Marey Water Heater Error Codes: ECO150 E1 and E3

By Ray Bennett · Updated 23 October 2026 · 6 min read · Checked against the maker’s manual

Marey Water Heater Error Codes: ECO150 E1 and E3

Short answer

Marey's ECO150 manual identifies E1 as outlet-water temperature above 140 F, or 60 C, and E3 as a temperature-sensor malfunction. Its diagnostic chart reserves both code corrections for a qualified electrician. Turn off the breaker before any reset or service; a cleared display alone does not establish a repair.

Marey water heater error codes need the exact model. In the ECO150 instructional manual, Marey describes E1 as overtemperature protection when outgoing water exceeds 140 F, or 60 C. It identifies E3 as a temperature-sensor malfunction that stops heating.

Those meanings do not apply automatically to Marey gas heaters or other ECO models. This page follows the 16-page ECO150 manual and keeps its qualified-electrician limit for both codes attached to the suggested corrections.

The useful owner checks are recording the display, identifying the model and describing water flow. A reset or internal repair is a separate job. If yours is another model, use our tankless code index to start the right lookup.

Before you start

What to carry: a torch, a phone and the matching manual. Read an accessible outside label or installation paperwork. Photograph the full display, including the temperature unit, and note whether the problem occurs at one fixture or throughout the home.

Gas or electric? The ECO150 covered here is an electric tankless water heater. Its manual requires a fixed circuit-breaker connection. Do not apply gas-heater ignition advice to this model or assume that its front power button isolates the electrical supply.

Renting? Send maintenance the model, code and whether water became unexpectedly hot. Include any known recent plumbing, power interruption or previous reset attempt.

Breaker off before a reset; code corrections belong to a qualified electrician.
Marey’s safety page says to turn off the breaker before resetting this heater. It also prohibits installation, repair or disassembly before shutting power off directly at the circuit-breaker box. Its warning says to disconnect all power supplies before servicing.

Leave the cover fitted. Do not press an internal reset, test live terminals, disconnect a sensor or bridge a safety device. Marey’s diagnostic chart specifically reserves its E1 and E3 corrections for a qualified electrician.

The ECO150 manual warns that a paused heater may initially produce a short burst of very hot water when use resumes. Keep people clear of unexpectedly hot water. Do not use a running shower as a way to test whether an overheating fault has cleared.

Marey warns that frozen water can damage the heat exchanger or lines and cause flooding. Do not switch the heater on if you think it might be frozen. Wait until you are sure it has completely thawed. If there is leakage or suspected freeze damage, stop using the unit and arrange qualified help. Do not open the heater or undertake draining and reconnection from this code guide.

E1: outlet temperature exceeded the protection threshold

Check 1Recording an overtemperature event for qualified diagnosis

Keep the threshold separate from a normal setting

Marey’s product description says the heater cuts electrical heating when the outgoing water exceeds 140 F, or 60 C, and displays E1. It says operation resumes automatically when temperature falls to the set temperature.

Automatic recovery is the protection’s behavior, not proof that the cause has been repaired. Record whether the message returns and whether hot-water flow had become weak. Leave repeated overtemperature events with the installer or electrician for diagnosis.

In its E1 diagnostic row, Marey lists reducing the temperature and increasing water flow as corrective actions. The footnote immediately below the chart says this row and the E3 row should only be performed by a qualified electrician.

Keep that footnote with the advice. Do not open a partly closed internal valve, change wiring or repeatedly operate the heater at different settings to defeat the warning. Ask the qualified person to assess the temperature and flow conditions safely.

Marey's ECO150 manual distinguishes E1 overtemperature from E3 temperature-sensor malfunction. The diagnostic chart reserves both code corrections for a qualified electrician.

E3: a sensor fault needs diagnosis, not a guessed part

Check 2Qualified sensor and circuit diagnosis

Report the sensor message without opening the cabinet

Marey’s ECO150 description says a temperature-sensor malfunction stops the heater and displays E3. Its diagnostic chart directs the reader to the local dealer for that code, under the same qualified-electrician footnote.

The E3 description does not identify a particular inlet or outlet sensor for an owner to replace. Give the technician the actual model and display rather than ordering a part from a different Marey manual.

Keep a note of any recent installation work or water-flow change. Do not unplug a sensor to test the message, swap its wires or bypass it. The manual’s repair instruction remains to use a technician, with the supply shut off before work.

No display and weak water flow are separate observations

Check 3Outside observations that help separate the manual's possibilities

Describe the symptom before calling it an error code

Marey’s operating instructions say the ECO150 can show no further display while in standby. They also describe the display light going off after the heater stops, with a screen touch waking it. A dark screen alone does not prove a failed board.

Its diagnostic chart separately lists disconnected power, a damaged display or a disconnected display-to-board connection for an LED with no signal. Those are possible causes. Leave supply tests and internal connections to the electrician.

For gradually reducing outlet flow, Marey’s chart names a clogged inlet strainer or shower. Its maintenance section also mentions scale or dirt at a faucet aerator or shower head. Report where flow is weak rather than assuming the heater itself is the only restriction.

The manual requires power off for maintenance and water flow off before inlet-screen work. Leave heater-side disassembly to a technician here. Cleaning or changing a fixture does not establish that an E1 or E3 fault has been resolved.

Do not turn a reset into the repair

Check 4A documented fault instead of repeated internal resets

Keep the code and breaker warning in the service request

The ECO150 manual’s reset warning requires the breaker to be off first. It does not give a timed owner restart sequence in its E1 or E3 rows. Do not invent a waiting period or borrow one from another tankless brand.

Its normal operating instructions cover powering an installed heater and establishing continuous water flow with air purged from the pipes. Those installation and startup conditions are not an instruction to energize a heater that has been opened or drained during a code investigation.

Keep it out of use until the qualified person has addressed an unresolved fault and completed the appropriate return-to-service procedure. Record the code and any previous attempts so the next person knows what changed.

For ECO150, Marey puts breaker isolation before reset or service and assigns the code corrections to a qualified electrician. Keep the cover fitted and record the display for that visit.

What each one takes

Finding	Work involved
E1	Qualified temperature and water-flow diagnosis
E3	Qualified sensor and circuit assessment
Dark display	Separate standby behavior from supply or display faults
Weak flow	Locate the restriction before heater-side maintenance
Any reset or service	Breaker isolation first, with all supplies disconnected for servicing

Questions people ask

Where is the Marey ECO150 error code manual?

The manufacturer-authored ECO150 manual saved by Home Depot gives the protection descriptions on printed page 7 and diagnostic chart on page 15.

Does E1 mean I should replace the thermostat?

Marey’s ECO150 description identifies an overtemperature event. It does not select a replacement thermostat from the code alone.

Does E3 identify the outlet sensor?

The ECO150 wording used here says temperature-sensor malfunction. It does not specify an owner replacement of the inlet or outlet sensor.

Can I reset it with the breaker still on?

No. Marey explicitly requires the breaker off before resetting this heater. Internal access and repairs stay with qualified personnel.

Does this cover Marey gas heater codes?

No. This article follows one ECO150 electric manual. Gas models and other ECO variants need their own instructions.

For another electric tankless unit, see the Eemax code guide; for broader symptoms, use tankless water heater troubleshooting with your own model’s manual.

Sources: Marey ECO150 Electric Tankless Water Heater Instructional Manual, 16-page manufacturer PDF saved from Home Depot, printed pages 1, 5 to 7, 14 and 15. Original code chart and overtemperature description visually checked; no other Marey model's code definitions substituted.