Types of Slant/Fin Boiler Air Flow Switches

Air Flow Switch

• The function of the air flow switch in a boiler is to monitor air movement in the system. Most air switches have a sail icon on the switch and many boiler manufacturers, including the Slant/Fin Company, use air flow switches produced by other companies.

McDonnell & Miller

• The flow switches used in Slant/Fin boilers are manufactured by the McDonnell & Miller Corporation. These switches have a specific number associated with the McDonnell & Miller Corporation that is different from the Slant/Fin boiler model number. Most commonly, McDonnell & Miller Corporation flow switch numbers used by Slant/Fin are FS8V and FS4-3T3-1.

Slant/Fin Boiler Model Numbers

• McDonnell & Miller flow switches are used in a few different Slant/Fin boilers, including the EH-40 model and all models from EH-8 through EH35. The McDonnell & Miller flow switch FS8V should be used with the Slant/Fin EH-40 model and the McDonnell & Miller FS4-3T3-1 flow switch should be used with the Slant/Fin boilers EH-8 through EH-35.

Pipe Size and Length

• To work correctly, the flow switch in the boiler should be between 1 ¼ inches in size and a minimum of 8 ½ inches for the Slant/Fin boiler EH-40 and the McDonnell & Miller FS8V switch. A pipe size of at least 1 inch with a minimum length of at least 6 ½ inches should be used with the Slant/Fin models EH-8 through EH-35 and the McDonnell & Miller switch FS4-3T3-1.