Efficient Combustion Air Solutions: Fan in a Can Combustion Air Systems for Oil and Gas Heating Appliances

The Fan in a Can CAS3 and CAS4 diffuse the outside air into the room near the burner to ensure adequate air for efficient combustion.

The CAS-3 and CAS-4 models (now known as CAS 34U) are designed to provide combustion air for appliances when direct connection to the burner is not possible (when the appliance is located in a confined space). According to NFPA 54 and NFPA 31, an engineered system such as a CAS-3, 4, 6 or 7 may be used to overcome the lack of air in a confined space.

The CAS-4MV is for use with 750mV power pile gas appliances. Each is designed for optimum safety and includes a proving device that won’t allow the burner to engage without the Fan-in-a-Can operating. Multiple units or additional controls are required for multiple appliance installations.

The Fan in a Can, Jr., model CAS-4Jr. is designed for gas appliances up to 110,000 BTU/hr input. A 4 intake Air Hood (IAH) is included along with mounting brackets to secure the Fan-in-a-Can, Jr. to a wall. It may be used with a residential water heater with the addition of control kit CK-20 FV/FG.

How Does the Fan In A Can CAS3 and CAS4 Work?

1. The thermostat (wall thermostat, or aquastat) calls for heat and energizes a relay which activates the Fan In A Can CAS unit. After the CAS fan has come up to speed, an internal air pressure switch closes and completes the circuit to allow the burner to fire. If the appliance is power vented, the venter and CAS activate simultaneously. After the CAS comes up to speed, a pressure switch in the unit closes and allows the appliance to fire.
2. After the heating requirement has been satisfied, the thermostat circuit will open and deactivate the burner and CAS unit.
3. For power vented systems with a post purge device, the power venter and CAS operate for a period of time after the burner has shut off to purge remaining flue gases from the vent system.