns 2 GPM to a shower and 1.5 GPM to a kitchen faucet, for a combined 3.5 GPM. That exceeds the sheet’s 2.2 GPM Zone 1 rating, but is below its 4.3 GPM Zone 9 rating. A heater operating within its published capacity can still feel inadequate when multiple fixtures run together, particularly with colder incoming water.
Use the correct manual for any code or reset procedure
Use the RETEX-27 Use and Care Manual linked from Rheem’s product page for model-specific instructions. If the display code is not explained there, contact Rheem support or a qualified service professional with the exact model and code. The accessible general Rheem tankless quick guide is not a substitute for the RETEX-27 manual. Rheem tankless installation guide
Rank #3
- HE90240 Fitment: 90240 Water Heater Element for Ecosmart Eco 27 18 36,for Rheem RTEX-27 RTEX-18 RTEX-36, RETEX-27 RETEX-18 RETEX-36,for Richmond RMTEX-27 RMTEX-18 RMTEX-36 Heating Element
- HE90240 Element Models: 90240 Heating Element fit for iHeat/Drakken AHS27D AHS18D AH27 AH18,for Eemax EEM24027 EEM24018 EEM24036 (blue unit), for Eemax HomeAdvantage HA027240 HA018240 HA036240,for Eemax ProAdvantage PR027240 PR018240 PR036240
- Long-Lasting Quality: The 9000W 240V water heater elements are constructed from copper with antioxidant coating for good strength, excellent thermal conductivity, efficient heat transfer.In order to ensure greater durability and firmness, This heating element does not undergone the pickling process and have longer lifespan
- Screw-in Installation: The heating element is designed with an easy screw-in installation,ensuring a hassle-free installation process for your water heater
- Specification: HE90240 electric water heater element parameter is 9KW 240V and our tankless water heater element adopts screw-in structure,which can be directly replaced
If hot water turns cool when several fixtures run
Total the estimated flow of the fixtures in use and compare it with the published rating for the home’s groundwater-temperature zone. Rheem’s sheet rates the RETEX-27 at 2.2 GPM in Zone 1 and 4.3 GPM in Zone 9 at a 120°F set point; colder incoming water and simultaneous demand reduce the flow available at that target temperature. Check whether the symptom disappears when fewer fixtures draw hot water. If it does not, consult the model-specific manual or arrange professional diagnosis rather than assuming capacity is the only cause. Rheem electric tankless specification sheet
If a low-flow fixture does not trigger heating
Rheem lists the RETEX-27 flow activation rate as 0.3 GPM in its November 2024 specification sheet. Flow below that threshold may not activate heating. Check the affected fixture’s flow and look for fixture-side restrictions, such as a clogged aerator, valve issue or plumbing restriction. If the flow is adequate but the heater still does not respond, consult the manual or a professional; do not bypass safety devices or make internal adjustments. Rheem electric tankless specification sheet
Rank #4
- This refurbished product is tested and certified to look and work like new. The refurbishing process includes functionality testing, basic cleaning, inspection, and repackaging. The product ships with all relevant accessories, and may arrive in a generic box
Do not apply gas-heater error codes to this electric model
Rheem’s general tankless quick guide lists examples such as A011 (failed ignition), A012 (lost flame), T113 (not enough water flow) and A090 (vent blockage). Those descriptions concern gas-heater functions and are not established RETEX-27 electric diagnostics. Do not use them to diagnose this model. The RETEX-27 product page links its Use and Care Manual, but consult that model-specific document for any code shown on your unit. Rheem tankless installation guide · Rheem RETEX-27 product page
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Maintenance and suspected scale
Rheem’s general tankless quick guide recommends cleaning or flushing a tankless heater every year to a year and a half. That interval is general guidance, not proof that scale is causing a particular RETEX-27 symptom. Follow the exact model’s Use and Care Manual or have a qualified service professional determine whether maintenance is needed and perform it using the proper procedure. Compatibility of a third-party flushing kit with the RETEX-27 should be confirmed before use. Rheem tankless installation guide · Rheem RETEX-27 product page
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- Water Heater Flow Sensor: FSA QC MEDLRG flow sensor can help activate tankless electric water heater for ecosmart to heat hot water as it flows through. If the LED display not illuminated while water is running, then you need to replace it with a new water flow sensor for ecosmart.
- Compatibility: Tankless hot water heater flow sensor is compatible with Ecosmart ECO 18 , ECO 24, ECO 27 and ECO 36 models water heater. Flow sensor for ecosmart also compatible with Rheem Retex-27 hot water heater.
- Design Excellence: The circuit board design of flow meter for ecosmart is very precise and ensures that the sensor accurately measures the water flow and activates the water heater to heat the hot water. Not only leak proof, but also works very well.
- High-quality Copper: The wire specification of flow sensor for eco 18 is 24AWG/ 300V (≤80℃), and the wire is made of high quality copper wire for better thermal conductivity, which allows it to work properly even when the water heater is operating at high temperatures.
- Easy to Install: Water heater flow sensor assembly is easy install and wiring was a quick plug. The connect of tankless water heater flow sensor has been precisely measured and can perfectly match the connector on both ends of the tankless water heater for ecosmart.
When to call a professional
- Repeated breaker trips, suspected wiring faults, hot or damaged wiring, or a burning smell: contact a licensed electrician or qualified service professional.
- An unexplained display code, continuing loss of heat, or suspected internal component failure: provide the professional with the rating-label details and exact display message.
- Uncertainty about installation capacity or simultaneous hot-water demand: have a professional compare the installation and household service with Rheem’s specifications.
Rheem’s general guide recommends that tankless products be installed and serviced by a licensed plumber or professional service technician. The product page provides Rheem’s Find a Pro pathway and parts lookup; confirm the diagnosis and exact part number before purchasing replacement parts. Rheem tankless installation guide · Rheem RETEX-27 product page
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