Beating the summer heat

Using large-diameter, low-speed fans to make your plant more comfortable

June 26, 2012

Summertime and the factory is even hotter. Here’s a look at one option for making conditions more tolerable and safer for your workforce.

With all their heat-producing machinery and processes, manufacturing facilities can be very hot, uncomfortable, and unsafe workplaces. This can be especially true in the summer months. Studies have shown that improved occupant comfort leads to increased productivity and that worker productivity decreases as temperatures rise above 77 degrees F.¹

A comfortable environment also improves employee retention, which is a critical factor in an industry that’s struggling to find workers.

The following FAQs provide answers about improving your operation’s comfort using large-diameter, low-speed fans.

1. When it comes to working indoors during the summer, what are the optimal environmental conditions to ensure employee comfort and expected levels of productivity? How can that type of environment be maintained as summer temperatures escalate?

Feeling comfortable depends on more than just air temperature. Human thermal comfort takes into account numerous environmental factors, including temperature, thermal radiation, humidity, and air speed as defined by ASHRAE Standard 55-2010 (American Society of Heating, Refrigerating, and Air-conditioning Engineers), along with personal factors such as activity level and clothing.

When the temperature and humidity rise, the body’s ability to cool itself decreases. Reducing the amount of clothing worn is greatly valued, and incorporating natural ventilation where applicable can help. Granted, in the manufacturing industry, reducing activity level generally is not an option, and many jobs require protective clothing. However, applying gentle, nondisruptive, nonturbulent airflow from large-diameter, low-speed fans can aid the evaporative cooling process and help to maintain employee comfort even in hot conditions. 

2. How do fans help address uncomfortable humidity levels?

Large-diameter, low-speed fans do not increase or reduce the amount of humidity in the space, nor will they change the temperature of the air. The airflow provides a cooling effect on occupants, similar to a natural breeze. Additionally, a fan can distribute or even out any humidity or temperature discrepancies so the vertical and horizontal temperature and humidity levels are the same. Achieving this effect requires the right number of properly sized fans, appropriately placed. 

3. What’s the best way to maintain a comfortable working environment in a large workspace, such as a 10,000-sq.-ft. shop floor? Alternatively, what’s the best approach to maintaining suitable work conditions in a confined area, such as a welding cell?

Given the number of factors involved in laying out an effective system for occupant comfort, this question is not easily answered without adequate information about the climate, type of conditioning if any, obstructions in the space, amount of process heat involved, and the presence of  natural ventilation, to suggest a few. Fan manufacturers have trained experts who can help determine a space’s specific needs.

4. How do I get an idea of what sort of cooling system makes sense for my facility?

Numerous factors are involved in choosing an appropriate cooling system for a specific location. One factor is no more or less important than others, and you must weigh all of them.

• Building envelope – A poorly insulated building requires more air conditioning, which is expensive to purchase and install.
• Occupant density – Does it make sense to air condition a 30,000-sq.-ft. building with five occupants?
• Local climate – Consider San Francisco vs. Death Valley; what’s appropriate for my climate?
• Local utility costs –Electricity is a lot more expensive in some parts of the country than others.
• Activity level – Will workers be mobile or stationary?
• Budget – Upfront costs vs. long-term costs. The right kind of system has to be affordable to install and operate, plus provide sufficient comfort for the building’s occupants.

5. What can be done to minimize the noise generated by large fans?

Unlike small, high-speed fans that generate upward of 85 dBA, properly engineered industrial large-diameter, low-speed fans typically create sound levels of less than 55 dBA—the quiet end of the range for household dishwashers.

However, a fan’s decibel level does not tell the entire story.  Clearly distinguishable tones (single frequencies) can cause a sound to seem louder than its actual dBA, thus causing significant annoyance even at theoretically acceptable dBA levels.  Once a tonal noise has been heard, it is more easily recognized, even at lower sound levels. In other words, both sound quantity and sound quality should be considered before a fan is installed to prevent occupant noise complaints.

In addition to the high-pitched electrical noise sometimes caused by placing the fan’s variable frequency drive far from its motor, gear reducers and bearings can create tonal noises in the 400 to 2,000 Hz range that are problematic in sound-sensitive areas.  While not as unpleasant as electrical noise, mechanical tonal noise can still be a significant source of occupant complaints. For sound-sensitive applications, it is recommended that fans with high-quality bearings and direct-drive motors (without gears) be used. 

6. How much energy is needed to run fans? What sort of an impact will it make on my company’s utility bill?

Energy usage depends on the size and number of fans, horsepower of the motors, hours of operation per week, and the local cost of electricity. With typical hours of operation during the summer months, a 12- to 24-ft. large-diameter, low-speed fan uses, on average, 7.1 to 11.6 kWh of energy on a daily basis, which is less than an air-conditioning system and more applicable in most warehouse facilities.

1. O Seppanen, WJ Fisk, and D. Faulkner, “Cost benefits analysis of the night-time ventilative cooling,” in proceedings from Healthy Buildings 2003 Conference, Singapore, 2003.

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