Series BYDS Bypass Damper Switch

Brand: Dwyer Instruments, LLC

The Series BYDS Bypass Damper Switch is designed to control motorized bypass dampers.

As individual zone dampers open and close, the system static pressure will rise and fall. In order to maintain proper airflow and static pressure through the HVac system, a bypass system incorporating a floating type motorized damper and a static pressure control should be incorporated.

A typical on/off pressure switch cannot operate in this application due to the high cycle rate that would result, eventually causing contact burnout. The BYDS static pressure control is equipped with a solid-state switching and timing circuit to enhance operation and improve long-term reliability in this demanding application.

Control Operation
The BYDS Bypass Damper Switch is designed for use with a three wire floating point damper actuator used to control the static pressure on zone control systems requiring motorized bypass dampers. A bypass damper, bypasses air from the discharge air side of the HVAC unit back in the return air side. The air flow is modulated in order to maintain a constant static pressure in the system as individual zone dampers open and close.

The static pressure control is equipped with solid-state switching which dramatically increases the life of the control. On an increase in static pressure the BYDS will send 24 volts out and start the actuator to drive open. When the static pressure reaches set-point the actuator will stop.

After a ten second delay the actuator will start to drive the damper closed if there has not been an increase in static pressure. A green LED indicates when the damper is in the open position or being driven open. A 24 Vac transformer is required to power the BYDS control and damper actuator. The unit includes tubing and two static pressure probes.
  • Units include 2 plastic static pressure tips and 7 ft. (2.1 m) of PVC tubing.
  • Adjustment knob changes switching pressure easily with a pressure gage reducing components for application.
  • Low cost device makes it an excellent solution in BAS and HVAC applications requiring duct control and monitoring.
  • Relay contact allows simple integration with DDC or building systems.


Adjustment Type

  • Field Adjustable

Approvals & Certifications

  • CE
  • RoHS

Cover - for Local Enclosure

  • Polystyrene

Deadband, Approximate

  • Inches WC: 0.05 to 1.4

Diaphragm Material

  • Silicone Rubber

Electrical Connectors

  • 1/2” NPT Female
  • Screw Terminal Block. M20 x 1.5 with Cable Strain Relief

Electrical Rating

  • 1 A at 24 Vac

Enclosure, Body Material

  • PA 6.6 & POM

Environmental Protection

  • IP54
  • NEMA 13 / IP54


  • Green Indication Light


  • Diaphragm in Vertical Position
  • Vertically, with Pressure Connections Pointing Downwards

O-Ring Material

  • Silicone Rubber

Operating Temperature

  • 0° to 50° C (32° to 122° F)

Proof Pressure

  • Inches WC: 40

Set Point - Decreasing

  • Inches WC: 0.08 to 20.0

Set Point - Increasing

  • Inches WC: 0.08 to 20.0

Switch Type

  • SPDT

System Pressure

  • 40” WC
  • Inches Hg: 2.95

Tube Connection

  • 5/16˝ (7.94 mm) Outside Diameter Tubing, 1/4˝(6.0 mm) Inside Diameter Tubing

  • Air Filter and Ventilator Monitoring
  • Industrial Cooling Circuits
  • Fire-protection Damper Control
  • Ventilation Duct Monitoring
  • Fan Heater Overheating Protection
  • Heat Exchanger Frost Protection
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