SAN ANTONIO, TX — Nearly three million people a year flock to the Alamo, a 4.2-acre stone-walled complex where a small, fierce band of Texans, including Davy Crockett and William B. Travis, tried to repel a 13-day assault by General Antonio Lopez de Santa Anna.

However, this piece of historical Americana doesn’t operate by itself. It takes 90 workers to administer the functions that keep the 300-year-old park open to the public and maintain its pristine condition.

Nearly one-third of the staff works in an outer building known as the Support Center, located at the rear of the grounds.

When it came time to renew the center’s ailing, CFC-charged cooling and gas-fired heating system, a local consulting engineer with Texas ancestry going back to the 1700s, James T. Rodriguez, was selected to specify the hvac system as part of a retrofit of the historic site.

He and the rest of the Alamo’s team of consulting engineers and contractors decided to replace the 20-year-old, 4-ton split system, intended primarily for residential applications, with a 7.5-ton, gas-electric rooftop unit (manufactured by York Internation-al’s Unitary Products Group).

Adios, old system

The Support Center’s previous hvac equipment, like most of the facility’s mechanical systems, was designed for residential use, and as such was not properly sized.

Plus, it was nearing the end of its useful lifecycle. The 20-year old unit could no longer keep pace with the center’s expanding floor plan, according to James Butler, president of Southwest Mechanical Service, the installing contractor.

“I was contacted to investigate the inadequacies of the existing system,” said engineer Rodriguez. “The unit was not cooling as well as they wanted it to, which was complicated by the fact that the director’s office was reconfigured into office spaces for three people.”

Rodriguez concluded that a self-contained rooftop unit was a more viable replacement option than a split-system heat pump.

The engineer recommended a 7.5-ton gas-electric packaged rooftop unit, which was installed in August 1998 by contractor Southwest Mechanical.

Hola, new unit

The unit has an electric energy efficiency rating (EER) of 9.0, with an 80% annual fuel utilization efficiency (AFUE) rating.

Using the engineer’s drawings, Southwest Mechanical installed the equipment, made ductwork modifications, and performed the post-installation commissioning.

The unit was placed on a cement slab in a parking lot at the rear of the building. The decision to locate the rooftop unit on the ground was based mainly on aesthetic factors, in addition to the need to minimize the overall visual impact of mechanical systems at the site.

Putting the rooftop unit on the ground also alleviated utility service-connection and air-distribution issues that would normally have been associated with a split system.

“The Alamo’s administrators didn’t want a rooftop-mounted unit because it would have been in full view of the general public,” said contractor Butler.

“It’s been running fine since we installed it and we haven’t had a callback since.”

Transitions: split to packaged airflow

Ductwork modifications were needed to accommodate the new system’s location and to make the transition from split- to packaged-system airflow.

The contractor removed an existing indoor blower from a closet in the director’s office to make way for a new duct chase in the center’s sidewall. The ducts also were painted to match the building’s exterior.

This particular comfort-conditioning enhancement is part of an ongoing effort to evaluate and upgrade all of the memorial’s hvac systems.

For Rodriguez, a San Antonio native with a long ancestry in the area, the retrofit had special meaning.

“Being a part of the Alamo’s comfort improvement projects has been greatly rewarding from both a historical and a personal standpoint,” he said.

Sidebar: Comfort control deep in the heart of Texas

Located in downtown San Antonio, the Alamo’s Shrine, Long Barrack Museum and Gift Museum house feature exhibits on the Texas Revolution and Texas history. It’s open year round in a climate where a good portion of that year is unquestionably hot.

The Support Center and its climate control systems play a vital role in the Alamo’s administration, managed since 1905 by the Daughters of the Republic of Texas.

“The center’s hvac system keeps about 30% of the Alamo staff in a climate-controlled environment and maintains their productivity,” stated Bradford R. Breuer, the Alamo’s director.

The single-story building occupies 3,000 sq ft, including public restrooms, the director’s office, a receptionist’s office, the security department, and a maintenance office.