Rheem XE40M06ST45U1 Water Heater Problems & Error Codes — Overview
The Rheem XE40M06ST45U1 is a 40-gallon electric storage water heater with dual 4500-watt heating elements. Unlike gas or tankless Rheem models, this unit does not display numeric error codes. Problems show up as no hot water, slow recovery, or a tripped breaker. The most common failures are a tripped ECO high-limit switch, burned-out heating elements, and failed thermostats. Loose or corroded element terminals and control board faults also occur on units with electronic monitoring.
Most Common Problems on This Model
- No hot water and ECO reset button popped The high-limit safety has tripped due to overheating, often caused by a failed thermostat or sediment buildup around the lower element.
- Weak hot water or slow recovery The lower heating element has failed open or the lower thermostat is not closing its contacts, so only the upper element heats the tank.
- No hot water at all The upper heating element has burned out or the upper thermostat has failed, cutting power to both elements in sequence.
- Breaker trips when heater powers on A heating element has shorted to the tank shell or element terminal wiring has failed and is grounding out.
- Intermittent hot water or temperature swings A thermostat is cycling erratically or the thermistor and temperature-sensing circuit has drifted out of calibration.
- Control board shows fault or relay clicks but no heat The electronic control module or relay has failed and is not energizing the element circuit even though the thermostats call for heat.
- Element fails shortly after replacement The tank was not fully refilled and purged of air before power was restored, causing the new element to dry-fire and burn out.
- Burned or discolored element terminals Loose terminal screws or corrosion at the element connections create high resistance, overheat the wiring, and can damage the element or thermostat.
Parts That Commonly Fail
| Part | Notes |
|---|---|
| Upper heating element | Amazon | 4500 W screw-in element that heats first in sequence and commonly fails from scale or dry-fire. |
| Lower heating element | Amazon | 4500 W element at the bottom of the tank where sediment accumulates and causes overheating and burnout. |
| Upper thermostat with ECO | Amazon | Controls the upper element and houses the high-limit safety cutoff that trips on overtemperature. |
| Lower thermostat | Amazon | Switches power to the lower element after the upper zone satisfies and commonly fails from heat cycling. |
Water-Heater Error Codes for This Model
These codes apply to this model line:
When to Call a Pro
Call a licensed electrician or plumber if you are not comfortable working with 240-volt circuits, if the breaker trips repeatedly after resetting, or if you smell burning plastic near the heater. Professional diagnosis is also needed when the ECO trips immediately after reset, when a new element fails within days, or when you find evidence of a leak or water damage around the tank. If the unit has electronic controls and shows a fault you cannot clear, or if voltage testing at the element terminals does not match expected readings, have a qualified technician troubleshoot the control board and wiring. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.