Richard Kirkland, Sales Manager for Business Development, at Mestex exhibited a display version of the Aztec indirect evaporative cooling system at the recent Texas Air Systems sponsored golf tournament for the DFW ASHRAE chapters.

The unit on display was the smallest of the Aztec indirect evaporative cooling line and included the features most in demand for the data center and server room market. DDC controls, VFD supply and cooling tower fans, direct drive plenum supply fan on vibration isolation, and fire resistant fiberglass cooling tower media were all part of the display unit.

One of the first lessons from the past is that hot air rises.  Seems obvious doesn't it?  Believe it or not there is actually a company that is successfully convincing people that by making their air even hotter than everyone else they can do a better job of keeping people comfortable from 20 or 30 feet above them.  But that is a different story for another time.

Because people realized that hot air rises, many early structures in very warm climates would be built with very high roof lines.  This would allow the hottest air to stay above the people and increase their comfort.  Many of those structures would also have vents or openings at the highest point of the roof so that the hot air could escape.  As that hot air left the structure it would be replaced by cooler outside air near the floor level.  A continuous circulation pattern would develop that kept the "cooling cycle" going.  The taller the structure, and the hotter the air, the faster this cycle would operate.  Today, we call that phenomenon "stack effect" and you see it in every tall building elevator shaft in the world.  You also see it in chimneys for residences.

After the invention of air conditioning though we seem to have forgotten one of the key elements of this natural cooling cycle...venting the hot air out of the building.  In most modern air conditioned buildings we keep the hottest air inside the building and just keep cooling it back down in a constant cycle that requires compressor or chiller energy.  In many cases the hot air inside the building is still cooler than the hot air outside the building so this might make sense during the hottest months of the year.  However, in the case of a data center or server room, the hot aisle air is usually much hotter than the air outside...but most data centers use cooling equipment that constantly tries to cool down that hot aisle air resulting in huge energy consumption.

Some systems also take advantage of the "stack effect" in a shorter building by recognizing that any heat source in the space will create it's own "mini stack effect".  Cooler air will be drawn towards the heat source and the hot air above the heat source can be exhausted.  This creates some natural circulation in the space and is one of the key principles behind "displacement ventilation".

Another lesson from the past is that evaporating water will make air cooler.  We actually use that very same principle in modern chiller systems that include a cooling tower.  The cooling tower is nothing more than a very large evaporative cooler.  In the old days people would use wet cloths or reeds in a window opening and when air entered the building through those wet items (probably accelerated by the building "stack effect") the entering air would get cooler and the people would be more comfortable.  Today there are many types and sizes of evaporative coolers available, such as those from Alton and Aztec divisions of Mestek, and they work even better than those primitive early methods.  But no compressor or chiller energy is required.

Of course there are building construction techniques that are also based on lessons from the past.  Positioning a building so that the smallest outside wall area is the one that sees the most sun will help keep the occupants cooler.  Using "thermal mass"...thick, heavy, walls...can also keep occupants cooler by storing cool night air energy in the wall and releasing it slowly during the hottest part of the day.  Again, we often build very light weight buildings today and try to compensate by adding insulation but nothing beats two feet of solid rock.  Some architects are working to revive this technique and research is continuing on using chemical treatments on walls and ceilings that allow them to store energy longer.  One case where creating a lot of "thermal mass" might not be such a good idea is in the data center world.  Depending upon how the hot aisle air is handled it might actually be a good idea to make the walls very thin so that the heat can escape to the outside through the walls.  Finally, the use of shades and window coverings is also a key lesson from the past.  Some companies, such as the American Warming division of Mestek, offer exterior solar shades that actually track the position of the sun and change angle in order to maximize the shading effect.

There are many other lessons from the past that could be discussed but the key is to stop and think about how we used to do things.  Sometimes adapting ideas from the past to ideas from today can result in the best overall solution.

Over the Christmas/New Years holiday break I was able to spend some time on the road crossing Texas, New Mexico, and parts of Arizona.  While I saw plenty of interesting sights it is not the goal of this blog to create a travel channel.  The goal is to highlight technologies and subjects of interest in the HVAC arena.

The subject that came to mind as I drove across these states was that of indoor air quality.  Two areas, in particular, raised my attention to this topic.  Phoenix, Arizona and El Paso, Texas were both covered with a thick layer of smog as I passed through those towns.  The climatic reasons are not all that relevant to this discussion but the "temperature inversions" that are common in those areas at certain times of the year mean that smog will develop and stay trapped for hours, if not days.  But those two cities are not alone.  Los Angeles, California has been well known for poor air quality for years.  New York City leaders have become concerned enough about outside air quality to include provisions in their new "Green Codes" that are intended to address the issue.  Finally, attention has been brought by the folks at NOAA to the fact that pollution in China eventually makes it way to the US on the jet stream.

HVAC products can either help mitigate this problem or simply move it from the outdoors to the indoors.  All buildings with occupants are required by building codes to have some amount of "ventilation air".  It has been common practice to introduce that ventilation air through conventional air handlers or packaged rooftop equipment.  In the vast majority of cases that equipment was designed, and is applied, with only the minimum level of air filtration included.  The primary goal of the filtration has been to protect the components of the equipment from dust fouling and to provide a nominal level of indoor air quality improvement.  New requirements and guidelines that specify MERV 11 and higher filtration are intended to let the equipment begin to mitigate the outdoor air quality before it enters the space.  But how effective is this?

In a conventional HVAC system design there will be dozens of these filters, if not hundreds, scattered all over the building in numerous air handlers or packaged units.  Maintaining all of these filters properly becomes an ongoing task.  In addition, if even better filtration is required, or desired, the average piece of HVAC equipment simply lacks the space to provide more filtration.

Dedicated Outdoor Air Systems, or "DOAS", equipment helps address this.  By isolating all of the ventilation air requirements into a single point, maintenance of the filtration system becomes much easier.  In addition, some "DOAS" equipment, such as the Applied Air FAP, is designed to allow multiple stages of filtration.  When combined with low airflow systems such as chilled beams the result can be very clean ventilation air even in areas such as those I drove through over the holidays.

As a final consideration for indoor air quality I would suggest that the old, ancient actually, technology of adiabatic or evaporative cooling might be considered.  Although adiabatic or evaporative cooling can provide effective temperature control in vast parts of the United States it can also provide an extremely effective filtering system as well.  Air is literally "washed" as it passes through the unit.  As part of an overall system where the adiabatic or evaporative cooling system, such as the Alton or Aztec products, only provides the ventilation air and other equipment handles sensible and latent cooling the improvement in indoor air quality could be dramatic.

Aztec Evaporative Cooling Solutions, a Mestex (Division of Mestek) company, will be exhibiting their evaporative cooling solution for data centers at the Data Center World Conference and Exhibit. Aztec will be located in booth 835. The exhibit will be March 20-21, 2012, at the Mirage Events Center in Las Vegas. Information about Data Center World can be found at www.datacenterworld.com.

Mestex, the Dallas division of Mestek has created a YouTube channel, MestexHVAC (http://www.youtube.com/MestexHVAC?feature=guide).  Mestex will start using this format website to post informational and promotional videos.  Current videos include information about the LJ Wing MV coil, the Applied Air Dedicated Outdoor Air System, and the Adaptaire DDC control system.

This past week I was able to participate in the GreenBuild conference in Toronto.  This was my first opportunity to attend and I have come away with a few impressions.

First, I was surprised at the sheer size of the exhibit area.  The Metro Toronto exhibit hall is quite large and split into two sections spanning the CN Rail lines in downtown Toronto.  Both sections were completely full with exhibits for everything from flooring to roofing and everything in between.  All exhibitors promoted the "green" or "sustainable" aspects of their products...even if those aspects might not have been obvious on first or even second thought.  In addition to the three Mestek HVAC product booths the exhibit area included product displays from most of the major north American HVAC manufacturers. 

The HVAC equipment companies, as well as many of the lighting and appliance companies, shared one common thread.  That is the emphasis on the "man-machine interface"...how the user interacts with the equipment for control or information.  Touch screen displays were everywhere providing access to virtual control points and providing occupant feedback on temperatures and, most importantly, energy utilization.  The degree of sophistication of the displays varied but the message was the same...in order to conserve energy people must have some sense of how much they are using.  It goes back to the old saying that "you can't manage what you can't measure".  The use of energy metrics have been proven to change occupant behavior and the HVAC industry is stepping up to help with that effort.

Mestex started our efforts in that regard several years ago with our Adaptaire DDC control system and we currently provide basic control and trending information via the Internet.  More developments are underway to further enhance the user feedback and help focus their attention on conservation of our energy resources.

Mestex has been providing this open protocol system for almost 10 years and has successfully integrated with virtually every other major control protocol on the market.  This has allowed building owners to gain visibility into the various Mestex brand products through their own building automation system in order to provide a richer set of points for monitoring and control.

Well, it looks like the IP lawsuit fever has spread to our industry.  The company IntusIQ has filed suit in Texas against Ingersoll-Rand, parent of Trane, and Schneider Electric, parent of APC, claiming patent infringements.  The infringements are related to the application of "mesh networks" for building control schemes.  Most of these things get settled out of court with some sort of licensing fee arrangement but with the current trend of suing over IP reaching a fever pitch in other industries this might mark the beginning of something that will impact the HVAC industry as well.

We have been promoting the Aztec evaporative cooling line to the data center market lately due to the increased interest in using outside air to cool the equipment under the new ASHRAE guidelines.  The Aztec product line also has a strong history in other applications…notably schools and prisons (interesting comparisons could be drawn there).  Over the last couple of years we have seen more and more articles describing indirect evaporative cooling systems as the solution for high LEED certifications and “green buildings” in general due to the performance and lack of any refrigerants in the system.

In order to provide better service to these markets we have improved the technical literature, brought on a temporary design specialist to document the current product design for better manufacturability, and made the unique DHTD burner technology and our DDC controls standard. 

We have now taken another step to make the product easier to apply by architects, engineers, data center designers, and advanced mechanical contractors.  The Aztec line now has Autodesk Revit BIM objects available in Autodesk SEEK for direct download into projects.  The BIM objects can also be loaded directly from within a Revit design project.

These objects join the other Dallas products that have BIM objects available.  Those include our most common direct fired heating units, our most common air turnover units with cooling, the entire Wing VIFB line, and the IFL split system DOAS unit.  As with all of our BIM objects the Aztec objects include “I” details such as cfm ranges, weight ranges, Tech Guide URL links, heating or cooling capacity ranges, cabinet materials used, and relevant agency certifications. 

The link below takes you to the Autodesk Revit site and the Aztec product listing.  The RFA files can only be opened using Autodesk Revit but the PDF product catalog can be opened and the general description info on the page can also help a designer consider the Aztec for his/her project.

http://seek.autodesk.com/search/aztec?source=SearchBox

For those who might not have seen this through their own trade associations here is an announcement of a program being planned by the US DOE. It sounds similar to programs in some European countries. There is a link to a webinar for more information about the proposed program.

The U.S. Department of Energy (the Department) is planning to develop a voluntary national Asset Rating Program for Commercial Buildings (AR Program). Through the AR Program, DOE intends to establish a building Asset Rating system that can be broadly applied to both new and existing commercial buildings, and provide affordable and reliable information to building stakeholders. The AR Program will inform building owners about the energy efficiency of their building systems, enabling comparison of the energy performance between buildings while accounting for differences in building operations and occupant behavior. The intent of the AR Program is also to help building owners identify opportunities for energy efficiency improvements.

DOE seeks the input of stakeholders and interested parties, and has issued a Request for Information (RFI) to solicit input on key issues associated with the development of an AR Program. DOE will be hosting a webinar for interested parties on August 23, 2011, at 12 p.m. (ET) to facilitate discussion on this issue. To attend the webinar, please register here to receive further information.

This particular article might get a little more technical than some previous articles but a recent visit to California prompted me to put this together. 

During a meeting with a consulting engineer I was told of a problem that he was having with a direct fired make-up air unit…not one of ours but the principles are the same.  The issue was a burner that would shut down for “unknown reasons” shortly after coming on-line.  After some discussion the engineer stated that his estimate of external static pressure was wrong because the unit was not installed as he had originally designed.  The duct system attached to the unit had several more bends in it than he designed and thus the external static pressure was higher than he estimated and higher than the manufacturer was told at the time of production.  This was the clue we needed to help the engineer understand what was going on.

Almost 10 years ago the safety standards for direct fired equipment were changed.  As a result most certified direct fired equipment provides heated air that is extremely safe from carbon monoxide, carbon dioxide, and other gaseous contaminants.  That is because the direct fired product is designed to meet a specific set of operating conditions, by code, that assure a velocity across the burner that is roughly 2,800 to 3,200 feet per minute.  When a direct fired product operates in that range then the combustion is “clean” and harmful byproducts are not produced in any significant amount.

In order to assure the user that the direct fired burner is operating in the proper range the manufacturer uses the total static pressure that is calculated for the unit (including the external static pressure) to size the airflow opening across the burner to stay within the target range.  Most manufacturers will size the opening to land in the middle of the range so that there is some room for minor errors in the estimates. 

In order to make this even more fool-proof the safety standard required manufacturers to add pressure switches to the units that would shut down the burner if the velocity across the burner was either too high or too low.  In the case that this engineer was describing the overly high external static pressure was causing the velocity across the burner to be too low and the burner would shut down.

Because the code and testing standards required manufacturers to be very specific you will find that the acceptable range between high and low is unique to each model and size in a product line.  Some of these ranges are very narrow…less than 0.25 inches of static from the high set point to the low set point.  This gives the equipment only 0.125 inches of static from the midpoint to the trip point in either direction.  Too many bends in the ductwork can easily add that much static to the system and cause the premature shutdown of the system.