Ventilation System Benefits – Required ventilation to keep product stable, remote monitoring, low noise, system expandable, desirable workplace environment, economical ventilation.
Systech was requested to develop a plant ventilation design which would both economically ventilate a facility with ambient outside air (mechanical cooling was not to be a consideration) while keeping introduced fan and make-up air (MUA) unit noise levels in the space at a maximum of 70 dBA. The area being ventilated includes both manufacturing and product storage with the product being stored having a low-temperature threshold for stability that must be kept at a consistent temperature throughout the year. The plant is in the northeast and the degree day design was 10 degrees F winter and 90 degrees F dry bulb summer. During the summer months, rooftop exhaust fans and make-up air (MUA) units worked together to provide six air-changes-per-hour (ACH) within the facility during production hours. Controls were implemented to turn down airflow during “off-hours” to conserve energy for the process and plant.
The system consists of four (4) rooftop exhaust fans that produce a maximum of 15,000 CFM each with 2 Horsepower PE motors (60,000 CFM total) and two (2) MUA units that produce 30,000 CFM each with 2,400,000 BTU heating and 20 HP PE motors.
The MUA units are 100 % outside air and during summer months are equipped with a summer/winter mode where natural gas heating is turned off and 100% outside air is supplied to the facility when temperatures reach 65 degrees F.
Each fan inlet and MUA unit outlet is equipped with a silencer to reduce the noise levels to meet the 70-dBA space requirement when all equipment is running. Keeping in mind when running four (4) fans simultaneously, with each having the same noise level, an increasing multiplication factor is applied, and the silencers must be designed to attenuate below the 70-dBA final room design noise level.
All fans are controlled with Variable Frequency Drives (VFD) using premium efficiency motors and line reactors for motor and VFD protection, to adjust the range of performance to meet the client’s temperature requirement. SysTech supplied the electrical control package including VFDs, line reactors and components as part of the electrical portion of the project, along with a PLC based control system to continuously monitor the status of each fan and both MUA units. Gauges indicate equipment status of “on” or “off” mode and their respective airflow. This design allows the system components to be viewed and controlled (on/off) from the plant offices or remotely from outside the plant area. It displays amperage and frequency to allow this to be converted to actual CFM. Remote monitoring was an important benefit to the client who had experienced issues where rooftop ventilation equipment wasn’t running or where they were running fans without belts or eroded fan blades (motors only). Remote monitoring is ideal for those zero-degree or 100-degree days when no one goes to the roof to inspect why equipment is not heating or fresh air is not exhausting out of the plant. Equipment functionality can be monitored from a 70-degree F temperature-controlled office space and a “fix-in-place” takes a lot less time for maintenance to diagnose and correct.
The control system is expandable should future changes occur in ventilation requirements for the facility. The ventilation design, if required, can be changed down the line should the client need new and/or existing ventilation components monitored or added by simple modifications to the PLC system. The expandable nature of the PLC allows for endless options to the site.
At the project’s completion, Systech took noise measurements in the storage and production areas and values were lower than the 70-dBA system design parameters, between 65-67 dBA creating a desirable workplace environment.