The Dow Building (Oklahoma City): Cooling Tower Consolidation and VFD Retrofit

Project Overview

When the current owner purchased the Dow Building, the cooling towers were “on the list” to be replaced immediately. The existing setup consisted of two small units that were increasingly unreliable. We proposed a design that didn’t just replace the old machines, but simplified the entire mechanical plant by consolidating two towers into one high-efficiency Baltimore Aircoil (BAC) unit.

Solution Design: Consolidating for Long-Term Reliability

The original configuration was redundant but in an inefficient way: it had two fans, two gearboxes, and two motors—which meant double the potential failure points and twice the preventive maintenance workload.

The Power of VFD Control

One of the most significant upgrades in this project was the addition of a Variable Frequency Drive (VFD).

• On-Off Systems (The Old Way): Older cooling towers are often binary—they are either 100% on or 100% off. This causes “bang-bang” wear on motors and gearboxes, and leads to dramatic swings in chilled water temperature.
• VFD Modulation: With a VFD, we can run the fan at low RPM on cool Oklahoma spring days. If the discharge water is only a few degrees above setpoint, the VFD can ramp up to 30% speed instead of 100%, significantly extending the life of the belt and motor.
• Passive Cooling Energy Savings: The new BAC unit has so much surface area that on many days, we can cool the water just by running it over the fill without the fan even turning. This results in massive energy savings that show up immediately on the utility bill.

Project Challenges: Structural Engineering the Footprint

Consolidating from two towers to one isn’t just a plumbing challenge—it’s a structural engineering task. You cannot simply “place” a single large unit on top of the original two footprints.

Structural Beam Modifications

The original steel support beams on the roof were welded to match the footprints of the two original towers. Because the new, consolidated unit was larger and had different support points, we had to re-engineer the platform.

• Support Beam Gap: The middle beams from the old setup aligned, but the outside beams did not reach the support points of the new single unit.
• Custom Fabrication: We ordered custom steel I-beams that had to be lifted by crane and welded into the building’s structural frame before the tower could be landed.
• Weight Distribution: We had to verify the pounds-per-square-foot load on the roof structure to ensure the consolidated unit wouldn’t cause structural damage.

Execution Strategy: The Unpredictable Oklahoma Weather

The first scheduled day for the crane set was a classic Oklahoma “wind day.” At the height of the Dow Building’s roof, the gusts were creating dangerous updrafts and currents.

Safety Protocol: We have zero control over the weather, but we have 100% control over the “Go/No-Go” decision. Our crane partner, Allied, agreed that the current was too high. We called off the lift, waited 24 hours for the winds to die down, and completed the project safely under blue skies the following morning.

Assembly on the Roof: The “Flex” Factor

Like many large commercial units, the new tower arrived in sections. Because the tower frame isn’t rigid when suspended from a crane, it can flex and “tweak” during the lift.

• Alignment Difficulty: We spent several hours using specialized setting pins and pry bars to ensure the bolt holes lined up.
• Waterproofing: Between the upper and lower sections, we applied a specialized black sealant tape. If you don’t land the sections perfectly on the first try, the tape “grabs” and ruins the seal. We had to perform a reset twice to get it perfectly true and leak-free.

Business Protection: The “Pre-Lien” Lesson

An interesting byproduct of this project was a lesson in Oklahoma construction law for the building owner. After the Baltimore Aircoil unit was ordered, the manufacturer issued a pre-lien notice.

Business Tip: In Oklahoma, manufacturers of major equipment like cooling towers can file a pre-lien notice against a property owner to protect their right to get paid. This doesn’t mean the contractor is unreliable; it’s a standard business protection in the trades. Always work with a contractor who has established relationships with manufacturers and clear credit terms to avoid project delays or legal headaches.

Lessons Learned

1. Simplified is Better. Moving from two units to one reduces the long-term cost of ownership by eliminating half the moving parts.
2. Structural checks are mandatory. Never assume a new unit will fit the old beams. Footprint engineering is just as important as HVAC engineering.
3. Patience with the weather. In Oklahoma, “tomorrow is usually better.” Pushing a crane lift in high winds can lead to catastrophic equipment loss.

Technical Specifications

Full Project Gallery (16 Photos)

Your Facility’s Next Upgrade?

If your office building is managing multiple aging mechanical systems, consolidation might be the most cost-effective path to reliability. We provide full engineering, structural, and automation support for Oklahoma retrofits. Call (405) 223-9900 or request a proposal.

This case study represents a real-world project performed in Oklahoma City. Equipment specs and structural requirements vary by site.