IS 3963 : 1987 Roof extractor units

1 Scope

1.1 This standard specifies the requirements and tests for roofextractor units in which the extraction fan is driven by anelectric motor operated from either single-phase supply voltage notexceeding 250 volts or three-phase supply voltage not exceeding 440volts. It covers This types of roof extractor units:

a) Vertijet type in which there are two or more shutters (onthe top of the cowl) which open only when the fan is operated andthe air leaves the weather-protection casing vertically upwardssubstantially parallel to the axis of the fan impeller, and

b) `Cowl type in which the top of the weather-protection casingis closed and the air driven vertically upwards by the fan impellerrebounds from the top of the cowl and leaves the casing downwardsthrough openings at its sides

1.2 This standard also covers speed regulators, if any,associated with the extractor fans.

1.3 This standard does not cover units in which the fan impelleris not directly driven by the motor.

2 References

IS 2 :1960Rules for rounding off numerical values

IS 302 :1979General and safety requirements for householdand similar electrical appliances

IS 585 :1962Voltages and frequency for transmission anddistribution systems

IS 1248 : Part 1 :1983 Specification for direct actingindicatinganalogue electrical measuring instruments andtheir accessories:Part 1 General requirements

IS 1271 :1985Thermal evaluation and classification ofelectrical insulation

IS 1401 :1970 Accessibility test probes

IS 1709 :1984Specification for capacitors for electric fanmotors

IS 1885 : Part 55 :1981 Electrotechnical vocabulary:Part 55 Electric fans