Field Controls 46525600 CAS-4JR Fan In A Can Up To 110,000 BTU 24V What's Included: 1) CAS fan unit 1) 4" galvanized intake air Vent Hood 2) Mounting brackets to secure the CAS to a wall 2) Wire/conduit connector(s) 1) Instruction Sheet This product is designed for use with any natural gas or LP burning furnace, water heater, or boiler with a 24 VAC control system. It may be used with a residential water heater with additional hardware. It may also be used with more than one appliance. The CAS unit mechanically draws air into a structure and disperses it near the combustion air intake of an appliance. Refer to Diagram A and Table 1 for guidance in setting up the CAS system based on the size and length of the connecting ductwork and the input rating of the appliance.