A fossil fuel kit is a control device used in Dual-Fuel System setups to manage the handoff between an electric heat pump and a gas furnace. Because a heat pump's indoor coil usually sits on top of the furnace, the kit ensures the furnace and heat pump never run at the exact same time, which could damage the compressor. This kit acts as the brain that monitors outdoor temperatures and decides which heat source is the most efficient to run. Many of our ACIq systems can be upgraded with these kits for maximum versatility in cold climates. You can find these specialized controllers in our Accessories-Kits section. By switching to the gas furnace when the air is too cold for the Heat Pump Condenser, the kit keeps your home warm while saving you money on electricity. It is the essential interface for anyone looking to combine the power of gas with the efficiency of electric. It represents the ultimate in hybrid home heating technology.