Task

National TAB Intelligence performed the Revive service on a national chain restaurant that was struggling with building pressure complaints. Revive is a service our team offers to perform commissioning and testing, adjusting, & balancing on an existing facility to discover and resolve the deficiencies causing the health, comfort and control problems experienced by the operators and customers.

The first thing our field technician did on site was meet with employees to gain a better understanding of the issues occurring in the restaurant. The largest complaint was how hard it was to open the front doors of the restaurant, which was caused by the building’s negative pressure. Additional complaints about the overall comfort of the space were noted by the technician.

Solution

Solving the “Effect”

Fixing the negative building pressure in the restaurant was the main objective. There were three significant fixes our technician made to resolve this.

First, the tech discovered that the rooftop unit serving the dining room was low on airflow, while the one serving the kitchen was providing an adequate amount. This caused localized areas of higher and lower pressure, impacting the air movement throughout the building and reduced the cooling and heating load management the units were designed to deliver. The technician corrected the airflow setup and balanced the diffusers to get the right amount of airflow out of both units.

Second, the outside air dampers were found completely shut on both units. This was the major contributing factor to the negative building pressure. These were set to the proper setpoint and balanced to the appropriate amount of ventilation airflow for both units.

Solving the “Cause”

While not part of resolving the building pressure, it was also noted that the humidity sensors for the kitchen RTU were not wired properly. This meant that the unit was never dehumidifying and, likely, the outside air dampers were shut to try to Band-Aid the humidity issue. Uncovering this underlying issue was key for maintaining the long-term building balance and performance.

Third, the technician found that the occupancy schedule for the thermostats was set up for store hours, but not when the store was occupied (when the employees first arrived to start cooking for the day). When the employees started turning on the kitchen hoods to cook, the outdoor air dampers were closed, creating a vacuum and not allowing outdoor air in to replace the exhausted air. This resulted in negative building pressure. In a restaurant like this one, it is best to be slightly positive during operational hours. The technician fixed this by changing the thermostat schedule to turn on when the store was occupied, defined by when operations began and ended.

Results

The customer noticed an immediate change in the comfortability after the NTi technician performed the Revive. The space was more comfortable, there was better airflow, and the doors were easier to open. The rooftop units serving this building are aging, but the technician was able to get them to a place they could handle the demand and improve comfortability without the client having to spend thousands of dollars on new equipment.

Have a sick building in need of assistance? Reach out to the NTi team to schedule a building Revive. Our team of field engineers take the time to uncover building issues and provide customers with actionable insights.