Lennox 12W18 4 Ton Split System Air Conditioner Hard Start. Lennox goal is to provide contractors with high-quality HVAC solutions and replacement parts. This system includes changes and inventory updates to ensure peak performance. Lennox has a large line up parts and products for high-efficiency packaged rooftop units, split systems, HVAC controls, furnaces and indoor air quality products. This Lennox 12W18 4 Ton Split System Air Conditioner Hard Start is replacement part designed to increase the start time and relief the system from having a difficult time starting.