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Building Services Engineering 5th Edition Handbook

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

and,<br />

EL 3 = 1.3 × (50 + 4 + 1 + 3 + 1) m = 76.7 m<br />

Therefore,<br />

and,<br />

H 3<br />

= 9 m water = 0.1173 m water/m run<br />

EL 3 76.7 m run<br />

p<br />

EL 3<br />

= 0.1173 × 9807 N/m 3 = 1150.4 N/m 3<br />

While this pressure loss rate is available, a water main 15 mm in diameter would provide a<br />

flow of a little over 0.16 kg/s. Then, while the taps are shut, the storage tank would refill in:<br />

230 kg ×<br />

s<br />

0.16 kg × 1h<br />

3600 s = 0.4 h<br />

EXAMPLE 6.3<br />

A hot-water service secondary system is shown in Fig. 6.10. Estimate the sizes of the pipes<br />

and specify the pump size.<br />

Cold-water<br />

storage tank<br />

4<br />

Cold feed<br />

Vent<br />

1<br />

2<br />

1 Secondary pump<br />

Basin Bath Basin Basin<br />

1<br />

Hot-water storage<br />

indirect cylinder<br />

2 8 3 2<br />

2<br />

Secondary circulation<br />

flow and return<br />

Sink<br />

Basin<br />

Sink<br />

1<br />

2 3<br />

2<br />

Dimensions in metres<br />

6.10 Secondary hot-water service system for Example 6.3.

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