Technical data

© MHS Boilers Ltd
221106 Draft Copy E&OE
16
Filling The System
The Initial filling of a sealed heating system, and subsequent refilling, must be by a
method that has been approved by the Water Regulation Advisory Scheme (WRAS) for
that type of heating system.
i.e. Domestic (
In-House ) Fluid Category 3 ( C-3 )
Non Domestic (Other than
In-House ) Fluid Category 4 ( C-4 )
For Category 3 systems, the approved method of filling must comprise of the following
components in the arrangement shown;
• Control Valve incorporating a Double
Check Valve on the Mains Cold Water
pipework.
• Temporary Connecting Hose, which must
be disconnected after use.
• Control Valve, on the heating system.
For Category 4 systems, the approved method of filling must comprise of the following
components in the arrangement shown;
• Control Valve.
• Strainer.
• Verifiable Backflow Device with Reduced
Pressure Zone (RPZ Valve)
• Incorporating a ‘Type BA’ Air Gap.
• Tundish.
• Control Valve.
Further more, in accordance with BS 6644: 2005 system with an input greater than
70kW (nett), an automatic water replenishment unit shall be installed to automatically
replenish any lost or evaporated water.
Please refer to BS 6644: 2005 for allowable water replenishment methods for use with
sealed/pressurized heating systems.
For information on a comprehensive range of pressurization units that comply with
current British Standards and WRAS Regulations, please contact MHS Boiler Sales.
Expansion Vessel
In accordance with BS 6644: 2005, WRAS Regulations, and Local Authority Water
Regulations, as applicable, the installer shall install a suitably sized, and approved,
Expansion Vessel to ensure that the water capacity of the system has ample expansion
capacity.
The location of the expansion vessel shall only be isolatable from the system via a
Lockable Type Service Valve, which shall be locked in the
OPEN position, to prevent
accidental isolation.