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HVAC Updated August 14, 2025

Em heat

'Em heat' keeps your hands warm in cold weather, like cozy portable heaters. It uses tiny heat packs that warm up when you open them.

Category

HVAC

Use Case

Provides emergency heating when the primary heating system fails

Variants

Gas, Electric, Hydronic

Key Features

In Simple Terms

What it is

"EM heat" stands for "emergency heat," and it’s a backup heating system in some home heating setups, like heat pumps. Think of it like a spare tire—you don’t use it every day, but it’s there when your main system can’t handle the job.

Why people use it

People rely on EM heat when their primary heating system isn’t working well, usually during very cold weather. For example, heat pumps struggle in freezing temperatures, so EM heat kicks in to keep the house warm. It’s also used if the main system breaks down, acting as a temporary fix until repairs are done.

Basic examples

  • Cold snaps: If temperatures drop below freezing, a heat pump might not keep up. EM heat turns on automatically (or manually) to provide extra warmth.
  • System failure: If the heat pump stops working, EM heat can be turned on manually to avoid a freezing house while waiting for a repair.
  • Energy savings: Some people use EM heat sparingly because it can be more expensive to run, saving it for true emergencies.

  • EM heat is like a backup generator—it’s not the first choice, but it’s a lifesaver when you need it.

    Technical Details

    What It Is


    EM Heat, or Emergency Heat, is a backup heating mode found in heat pump systems. It falls under the category of auxiliary heating and is designed to provide warmth when the primary heat pump cannot operate efficiently, typically due to extremely low outdoor temperatures.

    How It Works


    EM Heat bypasses the heat pump and activates a secondary heating source, usually electric resistance coils or a gas furnace. When outdoor temperatures drop below the heat pump’s effective range (often around 25–30°F), the system automatically or manually switches to EM Heat. This ensures consistent indoor heating without overworking the heat pump.

    The technology relies on a thermostat or control system to detect temperature thresholds and trigger the switch. Some systems use sensors to monitor outdoor conditions, while others require manual activation.

    Key Components


  • Heat Pump: The primary heating and cooling unit.
  • Auxiliary Heating Elements: Electric resistance coils or a gas furnace.
  • Thermostat/Control System: Manages the switch between heat pump and EM Heat.
  • Temperature Sensors: Detect outdoor conditions to automate the process.

  • Common Use Cases


  • Extreme Cold Weather: When outdoor temperatures fall below the heat pump’s operational limit.
  • Heat Pump Malfunction: As a temporary solution during repairs or maintenance.
  • Energy Efficiency Control: To reduce strain on the heat pump during prolonged cold spells.
  • Manual Override: Users may activate EM Heat for rapid heating in emergencies.