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Building Services Engineering 5th Edition Handbook

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Hot- and cold-water supplies 183<br />

Overflow<br />

Automatic<br />

air vent<br />

Cold-water<br />

storage tank<br />

Filtered overflow<br />

Cold-water<br />

services<br />

Sealed drinking water<br />

storage tank<br />

Drinking water<br />

Boosted riser<br />

Pressure controller<br />

operates compressor<br />

and pump<br />

Compressed air<br />

Safety valve<br />

Air compressor<br />

Mains<br />

pressure<br />

drinking<br />

water<br />

Water level limits<br />

Drain<br />

Incoming<br />

water main<br />

Duplicate pumps<br />

and non-return valves<br />

Drain<br />

6.1 Pneumatic water-pressure-boosting system for tall buildings.<br />

in Fig. 6.1. Float switches in the storage tanks operate the pump to refill the system and minimize<br />

running times to reduce power consumption. A delayed-action ball valve on the cold-water<br />

storage tanks can be used. This delays the opening of the ball valve until the stored water<br />

has fallen to its low-level limit. System pressure is maintained by a small air compressor and<br />

pneumatic cylinder. The controller relieves excess pressure and switches on the compressor when<br />

the air pressure falls. During much of the day, water is lifted pneumatically at much lower cost<br />

than if it were pumped.<br />

Cold-water storage to cover a 24-h interruption of supply (CIBSE, 1986) ranges from<br />

45 l/person for offices to 90 l/person for dwellings and 135 l/person for hotels.<br />

Hot-water services<br />

Hot water can either be generated by the central boiler plant and stored, or produced close to<br />

the point of use by a more expensive fuel.

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