A local hotel approached Climate Control Systems and Service to investigate an atrium that is approximately 11,950 square feet. The space is 8 stories tall and is served by 4 roof mounted air handling units. All airflow was supplied and returned at the ceiling with temperature sensors at various floors. The Client indicated that the space never seemed to heat or cool properly since they had taken ownership. They had been receiving thermal comfort complaints from their patrons and noted that when the front doors opened large volumes of air from outside would come rushing in. Finally, the client indicated that they could smell the chlorine from the adjacent pool room.
Assessment
Upon our initial survey we noted that the building automation had been dismantled and there was not control on the heating and cooling mode of the 4 air-handling units. The dampers that allow outside air into the space had also been dismantled. We had also determined that the space was stratified, our preliminary investigation determined that the top floor was 18 degrees hotter than the ground level. Neither the upper floor nor the ground levels could meet standards for thermal comfort.
Proposal
Climate Control Systems & Service recommended:
- Replace the automation on the 4 roof top units to include
- Restore the heating and cooling operation.
- Restore the outside air damper operation and modulate for building pressure
- Provide low temperature lockouts
- Provide supply, return, and mixed air temperature monitoring
- Provide fan status sensors
- Replace temperature sensors
- Provide space destratification fans
- Fans modulate (speed up/ slow down) as required to maintain uniform temperature from floor to ceiling
Results
Results/Temperature Controls:
- The air no longer was rushing through open doors
- The chlorine smell dissipated
- Less than ½ degree temperature difference between the top floor and ground level
Results/Destratification:
- Thermal comfort was restored
At startup of destratification fans the temperature difference between the ground level was 18 degrees. Less than 5 minutes after startup it was reduced to ½ degree difference. - Reduced energy consumption
This was accomplished by providing a uniform temperature between the upper and lower levels. The roof mounted air-handlers do not have to “stack up” the heat to satisfy the lower level thermostat. With the controls restored on the air handling units, the upper level thermostat would call for cooling while the lower level thermostat was calling for heating.
Conclusion
Client reports that the space is much more comfortable. The Return On Investment (ROI) for destratification fans is 3.25 years.
