Automatic bypass control AVDO

  • Overview
  • Features and benefits
  • BIM drawings
  • Documents
  • Tender text
  • Contact

AVDO is a self-acting constant flow control primarily used either to maintain minimum flow rates through e.g. a low-capacity gas boiler or to
control the differential pressure in a central heating system.

Features and benefits

opens on rising differential pressure 

has a setting range of 0.05 - 0.5 bar

is dimensioned for pressure stage PN 10, max. 120 °C 

DN 15 and DN 20

Operates without impulse tubes 

BIM drawings


Type Name Language Valid for Updated Download File type
Data sheet Automatic bypass control AVDO English Multiple 31 Mar, 2011 748.4 KB .pdf
Data sheet Automatic By-pass Valve AVDO English United States 14 Apr, 2010 433.9 KB .pdf

Tender text

  • Bypass valve are to be selected on the required bypass flow rate and opening pressure loss 
  • The valves shall be capable of the required opening pressure within the published spring range 
  • The valves shall be installed with a partner valve to enable bypass flow measurement and flow limiting if necessary 
  • The partner valves shall be fixed orifice in DN15-50 and variable orifice in DN50 (high flow) to DN400 


  • The valve shall be installed between flow and return in accordance with the flow direction shown on the valve casting 
  • The partner valve shall be on the return, just after the bypass valve, and within the impulse tube loop. If an installation schematic is required please contact your Danfoss representative 

Commissioning Method 

  • Set up the pump and system to deliver the conditions where bypassing should occur. This is the pump minimum flow or defined low flow rate 
  • Measure the flow rate on the partner valve. If you have an excess, reduce the flow rate on the partner valve. Record the flow rate in the commissioned condition 
  • Turn the spring setting mechanism on the valve until the calculated opening pressure loss is set 
  • If the valve is open, turn the mechanism until it is just closed. This point just between open and closed is the setpoint. Record the pressure setting as the actual opening pressure loss 
  • Open the system to design flow rate and operate as normal 
  • The valve will remain close in high load conditions and open in low flow conditions 


Experts within Heating 
Greg Tracy has been working in the HVAC industry for the last 15 years. Having worked at Danfoss for 10 years, Greg managed the Danfoss Underfloor Heating division in the UK. For the last 5 years he has been working and managing the Danfoss HVAC division with consultants and contractors on some of Londons most prestigious Commercial buildings.

Greg Tracy
Send Greg an email 
+44 1234364621