Nest Thermostat Error E298 — Fix Guide

What Does This Error Mean?

Nest error E298 is a safety shutoff error. The Nest detected that your heating system is running but no heat is actually being produced. This can mean a furnace fault, a fuel supply problem, or a safety lockout in the heating equipment.

Affected Models

Nest Learning Thermostat (all generations)
Nest Thermostat E
Nest Thermostat (2020)

Common Causes

The furnace has a safety lockout due to a fault like a dirty flame sensor or a blocked flue
There is no fuel reaching the furnace (gas supply is off, propane tank is empty)
The furnace filter is severely clogged, causing the furnace to overheat and shut off
A furnace door or access panel is open, triggering a safety switch
The Nest's internal temperature sensor detected no rise in temperature after calling for heat

How to Fix It

Check that your furnace has power. Look for a power switch near the furnace (looks like a light switch) and make sure it is ON. Also check the circuit breaker for the furnace.

A tripped breaker or accidentally flipped furnace switch is a surprisingly common and easy fix.
Check the furnace filter. A completely clogged filter restricts airflow so severely that the furnace overheats and shuts itself off as a safety measure.

Pull out the filter and inspect it. If it is gray and clogged with dust, replace it immediately. Filters should be replaced every 1–3 months.
Check that all furnace access panels and doors are fully closed and latched. Furnaces have a safety switch that prevents operation when the cover is open.

Even a slightly ajar furnace door will prevent the furnace from lighting. Make sure all panels are firmly clicked into place.
Check your gas supply. Make sure the gas shutoff valve near the furnace is in the open position (handle parallel to the pipe = open). If you have propane, check the tank gauge.

If the gas was recently shut off for service or due to non-payment and was not properly restored, the furnace will not light.
Try resetting the furnace. Press the reset button on your furnace (usually a red button on or near the burner assembly). Only press it once — pressing it multiple times can flood the furnace with unburnt gas.

If the furnace resets and lights but E298 returns within a few minutes, there is an ongoing fault that requires a technician.

When to Call a Professional

E298 is a serious safety warning. If your home has no heat and you smell gas, leave immediately and call your gas company. For non-gas issues (oil heat, electric heat), call a licensed HVAC technician. Do not attempt to bypass furnace safety lockouts — they exist to prevent fires and carbon monoxide exposure.

Frequently Asked Questions

Is E298 dangerous? Should I leave my home?

If you smell gas or see flame where there should not be one, leave immediately and call 911 and your gas company. If there is no smell of gas, the situation is not immediately dangerous. However, E298 means your heat is off, which is a serious concern in cold weather. Call an HVAC technician promptly.

What is a furnace safety lockout?

Modern furnaces have multiple safety devices — temperature sensors, pressure switches, flame sensors, and more. If any of these detect an unsafe condition, the furnace goes into 'lockout' mode and stops firing. This prevents dangerous situations like gas buildup or overheating. A furnace lockout needs to be diagnosed and cleared by a technician.

How does Nest know heat is not being produced?

Nest has a temperature sensor inside it. When it calls for heat (turns on the furnace), it monitors whether the temperature actually rises within a certain time period. If no rise is detected, Nest concludes the heating system is not working and displays E298. This is a smart safety feature that basic thermostats do not have.