October_1965 — Page 30

LINES OF SIMILAR

AIR CHANGES IN RE-

SPECT OF SLOPES TO

RELATIVE

100% 80% 60%

QUTSIDE AIR

HUMIDITY

40% 30%

SENSIBLE HEAT GAIN IN SPACE

MOISTURE GAIN IN SPACE

20 30 40 50 60 70 80 90 100 DRY BULB TEMPERATURE

cases

In Hong Kong however the size of tank storage is limited (and in some that not allowed at all) so should water rationing be imposed only a minimum supply of water can be drained off from the tanks.

This limited storage means that the supply main feeding the tanks must be of sufficient size to deliver water at a rate equal to that being used in the building, as the smallness of the tanks invalidates their use as reser- voirs which could cope with the peak demands of the water users.

The possible restricted water hours in Hong Kong also means that the simultaneous demand for water in a building could be much higher than in other countries and the distribution pipework in a building has to be of a size to provide adequate water under these circumstances.

It is therefore extremely important that the simultaneous maximum de- mand for water in a building be care- fully assessed and the services design- ed accordingly, otherwise the building occupants could experience a failure of water supply at taps, etc.

In Hong Kong the use of well water for supplying cooling towers of air-conditioning plants and the flush water system for a building is com- mon practice but there are still cases where the well water pumps are in- correctly selected and arranged.

work of either sucking or ejecting water from the well bore some dis- tance below the pump.

A more satisfactory arrangement is to al- low the well pump to discharge water to a break tank which is 20% reasonably close to the pump and from this tank the water can by means of a separate pump be delivered to tanks at a higher level in the building.

10%

—MOISTURE CONTENT ō

In addition to well water, sea water is utilised in Hong Kong as a cooling medium for refrigeration ma- chinery and a supply source for toilet flush-

ing.

The use of this water necessitates the most selection of materials for

automatic controls whether they be confined to a simple safety valve for a boiler or a complete instrumentation room for remotely controlling all services for a large building. AL- though the controls and instruments provided for a large project may be extremely complex each device usual- ly comes within the groups given in Table 3.

Group 1. Controls and devices that are provided for safety purposes are essential in order to protect the build- ing, occupants and plant attendants.

Group 2. Although controls and instruments are provided to ensure the engineering services operate correctly they do in addition often prevent a wastage of fuel. A good example

would be the use of control ther- mostats and humidistats that form a part of an air-conditioning system. Without these controls the tempera- ture and humidity in the building could fall below design figures with consequent unnecessary use of electrical energy at the refrigeration plant.

a valves.

careful suitable pipework, pumps, etc., as Hong Kong sea water IS notorious as a Corro- sive agent unless speci- al measures are taken.

In addition to its use in connection with re- frigeration machinery and toilet facilities, sea water has been utilised with distillation plants to obtain fresh water for certain buildings in Hong Kong.

110 120

• F

130

Fig. 6.

The installation of a distillation plant does add to the complexity of the water services of a building in- as much as sea water, brine and dis- tilled fresh water equipment and pipes have to be accommodated in the building.

Unfortunately the number of buildings that can receive a sea water supply are limited due to their posi- tion relative to the sea front and the problems involved in installing pipe- lines under existing busy roads.

Instrumentation and automatic controls

Engineering services necessitate the application of instrumentation and

I

Building & curve number

2

% heat loss or gain due to conduction

Group 3. The extent of devices to be provided to prevent fuel wastage does depend on the value of the fuel and the capabilities of the plant operators to interpret the instruments provided. Should for instance a plant use a relatively inexpensive fuel (e.g. waste heat from an industrial process) and the understanding of the plant operators is rather limited, then it may not be economical to install com- plicated expensive instruments as these would not be fully understood or used.

Group 4. Thermometers, pressure gauges, etc. that are provided for fault analysing are essential for almost all services and plants. For certain buildings such as hospitals, cold stores etc. it is imperative that should a ser- vice or plant fail to function correctly then the fault must be speedily de- tected and repaired.

Group 5. There has been consider- able controversy among engineers as to the type and number of instru- to be provided at a central

ments

TABLE No. 1.

3

% heat due to occupants electric lights,

etc.

4

Temperature obtained when providing 12 air changes per hour, outside air being 85°F dry bulb

5

Temperature obtained if no ventilation provided

1.

50%

50%

89.0 °F

95.0 °F

2.

40%

60%

91.75 °F

100.0 °F

A common cause of an unsatisfac- tory water yield from a well is the arrangement whereby the well pump work of either sucking or ejecting in the building in addition to its prime

3.

30%

70%

93.8 °F

108.3 °F

4.

20%

80%

98.0 °F

125.0 °F

5.

10%

90%

104.0 °F

175.0 °F

74

Far East Architect & Builder October, 1965

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