Bradford White Water Heater High-Limit Switch (ECO) Replacement — What This Part Does
The high-limit switch (ECO) is built into the upper thermostat on Bradford White electric water heaters and acts as a safety cutoff when tank temperature climbs too high. When water at the top of the tank exceeds safe limits (around 207°F in some models), the ECO opens and cuts all power to the heating elements, putting the heater into a hard lockout until you press the red reset button. The ECO can trip because of an actual overheat caused by a failed thermostat, a shorted element, or loose wiring that allows runaway heating. It can also trip falsely if the thermostat loses full contact with the tank wall or if internal contacts inside the ECO itself degrade over time.
Bradford White’s service documentation calls out checking the high-limit condition first when there is no hot water, then testing for voltage across the high-limit terminals and resetting the ECO once the tank cools to 120°F or below. If the ECO trips repeatedly or will not reset, the upper thermostat assembly must be replaced along with any heating element or wiring found to be shorted, open, or corroded during testing.
Signs It Needs Replacing
- No hot water and the red reset button on the upper thermostat has popped The ECO has opened and locked out all heating until you press the reset button.
- Reset button clicks but the heater still does not heat The high-limit switch or thermostat contacts have failed and will not close even after reset.
- Water temperature climbs much hotter than the dial setting before the ECO trips The thermostat is no longer controlling properly and allows overheating until the safety limit intervenes.
- ECO trips repeatedly within hours or days of each reset A shorted element, loose wire, or defective thermostat is causing real or false overheat conditions.
- Burn marks, melted insulation, or corrosion visible on upper thermostat terminals Heat damage from loose connections or high resistance can cause the ECO to trip or fail outright.
- Only lukewarm water available and the reset button will not stay in The ECO mechanism inside the upper thermostat has worn out and cannot latch closed.
How to Replace It
- Turn off the circuit breaker or disconnect switch feeding the water heater and verify power is off with a non-contact tester at the heater’s junction box.
- Turn off the cold-water supply valve at the top of the tank.
- Remove the upper and lower access panels and fold back or remove the insulation to expose both thermostats and elements.
- Take a clear photo of all wire connections on the upper thermostat for reference, then disconnect every wire from the upper thermostat terminals (including line, load, and element wires).
- Test the heating elements for continuity and for short-to-ground by checking from each element terminal to the tank wall or ground screw (infinite resistance is correct).
- Inspect all wiring, terminals, and wire nuts for heat damage, corrosion, or looseness and repair or replace any damaged conductors.
- Remove the thermostat hold-down bracket or retaining clip, lift out the old upper thermostat, and make sure the thermostat well (or contact pad area) on the tank is clean and flat.
- Install the new upper thermostat firmly against the tank surface, reinstall the hold-down bracket, and reconnect all wires exactly as photographed (line in, load out, element, ground, and any jumper to the lower thermostat).
- Set both thermostats to the same temperature (typically 120°F), replace insulation and access covers, restore water and power, and press the red reset button firmly on the new upper thermostat to close the ECO and allow heating.
The Part You Need
| Part | Notes |
|---|---|
| Bradford White upper thermostat with high-limit (ECO) switch | Amazon | Find your model and serial number on the data plate (usually on the front or side of the tank near the top) and order the exact thermostat by model or cross-reference the element wattage and voltage. |
When to Call a Pro
Call a licensed electrician or water-heater technician if you are uncomfortable working inside an energized appliance, if you find evidence of arcing or melted wires, if the heating elements test shorted to ground, or if the ECO continues to trip after you replace the upper thermostat and verify all wiring is tight and correct. A professional can perform voltage and current draw tests under load and check for grounding faults that a basic multimeter cannot reliably detect. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.