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Right-sizing HVAC Works Wonders

Right-sizing HVAC Works Wonders

Most contractors will point to technical issues when asked to recall the most challenging aspects of a residential HVAC installation. But for Tim Bruce, owner/founder, General Air Conditioning, San Antonio, TX, the highest hurdle he and his team had to clear was one of perception: convincing the homeowners that their old system — a pair of 10-SEER units — was just too darn big.

They did agree that it was old and inefficient, and that something had to take its place. This two-story, four bedroom home was being heated and cooled by two 10-SEER, gas furnace split systems installed in 1996. Five tons were cooling the 1,800 sq. ft. lower level, while another three tons conditioned air on the 900 sq. ft. upper level, which includes a guest room, music room, and two children’s bedrooms.

“Other contractors had only provided prices on replacing the existing system with like-size equipment,” Bruce says. “We were able to show them how one system would save money up front on the installation, and how proper insulation and testing would save money on operating costs. Only having one system to maintain was another valuable savings feature we recommended.”

The homeowners — Mr. and Mrs. Scott Kirk —wanted to reduce their overall energy consumption and maintain comfort throughout the home, and improve the home’s defense of outdoor allergens, notably oak and cedar tree pollen.

Of particular concern from a temperature standpoint was a quest for comfort in the west-facing master bedroom, and in the guest room directly above it, in late afternoons. The Kirks also wanted daily comfort in the loft and music room, so their children could practice their musical instruments in clean, cool air.

A challenging structural feature of the home had always been that the loft was open to the living room. Consequently, air from the upstairs system affected the thermostat located in that space, leaving the lower level master bedroom and guest room at uncomfortable temperatures. Therefore, the General Air Conditioning Team faced a three-fold challenge:

  • reduce energy drain
  • equalize room temperatures
  • clean the air.

With these goals in mind, the team got down to work.

Eight Take Away Three = Correct Comfort
A load calculation was performed, which showed the home really needed a bit over five tons of cooling at any given time, rather than the eight-tons that had been previously installed. An air delivery test was performed on both systems using Escan test equipment by Enalasys. Massive air leaks were detected in the upper and lower duct systems, as well as undersized return ducts.

This is where General Air differentiated itself from competitors. For six months prior to the project, the Kirks had received several estimates from area contractors, but General Air was the only team to perform a load calculation and air delivery test on the home and system.

General Air got the job, albeit with a tough project window: complete it between Christmas and New Year’s Day, to accommodate Mr. Kirk’s schedule as an airline pilot, and to work around the contractor installing radiant barrier in the home’s attic.

Once they were “cleared for takeoff,” the three-person General Air team removed the old equipment from the attic — to make room for the radiant barrier installation — and began work on removing the old outdoor unit.

After the radiant barrier contractor had provided for the home’s insulation needs, General Air installed the furnace, zone dampers, controls, and necessary ductwork. They required every minute of their project window, and took the work right up to New Year’s Eve day. To make the most of their time, they worked as a team to keep the home clean during the week long installation.

They were good communicators, too, Bruce says. “They kept the homeowners informed, and offered suggestions about thermostat locations, or how adding a grille to the home’s entertainment closet, would serve to better exhaust excess heat generated by the electronics system,” he recalls.

Following the installation, a test-out of the home’s air delivery system was performed, to verify room-to-room performance, and overall duct leakage.

“The ductwork that feeds the lower level was all concealed between the floors, so there were some issues that just couldn’t be overcome without extensive home remodeling,” Bruce explains.

Useful Controllers Serve a Comfort Purpose
As a pilot, and someone interested in the capabilities and benefits of modern comfort technology, Mr. Kirk wanted a system with a remote control. He was given detailed instruction on the use of the Trane TZONE950 controller, and being comfortable with high-level controls, he was able to set up the wireless network to enable remote control of his system, and to receive local weather right at the controller. The controller was also set to log run times so that at the end of the year, both the customer and contractor could review how much any zone or any stage of the equipment was being used. The entire range of installed equipment received a Trane 10-year parts and labor extended warranty. General Air Conditioning matched the warranty on its workmanship for non-covered items, and provide a one-year, two-visit maintenance agreement, known as the 4-Star Maintenance Agreement.

The Proof is in the Comfort
Tim Bruce says this project proves that a bigger comfort system isn’t necessarily the best choice for a customer.

“We removed three tons of air, reducing the system by about 40%. Now, we have evidence that the smaller system was the better choice,” Bruce says.

“The Kirks believed in us to give them what they wanted: constant, even temperatures, efficiency, and the ability to control four areas of the house evenly,” Bruce says. “That’s often a concern for people with larger homes. There’s always one unit controlling a larger area, and one guest room or alcove that isn’t satisfied as well as the rest of the home.”

This project also proves the value of providing an exact, professional assessment of the existing home HVAC system, as a foundation to building trust, right from the start.


  • Trane XL20i air conditioner
  • Trane XC80 variable speed gas furnace
  • Trane cooling coil
  • Trane CleanEffects
  • Trane TZONE 950 communicating comfort control
  • Trane TZONE zone panel
  • Attic-Tent
  • Johns-Manville coated duct board
  • Air Seal 33 Mastic
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