Project Brief

PepsiCo's Arlington, Texas facility handles bulk salt in two rooms: a Dump Room on the mezzanine, where salts are mixed and discharged by gravity, and a Fill Room directly below. Humidity in both rooms was affecting the salt and the final product, with the Dump Room reaching 80 percent relative humidity at 72°F. Working through AC Infinity, KeRi was engaged to find out why and to fix it, starting with a feasibility study and carrying the work through design.

KeRi surveyed and air-tested both systems, and neither was running as designed. The Dump Room air handler was moving 30 percent more air than its design, with its outside air damper closed and the room under negative pressure. The Fill Room rooftop unit was moving 60 percent more air than its design, taking in less than a third of its design outside air, cycling on two of its four stages, and holding standing water and organic growth in its drain pan. With the adjacent warehouse unconditioned and under strong negative pressure, roll-up doors that stay open for long stretches, and daily washdowns, both rooms were drawing in humid air faster than the coils could take it out.

KeRi's recommendation was to take the outside air load off the room units. A new dedicated outside air system pre-treats 6,000 CFM of outside air, removing moisture at a steady rate and freeing capacity for a planned Fill Room expansion. KeRi sized it against Arlington's 0.4 percent design dew point of 75.4°F two ways, 43 tons to hold the original 50°F dew point limit or 36 tons at 55°F, which would cut yearly operating cost by 25 to 30 percent, and put both to PepsiCo. The failing Fill Room unit was replaced with a new indoor air handler, AHU-14, with new controls, monitoring and alarms.

MEP Engineering Scope

What We Engineered

Study and design for the salt room dehumidification:

• Feasibility study with a field survey and airflow testing of both existing systems
• Dehumidification load calculations at the 0.4 percent design dew point, sized for two dew point limits
• New dedicated outside air system pre-treating 6,000 CFM of outside air
• Replacement of the Fill Room rooftop unit with a new indoor air handler, AHU-14
• Rebalancing of the Dump Room air handler, AHU-16, to its design airflow
• New controls with a monitoring and alarm point list
• Structural coordination for the new units on the mezzanine, and power for the new equipment
• Submittal review for the new air handler and dedicated outside air system

The Challenge

Humidity was reaching the salt, but the existing units were not simply too small. They were running far off their design airflow, taking in too little outside air, and fighting humid air pulled in through open roll-up doors from a warehouse under negative pressure, on top of daily washdowns.

Our Solution

KeRi measured before designing, then took the outside air load off the room units with a dedicated outside air system, replaced the failing Fill Room unit and rebalanced the Dump Room unit. Sizing the new system for two dew point limits gave PepsiCo a clear choice between tighter control and 25 to 30 percent lower operating cost.