No_4_May_and_June__1950 — Page 14

G.E.C.

WOODS

ROOF EXTRACTOR UNIT

The

There is a vast difference between the ventilating capacity of Woods Roof Extractor Unit and that of the ordinary roof cowl. Woods Unit gives guaranteed air displacement. Its superiority can be readily appreciated when the relative effectiveness of natural and mechanical draught ventilation is compared.

The less difference there is between the temperature of the inside and outside air, the less air movement there will be through the natural cowl. It follows that in hot, windless weather, when ventilation is most required, the natural roof cowl is liable to be ineffective. Conversely its extraction capacity is greatest in wintry weather when minimum air changes are needed. Woods Roof Extractor Unit, however, incorporates an efficient exhaust fan when provides effective ventilation at a guaranteed rate and gives positive control of air changes. Yet the initial cost of this unit compares very favourably with that of natural cowls and it cost little to operate.

LOW RUNNING COST-Relatively little power is consumed by Woods Roof Extractor Units. Take for example the ventilation of an industrial building 140 ft. x 150 ft. x 25 ft. average height. If six air changes an hour are to be provided, the total air movement required for summer ventilation will be 3,150,000 cu. ft. per hour, or 52,500 c.f.m. (cu. ft. per minute). This rate of air movement can be obtained approximately with eight No. 30a Roof Extractor Units, each extracting 6,520 c.f.m., and the total power consumption of the eight units will be only 3.50 kilowatts, or units, of electricity per hour.

REGULATED VENTILATION_Ventilation by Woods Roof Extractor Units can be regulated to suit the weather. The performance of a number of the units can be controlled by means of fan speed regula- tion, which enables the rate of air movement to be reduced in cool weather or increased in hot weather. Alternatively control of air changes, and of heat loss, can be effected by switching off some or all of the units in cold weather. When the units are switched off there will be a small amount of natural ventilation, but not sufficient to cause serious heat loss.

INFREQUENT SERVICING—The units require little attention. Continuous running with little ser- vicing is one of their features. Under normal condi- tions the only attention required is re-lubrication once in 12 months.

SOLVES ADVERSE WIND PROBLEMS The ventilation of buildings in very exposed positions by means of wall-mounted exhaust fans may involve difficulties owing to the restriction of fan output caused by adverse wind pressures.

The right answer to such conditions is the Roof Extractor Unit. The performance of the unit will actually be improved by strong winds, partly because of the negative pressure above the roof caused by wind velocity, and partly by the additional extraction effect produced by wind blowing through the extractor cowl.

CONSTRUCTION—Woods Roof Extractor Unit incorporates a cowl of high aerodynamic efficiency, designed for mechanical extraction with a minimum restriction of fan performance. Alternative types of bases are supplied for flat roofs, roof slopes, or ridge mounting. The bases have flanges of ample width for bolting to roof members. To facilitate water-

proofing in erection, the bases are fitted with a flash- ing skirt under which the flashing is tucked.

are

FANS The extraction fans incorporated in the units are standard Woods propeller fans, giving high air deliveries in relation to power consumption. The driving motors-designed specifically for fan duties- manufactured completely in the Woods of Colchester factories. Totally enclosed and liberally rated, the motors are insulated to withstand exacting conditions of heat and humidity. Standard motors are suitable for continuous operation in ambient temperatures averaging 105 deg. F. with peak temperatures up to 112 deg. F., or down to -54 deg. F.

To minimise the possibility of overheating, the motors are designed for a temperature rise of only 65 deg. F., as against the rise of 90 deg. F. permitted by the British Standard specification for totally enclosed machines. All motors are fitted with ball bearings and are tapped for conduit entry.

Flameproof Fans-If Roof Extractor Units are required for handling inflammable atmospheres, Buxion Test flameproof fans can be supplied. Prices on request.

THE BRITISH GENERAL ELECTRIC COMPANY, LTD. Queen's Building, Hong Kong

Telephone 31131-2-3

REPRESENTING

Cable "GECHONG"

THE GENERAL ELECTRIC COMPANY, LTD. OF ENGLAND

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