I was on a trip passing through Delaware, the first state, when I noticed this cooling tower installed at grade level. It looked strangely out of place, so I took a closer look. Now, Whitney Houston said, and most would agree “I believe that children are our future.” However, the installation of this cooling tower may not support that statement. It has been installed at grade level adjacent to a children’s playground.
Before we go into why this is not safe and could be dangerous to the health of children that use this playground, let’s look at how this HVAC equipment works.
Cooling towers dissipate and remove heat from water-cooled refrigeration and air conditioning systems, such as chillers. Basically, what this means is that when chilled water passes through the air conditioning unit in the space being cooled, called the evaporator, directly or indirectly, it picks up the heat from the space. This water which has now increased in temperature needs to be taken outside so it can lose this absorbed heat, and reduce its temperature back to where it can be used again. It’s all a cycle.
This is where the cooling tower comes in. The cooling tower takes this “hot” water from the condenser side of the refrigeration cycle, and exposes it to a very large area that comes in contact with the atmosphere. This process can be done with spray nozzles for the water, and fans move atmospheric air through the spraying water.
When this happens, some of the water coming in contact with the air uses some of the previously absorbed heat energy, to change state from liquid to vapor. This leaves the water cooler and the air warmer. The heat that is exchanged and used to bring about this change of state is called the heat of vaporization.
Okay, so what does this have to do with the safety and wellbeing of those children? Well, the water vapor produced and atomized water from the spray is released into the ambient air surrounding the cooling tower, and it usually has the ideal temperature range for Legionnaires disease bacteria growth, 20°-50°C (68°-122°F). Also a small pool of water collects at the bottom of the cooling tower, that’s ideal for bacterial growth. And, air blowing over this pool of water adds to the water vapor being released.
Below is a schematic picture of this type of cooling tower, called a blow through type.
Cooling towers dissipate and remove heat from water-cooled refrigeration and air conditioning systems, such as chillers. Basically, what this means is that when chilled water passes through the air conditioning unit in the space being cooled, called the evaporator, directly or indirectly, it picks up the heat from the space. This water which has now increased in temperature needs to be taken outside so it can lose this absorbed heat, and reduce its temperature back to where it can be used again. It’s all a cycle.
This is where the cooling tower comes in. The cooling tower takes this “hot” water from the condenser side of the refrigeration cycle, and exposes it to a very large area that comes in contact with the atmosphere. This process can be done with spray nozzles for the water, and fans move atmospheric air through the spraying water.
When this happens, some of the water coming in contact with the air uses some of the previously absorbed heat energy, to change state from liquid to vapor. This leaves the water cooler and the air warmer. The heat that is exchanged and used to bring about this change of state is called the heat of vaporization.
Okay, so what does this have to do with the safety and wellbeing of those children? Well, the water vapor produced and atomized water from the spray is released into the ambient air surrounding the cooling tower, and it usually has the ideal temperature range for Legionnaires disease bacteria growth, 20°-50°C (68°-122°F). Also a small pool of water collects at the bottom of the cooling tower, that’s ideal for bacterial growth. And, air blowing over this pool of water adds to the water vapor being released.
Below is a schematic picture of this type of cooling tower, called a blow through type.
Lastly, the water passing through the cooling tower is chemically treated. And, you guessed it. Those chemicals also get released into the atmosphere.
So what is Legionnaires disease? The Mayo Clinic have the best definition:
So what is Legionnaires disease? The Mayo Clinic have the best definition:
And a little history from Wikipedia:
Legionnaires' disease is a severe form of pneumonia — lung inflammation usually caused by infection. Legionnaires' disease is caused by a bacterium known as legionella. Most people get Legionnaires' disease from inhaling the bacteria. The legionella bacterium also causes Pontiac fever, a milder illness resembling the flu. Separately or together, the two illnesses are sometimes called legionellosis. Pontiac fever usually clears on its own, but untreated Legionnaires' disease can be fatal.
Legionnaires' disease acquired its name in July 1976, when an outbreak of pneumonia occurred among people attending a convention of the American Legion at the Bellevue-Stratford Hotel in Philadelphia. Of the 182 reported cases, mostly men, 29 died.[19] On January 18, 1977, the causative agent was identified as a previously unknown strain of bacteria, subsequently named Legionella, and the species that caused the outbreak was named Legionella pneumophila.
Good maintenance is necessary, both to control the growth of the Legionnaire’s bacteria and for effective operation of the cooling tower. However, no offense to custodial staff and building maintenance crews, but engineers do not design based on the reliability and competence of the building staff. It’s the engineer’s responsibility to ensure system designed work nominally, without the active participation of third parties.
This is the main reason cooling towers are installed well above grade, and away from the fresh air intakes of building systems, including that of the adjacent buildings.
In general, factors in locating cooling towers are as follows (1) structural support requirements, (2) installation accessibility (3) local codes and ordinances, (4) cost of bringing auxiliary services to the cooling tower, and (5) architectural compatibility.
The first item that guides the engineer’s decision of where to place the cooling tower, safely, is item #3.
So what does the building code have to say?
Based on the location in Delaware of this cooling tower, the 2012 International Code Council Building Codes will govern its installation.
This is the main reason cooling towers are installed well above grade, and away from the fresh air intakes of building systems, including that of the adjacent buildings.
In general, factors in locating cooling towers are as follows (1) structural support requirements, (2) installation accessibility (3) local codes and ordinances, (4) cost of bringing auxiliary services to the cooling tower, and (5) architectural compatibility.
The first item that guides the engineer’s decision of where to place the cooling tower, safely, is item #3.
So what does the building code have to say?
Based on the location in Delaware of this cooling tower, the 2012 International Code Council Building Codes will govern its installation.
908.3 Location. Cooling towers, evaporative condensers and fluid coolers shall be located to prevent the discharge vapor plumes from entering occupied spaces. Plume discharges shall be not less than 5 feet above or 20 feet away from any ventilation inlet to a building. Location on the property shall be as required for buildings in accordance with the International Building Code.
So it’s not immediately clear, from the code, how to treat the cooling tower if it is installed on grade within the property lot line. It requires digging much further into the general section of the International Building Code, to figure out that last cryptic line “Location on the property shall be as required for buildings in accordance with the International Building Code (IBC).” The above section is from the Mechanical Code section of the IBC.
Not casting aspersions at the design engineer here, but since the code was not clear on what to do when the cooling tower is installed outside or near the property lot line, it seems they simple went ahead and placed it there. Afterall, it does not appear to be against the code. Even if it was flagged by the building official of the Authority Having Jurisdiction (AHJ), they can’t really say it is against the code. To be fair, the playground could have been installed after the installation of the cooling tower. And, the architect who designed the playground can't be expected to know the intricacies of a cooling tower, to know not to install a playground there.
New York City is known to have one of the most stringent and comprehensive building codes in the country (outside California – arguably). The 2008 New York City Building Code, is also based on the IBC, except it is amended by the New York City Building Department. So let’s look at what the New York City Building Code says.
Not casting aspersions at the design engineer here, but since the code was not clear on what to do when the cooling tower is installed outside or near the property lot line, it seems they simple went ahead and placed it there. Afterall, it does not appear to be against the code. Even if it was flagged by the building official of the Authority Having Jurisdiction (AHJ), they can’t really say it is against the code. To be fair, the playground could have been installed after the installation of the cooling tower. And, the architect who designed the playground can't be expected to know the intricacies of a cooling tower, to know not to install a playground there.
New York City is known to have one of the most stringent and comprehensive building codes in the country (outside California – arguably). The 2008 New York City Building Code, is also based on the IBC, except it is amended by the New York City Building Department. So let’s look at what the New York City Building Code says.
908.3.2 Outside. Cooling towers shall be constructed of noncombustible materials. Exception: Fill and drift eliminators may be made of limited combustibility materials provided all the following conditions are met: 1. The cooling tower is located on a building in construction group 1-A or 1-B of the New York City Building Code. 2. The cooling tower, fill and drift eliminators are located at least 30 feet (9144 mm) away from windows or fresh air intakes which are at an elevation above the roof on which the cooling tower is located, whether in the same building or in an adjoining building. 3. The cooling tower is located not less than 15 feet (4572 mm) from the lot line.
So, clearly the code officials in New York City caught this oversight in the IBC and amended it as required, so that the cooling tower cannot be installed less than 15’ from the lot line of the property. If this installation were in New York, it would be against the code and would have to be moved.
New York City moved unto the IBC codes in 2008. Before that, New York City had its own code, the 1968 New York City Building Code. This old code played a crucial role in ensuring the adoption of the IBC codes did not create lapses and gaps in stringency. So what did the 1968 building code say about the installation of cooling towers.
In the 1968 NYC building code, section 27-338 (i)(4)(c)
New York City moved unto the IBC codes in 2008. Before that, New York City had its own code, the 1968 New York City Building Code. This old code played a crucial role in ensuring the adoption of the IBC codes did not create lapses and gaps in stringency. So what did the 1968 building code say about the installation of cooling towers.
In the 1968 NYC building code, section 27-338 (i)(4)(c)
c. The cooling tower and filling and drift eliminators are located at least thirty feet away from any windows or fresh air intakes which are at an elevation above the roof on which the cooling tower is located, whether in the same building or in an adjoining building; d. The cooling tower is located not less than fifteen feet from the nearest lot line;
Therefore, the code officials in New York City had a precedence on which their amendment of the IBC are based. The officials in Delaware had no such luck.
So, "what about the children?"
So, "what about the children?"
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