A gas furnace does not have a dedicated “emergency heat” setting like a heat pump system. However, a gas furnace can serve as a backup heating source in a hybrid heating system that combines a heat pump and a gas furnace. In such a system, the gas furnace is used when the heat pump is unable to maintain the desired temperature, typically in extremely cold weather.
How Does a Gas Furnace Integrate with a Heat Pump?
Hybrid Heating System
In a hybrid heating system, the gas furnace acts as the backup heating source when the heat pump is not efficient enough to maintain the desired indoor temperature. This usually occurs when the outdoor temperature drops below a certain threshold, typically around 32°F (0°C).
Activation Conditions
The switch from the heat pump to the gas furnace is typically controlled by the thermostat. The thermostat may have an “emergency heat” or “auxiliary heat” setting, but this is not used to directly activate the gas furnace. Instead, the thermostat monitors the outdoor temperature and the system’s ability to maintain the desired indoor temperature, and it automatically switches to the gas furnace when necessary.
Settings and Controls
The thermostat manages the transition between the heat pump and the gas furnace based on predefined temperature thresholds. There is no specific “emergency heat” setting on the gas furnace itself; the thermostat is responsible for controlling the switching between the two heating sources.
Efficiency, Effectiveness, and Limitations
Efficiency
Gas furnaces are generally more efficient than electric heat strips but less efficient than heat pumps in moderate temperatures. However, in extremely cold weather, a gas furnace can be more cost-effective and efficient than relying on electric backup heat.
Effectiveness
A gas furnace is highly effective as a backup heating source because it can provide consistent and reliable heat, especially during prolonged periods of cold weather when the heat pump’s efficiency drops.
Limitations
The primary limitation of a gas furnace as a backup heating source is the higher operational cost compared to a heat pump in moderate temperatures. Additionally, the system’s overall efficiency and cost-effectiveness depend on the specific design and installation of the hybrid system.
Integration with Heat Pumps
Specifications and Installation
Hybrid heating systems that include a heat pump and a gas furnace require specific installation considerations to ensure seamless integration. This includes proper sizing of both the heat pump and the gas furnace, as well as the installation of a compatible thermostat.
Operational Costs
The operational costs of a hybrid system depend on the balance between the heat pump and the gas furnace. In general, the system operates the heat pump when it is most efficient and switches to the gas furnace during extremely cold weather or when the heat pump fails.
Conclusion
In summary, a gas furnace does not have a dedicated “emergency heat” setting, but it can serve as an effective backup heating source in a hybrid heating system that combines a heat pump and a gas furnace. The integration of these two heating sources provides a reliable and efficient heating solution, especially in cold climates.
Reference:
1. Family Handyman: What Is the Emergency Heat Setting?
2. Anthony PHC: Shut off your Heat Pump if you have a Gas Furnace for the Back Up Heat
3. The Spruce: What Is Em Heat on a Thermostat?
