Danfoss Automatic Bypass Valve 22mm

The automatic bypass valve 22mm is a self-acting valve that is simple to set. It looks after the boiler and pump by making sure some water is always moving, however many radiator valves are shut.

When to fit an automatic bypass valve 22mm

Low water content boilers do not like low flow. If every TRV closes, the heat exchanger can overheat and the boiler cuts out or cycles. A bypass gives the water a route back, so flow stays above the minimum. It also cuts down on the noise you get when a pump pushes against closed valves.

Fit it across the flow and return, after the pump and before the zone valves, unless the boiler manual says something different. Some modern boilers have their own bypass, so check before you add another. Set it with the system hot and most radiators closed, then adjust until flow is steady and the system is quiet. Fit it where you can get to it again.

Specification

• Sizes: 22mm
• Suitable for: Central heating systems with TRVs, fitted between flow and return

Common Questions

What does an automatic bypass valve do?

It opens as pressure across it rises, letting water go from flow to return when radiator valves close. That keeps a minimum flow through the boiler.

Does every heating system need a bypass?

Not every one. Many modern combi and system boilers have one built in, so check the boiler manual before fitting another.

How do I set the bypass?

With the boiler and pump running and most radiators closed, open the setting until the pump noise settles and the boiler stays stable. Leave the final check to the heating engineer.

Heating spares at our Glasgow trade counter

This valve is listed under automatic bypass valves, alongside the other types.

Visit the Plumb Parts trade counter at 555 South Street, Glasgow G14 0QX, Mon-Fri 8am-5pm or Sat-Sun 8am-1pm. Ordering online is the other option.