- Easy to set, self acting flow controller 
- Opens on rising differential pressure 
- DN15, DN20, DN25 
- Setting range of 0.05 to 0.5 bar 
- Internal/External thread variants 
- Improves system efficiency 
- Maintains minimum flow rates through boiler and pump 
- Essential in low water content boiler systems 

The AVDO range of automatic bypass valves can be used as either differential pressure controls or to provide a minimum flow through a system. 
Many boiler manufacturers are now insisting that a bypass be fitted in all installations to ensure that the volume of water circulating through the boiler does not fall to below a predefined minimum, regardless of the load on the system. Recognising the energy efficiency advantage of such controls the Building Regulations now require in both new-build and boiler replacement contexts, where a bypass is specified by the boiler manufacturer, that an automatic bypass is fitted. Automatic bypass valves improve system efficiency by opening only when there is a need to bypass water, this usually occurs at times of part load when radiator thermostats in the system are partly closed and water flow around the boiler is restricted. In addition to ensuring adequate flow around the boiler, automatic bypass valves also prevent pump pressure from climbing significantly above design levels, thus reducing the risk of noise in the system. 
Available in a variety of sizes, the capacity of this range of valves is very high with large but linear changes in water throughput for relatively small increases in differential pressure. This 
allows a 15mm valve to be used in situations where 22mm valves are normally required. 

Setting Range 0.05 - 0.5 bar 
Max. differential pressure 0.5 bar 
Operation pressure PN 10 
Max. flow temperature 120°C 
Max. leakage at closed valve 50 l/h