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6.0 System Details - Page 11
6.6 System Filling and Pressurising
1. A filling point connection on the central heating return
pipework must be provided to facilitate initial filling and
pressurising and also any subsequent water loss
replacement/refilling.
2. The filling method adopted must be in accordance with all
relevant water supply bye-laws and use approved
equipment.
3. Your attention is drawn to: IRN 302 and Byelaw 14.
4. The sealed primary circuits may be filled or replenished
by means of a temporary connection between the circuit and
a supply pipe, provided a 'Listed' double check valve or
some other no less effective backflow prevention device is
permanently connected at the inlet to the circuit and the
temporary connection is removed after use (Fig. 9).
6.7 Expansion Vessel
(Central Heating only)
1. The appliance expansion vessel is pre-charged to 1 bar
2
(10 lb/in
). Therefore, the minimum cold fill pressure is 1 bar.
The vessel is suitable for correct operation for system
capacities up to 125 litres (27.5gal). For greater system
capacities an additional expansion vessel must be fitted -
refer to BS 7074 Pt 1.
6.8 Pressure Relief Valve (Figs. 10 & 11)
1. The pressure relief valve is set at 3 bar, therefore all
pipework, fittings, etc. should be suitable for pressures in
excess of 3 bar.
2. The pressure relief discharge pipe should be not less
than 15mm dia, run continuously downward, and discharge
outside the building, preferably over a drain, It should be
routed in such a manner that no hazard occurs to occupants
or causes damage to wiring or electrical components. The
end of the pipe should terminate facing down and towards
the wall.
3. The discharge must not be above a window, entrance or
other public access. Consideration must be given to the
possibility that boiling water/steam could discharge from the
pipe.
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