Standard and Custom FFU’s
Standard Units Do Not Have Motor Sensors
Options
Dry Contact Pressure Sensor
To insure that each fan in the system is producing adequate pressure a dry contact diaphragm style pressure switch is employed. It measures the differential pressure between the fan inlet and ambient. The switch can be either normally open or normally closed. When adequate pressure is sensed, the condition of the switch changes. The status of the sensor is then reported via a light or to a connector.
Cleveland Controls Model DFS–221 (pdf)
Reporting When a High Pressure Condition Has Been Reached
A pressure switch that reports when the internal differential pressure reaches a pre-set limit (as in the case of HEPA/ULPA filter loading over time) the Cleveland Controls AFS-298-112 is provided. The status of the sensor is then reported via a light or to a connector.
Reporting When Either a High and Low Pressure Condition Has Been Reached
Two dry contact diaphragm style pressure switches to report via switch closure with a local display. One that reports when the internal differential pressure reaches a pre-set limit (as in the case of HEPA/ULPA filter loading over time), and a second that reports if a minimum differential pressure has not been kept (as in the case of the FFU motors ceasing to function due to loss of power) The local display is a magnahelic gauge on the Dwyer A3000. The position of the dry contact(s) is then reported via a light(s) or to a connector.
Reporting Differential Pressure as a 4-20 ma Value
Same as AFS series, above, but with the addition of a 4-20 ma output proportional to the actual pressure being measured.
Having an Analog Visual Display of the Differential Pressure
A differential pressure gauge can be added to track filter loading. The gauge itself can be mounted on the side of the FFU, in an external box (often with the reporting lights), or shipped loose for attachment by others.
Dwyer Magnehelic® Differential Pressure Gages – Indicate Positive, Negative or Differential, Accurate within 2%