Water Central Heating pipework and controls

Building Regulation Part L 2010 introduced changed requirements for the control of new installations of water central heating and when replacing boilers to increase the energy efficiency of dwellings. It is important not to over heat any part of the dwelling and to switch the boiler and pump off when no heating is required.

In summary, for new installations in dwellings up to 150m² the requirement is to have at least 2 heating zones:, one of which being the living area (except single storey open plan dwelling where only 1 zone is required) with each zone controlled by a room thermostat and 1 timer controlling the whole system. As illustrated in Figs 1a & 1b (click either image for a larger illustration).

Typically with System Boilers, a multi-channel Programmer will be fitted so that the central heating and domestic hot water can be controlled by separate timers.

System Boiler System

Fig 1a - System boiler controls - dwelling less than 150m² 


Fig 1b - Combi boiler controls - dwelling less than 150m²

In dwelling larger than 150m², additionally to the above requirements, each zone has to have its own time controller - either its own individual timer or by using a multi-channel programmer.

Thermostatic Radiator Valves (TRVs) must be fitted to every radiator except those in the room containing the Room Stat and the bathroom.

Boiler Replacement

When replacing boilers, it's generally impractical to re-route pipework to produce separate zones so the requirement is limited to having a room thermostat and timer. Using modern, wireless thermostats and timers means these can be added relatively simply without too much disturbance to existing decoration.

In addition, where practical, it's good practice to install Thermostatic Radiator Valves (TRVs) to every radiator except the room containing the Room Stat and bathroom.

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