What is a forced draft fan

Forced Draft Fan, IFGR System, Miscellaneous/Safety Limits

Forced Draft Fan Assembly

  • Forced Draft Fan – Chicago Blower, Arrangement 4, airfoil centrifugal type fan with inlet vortex control damper (Shipped loose for field mounting on the windbox or remote mounted, depending on burner size)
  • Fan Motor – 1800 RPM, TEFC type, 460 VAC / 3 phase / 60 hertz (Part of fan assembly)
  • High Suction Pressure Limit Switch – (Part of fan assembly)
  • Fan Differential Pressure Limit Switch – (Part of fan assembly)
  • Forced Draft Damper Open Switch – (Part of fan assembly)

Miscellaneous/Safety Limits

  • Excess Boiler Pressure Switch – (Factory mounted on the windbox)
  • High Boiler Pressure Switch – (Factory mounted on the windbox)
  • Purge Air Flow Switch – (Factory mounted on the windbox)
  • High Furnace Pressure Switch – (Shipped loose for field installation)

Induced Flue Gas Recirculation

  • IFGR Inlet Box with fresh air damper with modulating electric or pneumatic actuator – (Shipped loose for field installation)
  • IFGR Flow Control Damper – Flow control damper with modulating electric or pneumatic actuator (Shipped loose for field installation)
  • IFGR Stack Scoop – (Shipped loose for field installation)
  • High Temperature IFGR Duct Gaskets (4) – Not shown in the schematic above (Shipped loose for field installation)
  • High Temperature IFGR Mixing Box Gasket (1) – Not shown in the schematic above (Shipped loose for field installation)

Options

FD1
Forced Draft Fan Silencer (Only applies to fans with a noise level of 85dBA or greater) – Silencer field mounted on the forced draft fan inlet to reduce the noise level emanating from the fan inlet to 85 dBA at 5 feet.

FD2
Forced Draft Fan Motor Starter – Includes a combination motor starter with overloads and a fusible disconnect in a NEMA 12 enclosure (Shipped loose for field installation).

FD3
Faber Low Draft Cutout – Necessary on installations where the furnace operates under a negative pressure. This system consists of a draft sensing element, an auxiliary relay, a time delay relay, a terminal strip, and an indicator light, packaged in a NEMA 12 enclosure. The indicating light is energized when a low draft condition exists in the furnace. The low draft cutout contact is wired directly into the burner safety limits circuit. This contact opens after a low draft condition has existed for the adjustable time delay period, which shuts down the burner on a safety limits failure. The time delay is set during commissioning, usually 4 to 8 seconds, and the setting is protected with a tamper proof cover.

NEMA 4
Changes items 3, 4, 6, 7, 8 and 9 to weatherproof (NEMA 4). If option FD3 has been purchased, the enclosure included with the option will be changed to NEMA 4. If option FD2 has been purchased, the FD fan motor starter will be supplied in a NEMA 4 enclosure.

Notes

If the available FD fan power supply is other than 460 vac/3 phase/60 hertz, enter (s) in the position 13 on the burner model number and note the available FD fan power supply on the burner package specification sheet.

IFGR system, items 10, 11, 12, and 13, supplied when necessary to meet project emission requirements.