It is essential for the healthcare of a boiler for an automatic bypass valve to be fitted as part of the heating system. A bypass is required to ensure a constant minimum flow rate through the heat exchanger and to dissipate heat on pump overrun. All modern boilers are ‘low water content’ and require a constant flow through them to prevent overheating.
This is particularly important if your heating system includes a large number of Thermostatic Radiator Valves (TRVs) as flow rate is reduced when TRVs start to close or are shut off completely. In this situation the automatic bypass valve will start to open to maintain the required water flow through the boiler. Using an Automatic Bypass Valve is also likely to reduce noise in systems caused by excess water velocities.
Alpha combination boilers already incorporate an automatic by-pass valve and for regular (heat-only) and system boilers your qualified Gas Safe registered engineer will be able to advise what is needed for your system to meet current Building Regulations.