Overview

GRR Cooling Experts completed a full air handling unit replacement, replacing the existing AHU with a new double-wall system designed for 16,000 CFM at 6.0 in. ESP.

The new AHU combines two-stage filtration, steam preheat and chilled-water coil sections, a fresh-air and return plenum, and four direct-drive EC blowers within one complete replacement package.

The project required demolition of the existing air handling unit, disconnection of existing piping, ductwork, and electrical service, and installation of the new AHU into the existing mechanical infrastructure.

The video below documents the replacement sequence, including demolition of the existing AHU and installation of the new 16,000 CFM double-wall system with four direct-drive EC blowers.

The Challenge

A complete AHU replacement requires more than replacing one fan or one internal section.

The existing fresh-air plenum, filter section, preheat coil section, chilled-water coil section, and blower section had to be disconnected, demolished, removed, and disposed of off-site before the new equipment could be installed.

Existing-building HVAC replacements depend on more than equipment selection. Access, duct geometry, piping, electrical capacity, and shutdown planning all shape the final solution. See our HVAC retrofit engineering guide for existing buildings for the broader planning framework.

The new AHU therefore had to be configured around the existing mechanical system while providing the required 16,000 CFM airflow at 6.0 in. ESP.

The Solution

GRR installed a new double-wall painted AHU configured as a complete air-handling system replacement.

The project scope included:

🔹 Fresh-air and return plenum with two new dampers and one access door
🔹 Two-stage filtration using V-bank and 2" pleated filters
🔹 Two new steam preheat coils
🔹 Two new 6-row chilled-water coils
🔹 Stainless-steel gravity drain pan
🔹 Four direct-drive EC blowers
🔹 Gravity backdraft dampers
🔹 Removal of the existing AHU and associated internal sections
🔹 Disconnection of existing steam and chilled-water piping
🔹 Disconnection and securing of intake and discharge ductwork
🔹 Disconnection of existing electrical service

System Specifications

🔹 Airflow: 16,000 CFM
🔹 External Static Pressure: 6.0 in. ESP
🔹 AHU Construction: Double-wall, painted
🔹 Fan Configuration: Four direct-drive EC blowers
🔹 Filtration: V-bank + 2" pleated filters
🔹 Heating: Two steam preheat coils
🔹 Cooling: Two 6-row chilled-water coils
🔹 Drainage: Stainless-steel gravity drain pan
🔹 Dampers: Two new plenum dampers + gravity backdraft dampers

Outcome

The completed project replaced the existing AHU with a new 16,000 CFM double-wall air handling system built around four direct-drive EC blowers and completely renewed filtration, heating, and cooling sections.

The new configuration consolidates the major air-handling components into one coordinated system designed for the existing mechanical infrastructure and the required 6.0 in. ESP operating condition.

The project demonstrates the difference between a component-level retrofit and a complete AHU replacement, where airflow, filtration, heating, cooling, fan configuration, duct connections, piping, and field installation must be treated as one integrated system.

For a broader framework on when an aging air handler should be repaired, retrofitted, or fully replaced, see our guide to repairing, retrofitting, or replacing a commercial AHU.

GRR Cooling Experts. Precision HVAC Retrofit Engineering for Critical Environments.

Request an HVAC Retrofit Review

If your facility is evaluating an aging AHU, complete air handling unit replacement, or modernization of multiple AHU sections, GRR Cooling Experts can review the existing conditions and help define a practical replacement approach.