#Sf of louver per cfm airflow calculator free#

Once airflow is known and a louver is selected, the following formula calculates the louver area required for ventilation. Finally, when using outside air to ventilate a plant, filtration is often desired to maintain clean equipment.

#Sf of louver per cfm airflow calculator free#

It’s common for louvers to have 50 % to 60% free area, requiring the desired louver size to maintain a maximum air velocity to be close to twice the size of the hole. The construction of louvers also result s in a dramatic reduction of available free area compared to the size of the hole it fills.

When reviewing louvers, manufacturers publish a maximum air velocity (f ee t/min ute ) of the airflow to avoid carry-over. When exhausting large amounts of air, there must be a louvered opening in the plant large enough to both allow the maximum required cubic feet per minute through and also not have water carry over during a rain event. Even with the proper amount of ventilation air, if the air doesn’t move through the space appropriately the desired space temperatures will not be achieved throughout the plant. As the heat is generated by specific sources in the chiller plant, it’s critical to e nsure the air pathways don’t leave “dead zones” with little air movement. The common calculation to determine ventilation airflow required isĪSHRAE 15 : Safety Standards for Refrigeration Systems, Chapter 8.11 states that a machinery room shall not have less than 0.5 cfm/ square feet or 20 cfm per person while occupied and also sets a maximum temperature rise of 18☏.Ĭonsiderations to take into account when using a ventilation approach are airflow paths and intake air space.

When ventilating a plant, both the climate and desired plant temperatures must be taken into account. The decision should be made between the two before designing the system to manage heat. There are two main ways to manage heat in a chiller plant, ventilation and mechanical cooling. Courtesy: Jonathan Eveleth, RMF Engineering This table shows the theoretical heat load in a 2,000-ton chiller plant. Table 1: Heat loads: 2,000-ton chiller plant As you can see, the impact of an open-drive chiller and an air-cooled chiller VFD have a significant impact on the room’s sensible heat load. See Table 1 for an example of a fully variable speed chiller plant load chart.

Small miscellaneous loads : Space lighting, uninsulated condenser water piping, electrical gear, uninterruptible power supply backups, control systems, etc.

Envelope loads : D ependent on space temperature requirements and geographic location.

Harmonic control devices : If the electrical system can’t handle the harmonics associated with VFDs, harmonic control devices introduce efficiency losses and associated waste heat.

Transformers : While typically located outside, these can add significant heat load if located in the chiller plant.

In addition to mechanical equipment, the following should be considered when calculating heat load: The DOE publishes values representative of a “typical” VFD.

Similar to motors, every VFD manufacturer publishes its own efficiency data on their products. When dealing with medium voltage machines (4, 160 volts and higher) the VFD waste heat is regularly discharged to the space. Ĭhiller VFDs are often water cooled on a 480 volts or lesser voltage machine and do not reject waste heat to the space. Most stand-alone VFDs (pump and tower motors) are air – cooled and reject waste heat to the space. While these drives allow for an overall more efficient system, they do introduce inefficiency in the conversion of the power from 60 hertz to a lower frequency. Many chillers and pumps us e variable frequency drives for greater efficiency at part-load conditions. For motors of more than 10 horsepower, minimum standards exceed 90% efficiency with larger motors (200 horsepower and above) around 95% efficient. The DOE publishes a guide for motor selection and application. Department of Energy shows the adoption status for each state. ASHRAE 90.1 : Energy Standard for Buildings Except Low-Rise Residential Buildings dictates minimum efficiency standards for electrical motors us ed in commercial settings. In addition to chiller motors, any additional smaller motors in the room must be taken into account when considering heat losses.