On (b)(6) 2014, a dealership ((b)(6)) reported to midmark that a preva unit (serial no.(b)(4)) installed at (b)(6), separated from the wall.At the time of reporting, the dealership had already re-enforced and repaired the wall and had replaced the unit with one from factory stock.The dealership provided to midmark photographs of the damaged wall and stated that no person was injured when the unit separated from the wall.Investigation by the dealer field technician revealed that the affected unit had been improperly installed.The preva installation manual (00-02-1577) states that plywood is not an acceptable attachment material, and affected unit was attached to the wall using a plywood backer board.The preva installation manual also recommends that wooden studs be located initially by a stud finder device, then visually verified by opening the wall.The affected unit was attached using there screws, two of which were bolted into wooden studs and one inadvertently bolted into a gap between two studs.The use of plywood and inadequate location of studs led to insufficient attachment of the preva unit to the wall.
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