Dwyer Series 1640 Floating Contact Null Switch

Part Number: Series 1640 Category:

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The unique electric switch design in the Series 1640 is another Dwyer Instrument, Inc. innovation. The Dwyer® Series 1640 Differential Pressure Switch resembles the Series 1630 switches. However, the Series 1640 is equipped with a single pole, double throw floating contact switch (not snap acting) so it functions as a null switch.

As the diaphragm moves in response to pressure changes, it moves the floating contact to cause switching action at two preset points with no switching action between these points. The “high” circuit will be closed when rising pressure differential reaches the preset level. The “low” circuit will be closed when falling pressure differential reaches the preset level.

A typical example of usage is to position motorized dampers when static pressure in a duct system reaches a desired maximum and reposition the dampers when the static pressure falls to a pre-established minimum. By using a Pitot tube sensing element the Series 1640 switch can serve in the same way to control air velocity and maintain a constant volume of air in a supply duct.


Product Applications

  • Damper positioning
  • Duct air control

Service : Air and non-combustible, compatible gases.

Wetted Materials : Consult factory.

Temperature Limits : -30 to 110°F (-34.4 to 43.3°C).

Pressure Limits : 10 psig (68.95 kPa) continuous, 25 psig (172.4 kPa) surge.

Switch Type : SPDT.

Electrical Rating : Non-inductive: 2.5 A @ 110 VAC, 1.5 A @ 220 VAC, 1 A @ 24 VDC, 0.5 A @ 110 VAC; Inductive: 1 A @ 110 VAC, 0.5 A @ 220 VAC, 0.5 A @ 24 VDC. (De-rate 70-80% for very slow pressure changes.)

Electrical Connections : 3 screw type, common, normally open and normally closed.

Process Connections : 1/8″ female NPT.

Mounting Orientation : Diaphragm in vertical position. Consult factory for other position orientations.

Set Point Adjustment : Screw type.Weight:4 lb 13 oz (2.18 kg).

Agency Approvals : CE.

  • Floating “null” switch supports applications requiring two set point actions such as open and close damper control
  • Visible set point indicator simplifies operation and trouble shooting
  • Large diaphragm provides low range accuracy providing precise control

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