ACHRNEWS

Proof That Rooftop Solutions Feature Flexibility

September 11, 2002
Fossils's new distribution facility includes 51 Lennox L Series rooftop units totaling 1,055 tons, as well as 15 tons of 16 Series rooftop units and 29 Series split systems atop the roof, for a total of 1,070 tons of HVAC equipment.
GARLAND, TX — Cooling a building the size of 17 football fields (approximately 517,500 square feet) calls for a “flexible” solution, especially when it contains a warehouse, office space, a data center, and a 400-person capacity meeting room. This new facility in Garland is the hub for Fossil’s merchandise shipment and repairs. The company makes watches, clocks, eyewear, and accessories.

Fossil building staff reviewed the varying cooling needs of the different environments in their new distribution center. Lennox equipment was chosen.

Chris Murray, Lennox commercial territory manager for the Dallas area, worked with Venture Mechanical, a design-build contractor, to complete the job. “We have a strong relationship with Venture Mechanical,” said Murray.

The distribution facility houses the office space in the front and back of the warehouse, with the warehouse in the middle. L Series® rooftop units are used for the warehouse, L Series rooftop units and 16 Series™ rooftop units are used for the office space, and HS/HP29 split systems are used for the data center.

Venture installed 36 25-ton L Series units to cool the warehouse to a target temperature of approximately 80 degrees F. When the job was completed, the Fossil distribution facility had 51 L Series rooftop units totaling 1,055 tons; and 15 tons of 16 Series rooftop units and 29 Series split systems atop the roof, for a total of 1,070 tons of HVAC equipment.

The units were wired to Honeywell XL direct digital controllers inside the building at the client’s request.

Sonny's Real Pit Bar-B-Q franchised barbecue restaurants are roughly 5,600 square feet with a main dining area seating roughly 200 people at maximum capacity, and a kitchen. Typically, three 12-ton L Series rooftop units are used at each restaurant.

A FLEXIBLE SOLUTION

Jeff Rushing, vice president of Venture Mechanical, stated, “Our 14- to 15-year relationship with them [Lennox] has shown that they build a good product and deliver it well. We get more BTUs — more cooling capacity — with fewer rooftop units used.”

He added that “The 25-ton L Series rooftop unit is a great bargain for the cost per ton. It’s friendly on the service side. The configure-to-order features include angled coils to prevent hail damage, and safety features include factory-mounted smoke detectors and economizers. We also requested demand-control ventilation with CO2 sensors for the meeting rooms, so the units created a suitable climate for the appropriate number of people.”

The 16 Series rooftop units were used for the office space, where fewer tons were needed. The HS/HP29 rooftop split systems were used in the data center for cooling only.

“We were very pleased with [the] equipment and our trouble-free installation, since it was such a huge job,” said Jason Stewart, engineer and product manager for Venture Mechanical. “I wish we had more projects of this caliber.”

L Series commercial packaged rooftop units from Lennox have efficiency ratings of 12.0 EER and 13.4 IPLV.

RESTAURANT APPLICATION

Contractor Charles Berg chose Lennox equipment for the HVAC needs of Sonny’s Real Pit Bar-B-Q franchised barbecue restaurants. The choice was important, because good food is only part of the dining experience; a pleasant atmosphere adds to (or detracts from) the ambience. The comfort of the restaurant patrons and the indoor air quality of the building are key considerations.

The contractor supplies most of the HVAC services for the Sonny’s restaurants in the Southeast. They assist with both new construction and retrofit/replacement jobs.

“We get a lot of job orders for Sonny’s restaurants,” said Berg, president and owner of Charles Berg Enterprises, Gainesville, FL. “Some of these restaurants are owned by Sonny’s, while others are owned by franchisers. Each client decides what type of HVAC system to use.”

Each Sonny’s restaurant is roughly 5,600 square feet with a main dining area seating roughly 200 people at maximum capacity, and a kitchen. Three 12-ton L Series® rooftop units are used at each restaurant.

Each rooftop unit is configured to order with factory-installed smoke detectors and motorized outside air dampers. CO2 sensors in the dining room allow the climate system to account for the actual number of people in the room, and call to bring in enough fresh outside air to keep the climate and humidity stable.

By meeting the restaurant’s fresh air ventilation requirements based on actual occupancy, rather than its maximum design occupancy, the restaurant saves cooling costs and increases efficiency, according to Lennox.

NETWORK CONTROL

Many of the Sonny’s restaurants use the Network Control Panel (NCP) network manager to control their HVAC systems. Developed by Lennox, this device allows the operator to control the temperature and humidity, program different schedules, and quickly make changes.

An additional software package allows the operator to set up and monitor the NCP from a computer at a remote location.

“Our clients who use the Network Control Panel realize how easy it is to use,” said Kevin LaCoste, project manager at Charles Berg.

“Some franchise owners have as many as 18 stores. The possibility of controlling all 18 NCP panels from one central computer with the NCP software package is very appealing to them.”

The rooftop equipment networked with the NCP and modem package allows remote access to monitor real-time conditions and date-stamped alarms — a good thing, because some stores are five hours from the contractor’s office.

“Knowing the alarms and current conditions via remote monitoring is a huge time saver for us,” said LaCoste.

“We can also schedule other services for stores on the same route as the store needing service, which makes the technician’s time more productive.”

INNOVATIVE PROBLEM SOLVING

In many restaurant environments, internal building pressure directly affects the heating-cooling system. Exhaust air can quickly build from cooking and grilling. The HVAC systems in Sonny’s restaurants are designed to bring in fresh air over the grill area through compensating-type hoods. The exhaust and makeup air fans can maintain a 200-CFM positive building pressure.

If there is too little fresh air, unconditioned air will be drawn from ceilings, doors, and windows. If there is too much fresh air, smoke can be pushed into the dining area. Too much fresh air can also cause humid air to get sucked into the building, and it can’t be dried quickly. To ensure proper pressure, the outside air dampers must open the right amount — but worn belts or fans on the air conditioner can affect the amount of incoming fresh air through the dampers.

To meet these challenges, LaCoste implemented one of his own designs in several new construction jobs, using the NCP and L Series rooftop units. He installed a pressure transducer in the air conditioned kitchen, and wired it to the Integrated Modular Control (IMC) unit controller in the L Series. The IMC is set up to modulate fresh air when connected to a CO2 sensor.

The CO2 sensor and the pressure transducer both have a 0- to 10-V output signal. Using the input for the CO2 sensor, the contractor can modulate the outdoor air using the pressure transducer.

MAINTENANCE

By adding the pressure transducer, the kitchen unit is able to compensate for worn belts, dirty filters, or additional exhaust fans. Normally, worn parts cause decreased airflow from outside and can throw the building into positive or negative pressure. Using the transducer ensures that the worn parts will not automatically cause the building to assume negative pressure from decreased outside airflow.

“We use Lennox equipment mainly for the ease of maintenance,” said Berg. “Managers can even walk up to the L Series rooftop unit, turn the handle to open the door, and change the filters.”

“The IMC unit controller also makes maintenance easier, since we wired the pressure transducer to it so we can monitor it through the NCP,” said LaCoste. “Instead of looking at the actual fans and belts to see if they’re worn, we can simply look at the NCP to find out how much the outside air dampers are open. If the air dampers are open more than in the past, that’s a good indication that the belts and filters may need maintenance or replacement.”

Before the retrofits, Sonny’s wall-to-wall wood paneling in the dining areas had been turning black with mold from increased humidity. When Berg was called in to retrofit the existing restaurants’ HVAC systems, Sonny’s owners found the new systems helped decrease the mold problem, saving thousands of dollars normally used for replacing the paneling.

Publication date: 09/16/2002