A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater E4 Error Fix: High Limit (ECO) Tripped

The Energy Cut Off (ECO) high-limit safety switch has tripped. Water temperature exceeded the safe maximum (typically 170°F). This protects against scalding and tank damage. Common causes include a malfunctioning thermostat not shutting off elements at set temperature, sediment buildup on elements causing localized overheating, or a shorted heating element. Disconnect power, press the red reset button on the upper thermostat. If it trips again, test both heating elements for shorts to ground and both thermostats for proper operation.

High severity2 fixes available✨ Free fix available

Quick Answer

Error E4 on the A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater means: High Limit (ECO) Tripped. The top-ranked community fix is “Test and Replace Faulty Heating Elements or Thermostats” (hard difficulty, ~90 min, DIY cost: $10-$30). 2 community-ranked fixes available below.

Published February 2026 · 2 fixes · water heater

Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.

When to Call a Professional

While many water heater repairs can be done safely at home, consider hiring a qualified technician if:

This is a high severity error — continued use may cause damage or a safety hazard
The repair involves electrical wiring, gas lines, or refrigerant
You've tried the top-ranked fix and the error persists
You smell gas, see sparking, or notice water leaking
The repair requires specialized tools you don't have
Your appliance is still under manufacturer warranty

Average professional repair cost for this issue: $150-$250.

Other A.O. Smith Models with Error E4

ENS-50 ProMax Electric 50 Gal 4500W ProMax Electric Water Heater with Self-Cleaning

water_heater · 2 fixes

Other A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater Error Codes

Upper Temperature Sensor Failure

2 fixes

Lower Temperature Sensor Failure

2 fixes

Dry Fire Protection Activated

2 fixes

Heating Element Failure

2 fixes

People Also Ask About A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater Error E4

What does error code E4 mean on a A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater?

Error code E4 on the A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater means: High Limit (ECO) Tripped. The Energy Cut Off (ECO) high-limit safety switch has tripped. Water temperature exceeded the safe maximum (typically 170°F). This protects against scalding and tank damage. Common causes include a malfunctioning thermostat not shutting off elements at set temperature, sediment buildup on elements causing localized overheating, or a shorted heating element. Disconnect power, press the red reset button on the upper thermostat. If it trips again, test both heating elements for shorts to ground and both thermostats for proper operation.

How do I fix error code E4 on my A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater?

The most successful fix is "Test and Replace Faulty Heating Elements or Thermostats" (hard difficulty, ~90 minutes). Estimated DIY cost: $10-$30. HomeMD has 2 community-ranked fixes for this error.

Is error code E4 on a A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater serious?

This error is rated high severity. You should address it promptly — continued use could cause damage or safety concerns.

Can I fix A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater error E4 myself?

Yes — the top-ranked community fix ("Test and Replace Faulty Heating Elements or Thermostats") is rated hard difficulty and takes about 90 minutes. Tools needed: T20 Torx screwdriver, Multimeter, Adjustable wrench.

How much does it cost to repair A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater error E4?

DIY cost: $10-$30. Professional repair typically costs $150-$250. Many homeowners save money by trying the top-ranked community fix first.

What other error codes does the A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater have?

The A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater has 4 other known error codes, including: E1 (Upper Temperature Sensor Failure), E2 (Lower Temperature Sensor Failure), E3 (Dry Fire Protection Activated), E5 (Heating Element Failure).

Which other A.O. Smith models have the E4 error?

Error code E4 also appears on 1 other A.O. Smith model: ENS-50 ProMax Electric 50 Gal 4500W ProMax Electric Water Heater with Self-Cleaning. The fix may vary by model, so check each model's specific page for tailored repair steps.

What other error codes does the A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater have?

The A.O. Smith EJCT-50 Elec Lowboy 50 Gal 4500W Lowboy Electric Water Heater has 4 other known error codes:

E1 — Upper Temperature Sensor Failure (2 fixes)
E2 — Lower Temperature Sensor Failure (2 fixes)
E3 — Dry Fire Protection Activated (2 fixes)
E5 — Heating Element Failure (2 fixes)

Which other A.O. Smith models have the E4 error?

Error code E4 also appears on 1 other A.O. Smith model:

ENS-50 ProMax Electric 50 Gal 4500W ProMax Electric Water Heater with Self-Cleaning (water heater) · 2 fixes

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