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Error code reference

Aprilaire Hvac Error Code E2

High Refrigeration Pressure

Aprilaire codesAprilaire hvac codes

High Refrigeration Pressure: The temperature of the discharge line exceeds 190°F. Self-correcting unless it occurs for five consecutive compressor starts, usually caused by inlet air temperature too high (>100°F) or very low airflow through the dehumidifier.

First step from the service manual

Turn the ON/OFF toggle switch OFF to reset the diagnostic code, then check if the fan is working and inspect ductwork connections.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What E2 means on a Aprilaire hvac

The E2 error code on an Aprilaire dehumidifier indicates a high refrigeration pressure condition, specifically triggered when the discharge line temperature exceeds 190 degrees Fahrenheit. The discharge line carries hot refrigerant vapor from the compressor to the condenser, and elevated temperatures at this point signal that the refrigerant circuit is operating under excessive stress. The control board monitors this temperature continuously, and when the 190 degree threshold is crossed, it flags the E2 condition to protect the compressor from damage caused by over-pressurization.

This fault is designed to be self-correcting under normal circumstances. If the condition resolves and does not repeat, the system will resume normal operation after a reset. However, if E2 occurs across five consecutive compressor start cycles, the unit will lock out and require intervention. The two most common root causes are inlet air temperatures exceeding 100 degrees Fahrenheit and severely restricted airflow through the dehumidifier. Both conditions reduce the system's ability to reject heat properly, driving discharge line temperatures above the safe operating threshold.

Airflow restriction is typically the more actionable of the two causes. Blocked filters, disconnected ductwork, collapsed flex duct, or obstructions at the inlet or outlet can all starve the unit of the airflow volume it needs to operate within refrigerant pressure limits. Elevated ambient temperatures above 100 degrees Fahrenheit push the refrigerant system beyond its designed operating envelope, and in those cases, addressing the installation environment rather than the unit itself is the appropriate corrective path.

Source: manufacturer service documentation.

Common causes of E2

  1. 01

    Restricted or blocked airflow

    Wiring / connection

    Clogged filters, kinked or disconnected ductwork, or blocked inlet and outlet vents reduce airflow below the minimum needed for safe refrigerant operation. Inspect all ductwork connections and check that the fan is spinning freely and at normal speed.

  2. 02

    Inlet air temperature above 100 degrees Fahrenheit

    Wiring / connection

    The unit is designed to operate within a specific ambient temperature range, and inlet air exceeding 100 degrees Fahrenheit pushes the refrigerant circuit beyond its safe pressure limits. Verify the installation environment and check whether the space is receiving excessive heat from an external source.

  3. 03

    Fan motor failure or reduced fan speed

    Part replacement

    If the fan motor is failing, running slow, or not operating at all, airflow through the coils will be insufficient to remove heat from the refrigerant. Listen for abnormal motor sounds and confirm the fan blade is spinning when the unit runs.

  4. 04

    Collapsed or undersized duct connections

    Wiring / connection

    Flex duct that has collapsed, kinked, or been improperly sized creates high resistance to airflow even when the fan is functioning correctly. Physically inspect all duct runs connected to the unit for proper diameter, shape, and secure attachment.

  5. 05

    Low refrigerant charge

    Part replacement

    A refrigerant leak can cause abnormal pressure and temperature conditions in the discharge line even when airflow is adequate. This cause requires a certified technician to evaluate refrigerant pressures and inspect for leaks.

See the test procedure for each cause

Frequently asked questions about E2

What does E2 mean on a Aprilaire hvac?
The E2 code indicates that the discharge line temperature in the refrigerant circuit has exceeded 190 degrees Fahrenheit, which is the high refrigeration pressure threshold. This typically means the unit is not receiving adequate airflow or the incoming air temperature is above 100 degrees Fahrenheit. The system is designed to self-correct if the issue resolves, but it will lock out after five consecutive compressor starts with the fault present.
Will resetting the unit clear the E2 code on my Aprilaire dehumidifier?
Turning the ON/OFF toggle switch to the OFF position will reset the E2 diagnostic code and allow the unit to attempt normal operation again. However, if the underlying cause such as blocked airflow or excessive inlet air temperature is not corrected, the code will return. If E2 occurs five times in a row during consecutive compressor starts, the unit will require a reset and the root cause must be addressed before it will run reliably.
How do I fix an E2 error on my Aprilaire dehumidifier?
Start by turning the ON/OFF toggle switch OFF to reset the code, then check that the fan is operating and inspect all ductwork connections for blockages, disconnections, or collapsed sections. Confirm that the air entering the unit is not exceeding 100 degrees Fahrenheit. If airflow and ambient temperature are both within acceptable limits and the code returns, a technician should evaluate the fan motor and refrigerant charge.
Is it safe to keep running my Aprilaire dehumidifier when E2 is showing?
The E2 fault is a protective code designed to prevent compressor damage from high discharge line temperatures. The unit has built-in protection that will lock it out after five consecutive compressor starts with the fault present, so continued operation without addressing the cause risks damaging the compressor. It is best to reset the unit, identify and fix the root cause, and confirm the code does not return before resuming normal use.
How much does it cost to repair an E2 error on an Aprilaire dehumidifier?
Repair costs vary widely depending on the cause. If the issue is simply a disconnected duct or a dirty filter, the fix may cost nothing beyond the time to inspect and correct it. A failed fan motor replacement typically runs in the range of 150 to 400 dollars including parts and labor. If the refrigerant circuit requires service such as leak repair and recharge, costs can range from 200 to 600 dollars or more depending on the technician and the extent of the issue.

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