Construction: The curb consists of square section casing fabricated from pregalvanised steel sheet, containing a vertical assembly of acoustic splitters and liners. The splitters have pre-galvanised steel frames and the absorbent material is resin bonded mineral fibre with an erosion resistant facing. An impervious moisture assessments lining is available for moist air applications. The use of the lining also allows the curb to be low pressure steam cleaned. Some reduction in attenuation due to the lining will be experienced. The skirts and flanges are also produced from galvanised sheet steel. Lifting Lugs are provided on all sizes.
Mounting: The curb may be mounted on the builders’ roof curb, purlin box surrounding the roof opening in one of two ways
Recessed Mounting: For this method a skirt is attached to the outside of the casing for mounting the unit within the roof opening. The position of the skirt can be factory set, to offer a range of the sound attenuating curb above or below the roof opening.
Base mounting: The unit is positioned on top of the builders’ roof curb with the unit covering the timber. Coachscrews and sealing washers are provided with both forms of mounting, for assembly to the builders’ curb. Customers should provide flashing where wooden curbs are exposed.
Electrical connection: Electrical connections to the roof unit fan motor terminal box may be taken from a junction box installed adjacent to the sound attenuating curb via a flexible conduit led up through one of the curb airways.
Order Details: When ordering a sound attenuating curb state the WAC size and whether to be Recessed Mounting or Base Mounting. If for recessed Mounting state dimensions F - necessary for the setting of the mounting height. See drawing opposite. When no dimension is given the maximum dimension F is supplied. When required for use with roof units employing flameproof motors, please specify as “WACF’ plus the size. The use of flameproof motors necessitates the rearrangement of the splitters with some loss of attenuation.