Retrocommissioning Findings: Scoping a Dental Clinic VAV Reheat System–Part 1

I’m currently involved with a number of field oriented classes in which the instructors mentor the students through a retrocommissioning process on a system in an existing building in real time.  Based on past experience with this process, I have discovered that one of the things that seems to help the students succeed is to provide what I termed a Project Guidance Document that helped them put the clues together for the system they were focused on.  

The “trick” seems to be to develop the clues in the context of the facility they are working in;  i.e. using the utility consumption patterns, system types, etc. that exist in their facility.   But, to make sure that we don’t steal their fun and give away (what we, at the time, believe to be) the answers, the clues need to be illustrated by examples from other, similar facilities.

While discussing this with the team I am working on for a class down in the Monterey, CA area (really rough job; I have to go spend time in Monterey to do the project) we realized that if I did the Project Guidance Documents as blog posts, there would, potentially be benefits in the bigger picture.   Thus, the origin of this post.


The links below will jump you through the post.  At the end of each section, a “Back to Contents” link will bring you back to here.

It should be noted that this post is being developed based on a specific system in a specific facility that I am involved with currently.   But the concepts we will be discussing could be applied to identify opportunities in a VAV (Variable Air Volume) reheat system in just about any type of facility.  In fact the specific techniques could also be applied to just about any air handling system that had the capacity to simultaneously heat and cool, including systems with a preheat process, double duct systems, and multizone systems.  And the general concepts could be applied to just about any type of system, something I will be illustrating in subsequent posts.

The Facility’s Mission and its Resource Consumption Implications

The facility we are looking at is a Dental Clinic;  i.e. a facility with a medical mission.  As a result, the codes and standards it has to comply with might drive it towards a higher energy intensity than a typical commercial building.  For instance, filtration requirements may be more stringent, which can result in more fan energy spent moving air through the pressure drop represented by the filters in the system.  And temperature and humidity tolerances may be tighter than a commercial building in order to minimize the chance for infection and ensure patience comfort. 

Requirements of this type typically mean the systems serving a facility of this type will tend to be more complex and energy intensive that the systems in a typical commercial building.  That means that there are potentially more opportunities to optimize set points and operating parameters so that the required targets are met but not exceeded.   And it means there could be more things to go wrong, resulting in energy waste.

The bottom line for this heading is that the very nature of the facility makes it a good candidate for assessment since it, by nature, will tend to be energy intensive.

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Average Daily Consumption Patterns

To set the stage and help you understand what caused us to focus on the VAV reheat system in this facility as a potential EBCx (Existing Building Commissioning) target, I need to share the clues that were developed from the benchmarking, utility analysis and document review efforts that were undertaken as first steps in our project.  The utility analysis and benchmarks that follow were developed using techniques I have discussed in a number of other posts, including Developing Retrocommissioning Implementation Budgets; Establishing the Big Picture and Retrocommissioning Findings: Make Up Air Handling System Simultaneous Heating and Cooling – The Clues – #5 – The Utility Patterns Show High Baseline Consumption Patterns.

As a starting point for our initial assessment of the Dental Clinic, Brian and Jay, two of the team members I am working with on the Monterey project, had loaded utility data from the facility into the California Commissioning Collaborative Utility Consumption Analysis Tool (UCAT).  I took their results and added the degree data patterns for Monterey to developed the following graphs.


The electric patterns revealed that the facility tended to use electricity at a fairly steady rate that was not much influenced by the need to heat or cool (as indicated by the heating and cooling degree day lines).


The thermal patterns showed a bit more correlation with the need to heat but during the warmer months, the facility seems to use a significant amount of thermal energy relative to the peak that occurs in the cooler months. 

Both patterns indicate that some sort of change happened between  2013 and 2014 that caused the consumption patterns to shift downward.  The change may have been climate driven, especially the thermal consumption change since the 2013 heating degree day totals were higher than the 2014 heating degree day totals.  But other factors may have come into play.  For example, maybe there was a change in the use pattern for the facility or perhaps some sort of energy conservation work is already in progress.

If the latter is true, the opportunities for our EBCx project could be limited simply because someone is already working towards the same goal.  But if the former is true, this could be a great time to be doing an EBCx project because it will allow us to adapt the facility to the new patterns of use.

At this point in the analysis nothing is very specific.  In other words these patterns are potential clues about trends in the facility but they do not give us what we need to develop a firm conclusion regarding how the facility uses energy and the magnitude of the savings potential. 

For instance, we don’t really know if the electrical pattern is the result of a huge facility with no cooling plant that uses energy very efficiently or a tiny facility with a modest cooling requirement that is constantly using a significant amount of energy.  But when you start looking at the utility data in the context of other indicators, like the Energy Use Intensity factor (EUI) associated with a benchmark or the climate extremes or the types of systems that exist in it based on the construction documents, things may start to add up.

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The UCAT tool we used to create the Average Daily Consumption graphs makes it easy to move on and do a benchmark since the spreadsheet tab with the data behind the chart totals up the annual consumption as you enter the utility bill data.  So, my next step was to use those totals along with the building square footage to develop benchmarks using the DOE Building Performance Database tool I mention in the referenced blog posts.  The following slides show the various benchmarks I looked at.





As you can see, the clinic did not benchmark particularly well with regard to any of the peer groups or resources I compared it too.  This was an indicator to all of us working on the project that there likely would be opportunities to save both electrical and thermal energy moving forward.

In case you are wondering, I created the bar charts by loading the data from the DOE database into a spreadsheet tool that I have set up for the purpose. I could have simply used a screenshot from the web site …


… but I wanted to focus on the histogram and add my particular building to it for the presentation I was doing.  I get the data associated with a particular bar on the web site histogram by hovering my cursor over it as illustrated in the screen shot.

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Energy Analysis Conclusions

The poor benchmarks added a dimension to what we saw in the average daily consumption analysis.   In other words, the facility uses more energy per square foot than its peers.  So, it is possible that the high, relatively flat electrical baseline we saw in the average daily electrical consumption graph is the result of a number of things that could turn into opportunities including:

  • Incandescent lighting instead of a lower energy alternative,
  • Systems that are not scheduled,
  • Systems flowing water and air against higher than necessary pressures,
  • Systems that are simultaneously heating and cooling, 

I could go on but you probably get the idea.  The fact that the thermal consumption pattern does not drop to zero when it is warm outside could also be explained by simultaneous heating and cooling. So, to my way of thinking, things are starting to add up and provide some focus for a project.

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Bringing Climate Into the Picture

Another thing that may help us gain some insight into how the facility might use energy is to look at the climate pattern associated with it.   For instance, if the climate is hot and humid, the systems may not have an economizer process, so no opportunities there even though economizers are frequently found to be dysfunctional.  But if comfort is to be maintained, some simultaneous heating and cooling may be a necessary evil, and there may be opportunities to optimize the processes and minimize the need for it.

In contrast, if the climate is dry and mild, while some simultaneous heating and cooling may be necessary (and thus opportunities to minimize it exist), the real savings potential for the air handling systems may lie in ensuring the economizer processes are working properly.

The daily and seasonal climate patterns will likely drive the loads on the air handling systems in most facilities to some extent.  One of the advantages of VAV systems like the one we are going to focus on is that they are designed to follow those load swings.  So understanding one of the drivers behind them will be important.

Hourly Climate Data

One way to gain some insight into the climate is to take a look at a couple of years worth of hourly climate data.  I walk you through a process that can be used to procure that kind of information in a previous post, so I won’t repeat myself here.  But, if you were to do that for Monterey, CA, the location of the facility in question, you would find something like what is illustrated below, first for 2014 and then for three years.



I typically will develop a chart like this for a place I have not visited previously because it gives a perspective on the climate and how dynamic it is;  basically, how big the daily spikes are and how much difference there is between the peak and valley of the annual wave form. 

Below, presented in a similar format to the preceding (but for two years instead of three) is data for Atlanta, Georgia, which gets much hotter and more humid than Monterey and is also somewhat colder.  As you can see, the patterns are quite a bit different, so the opportunities in one location might be different from the other even if the system type is the same.


Looking at the climate in this way also gives me some perspective relative to some important operating metrics like:

  • The freezing point of water (dashed white line),
  • The design conditions (dashed red and blue lines) vs. extremes conditions (points where the orange dry bulb temperature line overshoots the dashed lines), and
  • The generic 75°F space (the dashed green line). 

In addition, the data file behind this chart can come in handy later in the project as a way to do hour by hour energy calculations to identify energy consumption for a particular year.

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Bin Climate Data

Another way to look at the climate is bin data.  I have a blog post or two about that topic also, so no need to repeat it here.  But if you looked at the Monterey climate as bin data, it would look like this, first in a tabular form and then in a graphic form.



The data in the table is a convenient way to do energy calculations for a typical year.  In fact, back in the “olden days” when a spreadsheet was a piece of graph paper and the microprocessor driving it was your brain, a slide rule, and maybe a four function calculator, this was one of the few practical ways to do an energy calculation. 

Data in this format is also is what you need to determine an appropriate outdoor air dry bulb economizer limit set point.1

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Bin Climate Data and the Psych Chart

Having said all of that, for me, the fastest way to get a “visual” on the climate for a given location is to use the Bin Plot feature found in many electronic psych charts.   Here is the bin plot for Monterey, CA courtesy my copy of Akton Psych Chart.2


The plot is generated by dividing the climate data into “bins” that are, in the context of the chart, 2°F wide by 5 grains per pound high (there are 7,000 grains per pound so this is just another way of saying pounds of water per pound of air).  The squares are then color coded as a function of the number of hours at the condition associated with the box.  Warmer colors meaning more hours. 

In the plot above, the blue squares represent the least hours (1-42 hours at the condition covered by the square) and the red squares represent the most hours (337 to 338 hours at the conditions covered by the square).

Adding key parameters like the design targets, the “generic” ASHRAE comfortable space target, and the line where water would freeze gives me a quick visual on how extreme the climate is relative to the parameters.   Adding the ASHRAE comfort zones can add a bit more insight, as illustrated below.3


One way of looking at the chart above is to say that if you are in Monterey on one of their extremely hot and humid days and want to be comfortable, you should go stand out side.

To give you some perspective, here is the bin plot for Atlanta, Georgia with the same information on it.


It’s a totally different experience to go stand out side in Atlanta on one of their extremely hot and humid days.  If you have been inside a conditioned space, you glasses fog up because at 72°F or so, they are below the dew point of the outdoor air.

The bottom line is that climate will have an obvious impact on how the HVAC systems in a facility use energy and if you are undertaking a project where you are trying to optimize the use of energy, then the climate you are dealing with on the project may influence where you head in terms of your initial investigations.

For example, if the dental clinic we are talking about was located in Atlanta, Georgia, the fact that the ventilation air provided by the air handling systems would be  hot and humid and/or cold and dry a lot of the time might cause me to initially focus on the 100% outdoor air systems and the minimum outdoor air flow regulation for economizer equipped systems.  The reason for that focus would be that if the heating and cooling set points were not correct or optimized for the application and/or the systems were handling more outdoor air than was needed, then I might have significant energy savings potential that I could achieve by making appropriate adjustments in those areas.

In contrast for those types of systems in the Monterey, California environment, the impact of non-optimized set points and excessive outdoor air is less likely to be significant for several reasons.  For one thing, most of the time, the outdoor air is at or near the supply temperatures that would typically be required by the facility. And, because the climate is so mild, economizer equipped systems would tend to spend very little time on minimum outdoor air, so an improper setting, while worthy of attention and adjustment, would not be as significant in terms of delivering savings as it would be in Atlanta. 

In contrast, poor or missing blade seals on the return dampers in an economizer equipped system in Monterey could significantly compromise its ability to deliver “free cooling” because in the 100% outdoor air position, the system would not really be delivering 100% outdoor air.  For example, if an integrated economizer equipped system was trying to deliver 57°F at the cooling coil discharge and had 15% return air leakage, then it probably would run its mechanical cooling for 1,200 – 1,300 more hours annually than would be necessary if the leakage were corrected.

In contrast, a similar system with 15% return damper leakage and a 57°F cooling coil discharge requirement in Atlanta would use mechanical cooling for 300 – 500 hours per year when it didn’t have to due to the blade seal leakage.  So, while the problem is worth fixing, its not nearly as significant as it would be in Monterey.

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The Bottom Line Up to This Point

Lets tally up our clues and the direction they are setting for our investigation at this point.

  1. We are dealing with a facility that, by the nature of its mission, will tend to be more complex and energy intensive than a typical commercial building.  Thus, there are likely more targets for optimization in terms of delivering the desired level of performance as efficiently as possible.  
  2. The sophistication and complexity of the systems that might existing in a medical facility also means there are probably more things that could go wrong with them, resulting in energy waste.  From the perspective of our project, those potential failures are potential opportunities for us to set things right.  Doing that will include documenting the problem and its resolution and then providing the training and other resources necessary to ensure the benefits of our effort persist. 
  3. Our benchmarks tell us that the Dental Clinic we are looking at is using more energy than its peers.  That alone tells us that there are likely going to be opportunities to save energy in the facility.
  4. The peer group we used includes facilities from across the country.  So, the fact that the Dental Clinic we are focused on is in a mild environment and has a poor benchmark relative to facilities that might be located in more extreme climates only makes the argument that energy savings are likely more compelling.
  5. The electrical consumption pattern on an average daily basis is fairly flat and does not appear to be driven very much by the climate.    Frequently, when combined with a high benchmark, this means that there are opportunities related to scheduling, opportunities to minimize pressure drops,  opportunities to get variable flow systems to track the load profile, and opportunities to optimize flow and temperature set points.
  6. The thermal consumption pattern on an average daily basis shows a tendency to follow the climate pattern. So improvements in things like the boiler efficiency could potentially deliver savings on a year round basis.
  7. The thermal pattern on an average daily basis, while seasonally driven, also is somewhat high during the relatively warm months of the year, months when little if any heat should be required to offset envelope losses.  Frequently, a pattern like this is associated with simultaneous heating and cooling. 

Points 6 and 7 are particularly important for our focus project.  Past experience and industry metrics demonstrate that unnecessary simultaneous heating and cooling is a common problem, especially in medical facilities. 

And the problem can be fairly insidious because dysfunction in one process is masked by an equal but opposite dysfunction in another resulting in a comfortable, productive environment at the zone level, but one that is delivered in a very energy intensive manner. As a result, in a facility were the performance of the HVAC system is assessed by how well it is meeting the requirements at the end use location, unnecessary simultaneous heating and cooling can go unnoticed.  

Given that our target facility is a medical facility and the ventilation, temperature, and humidity control requirements associated with facilities of that type, it would not be surprising to find that the HVAC systems installed to serve it have the potential to do simultaneous heating and cooling at a number of points in the air handling process. 

For instance, if the HVAC systems need to handle a lot of outdoor air, then they may require a preheat processes to bring the ambient air up to an appropriate temperature for use in the facility and to prevent freezing of other heat transfer elements in the system during extreme winter weather.  By nature, a preheat process should never be active at the same time as a cooling process, like an economizer cycle or a mechanical cooling cycle.  But if something has gone wrong, that very well could be occurring, resulting in unnecessary simultaneous heating and cooling.

Having said that, in the context of delivering a safe, comfortable, productive, environment, simultaneous heating and cooling is sometimes a necessity, especially in a medical facility.   Usually, it manifests itself in the form of:

  • A cooling process applied to drive the air temperature down as far as is necessary for dehumidification, followed by
  • A reheat process applied maintain comfort when the cool air is delivered at the required ventilation rates and provides more cooling capacity that the zone requires at the time.

For such a process, the energy conservation opportunities typically are things that minimize the use of reheat via temperature and flow set point optimization rather than via eliminating the process.  It may also be possible to provide the required heat using recovered energy or solar energy.

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Reviewing the Facility Documentation

Before heading out into the field, taking a few minutes to look at the documentation for the project, especially in light of the information gleaned from the utility analysis will be time well spent.  For one thing, the process will help you gain a deeper understanding of the facility.  And, it may help you further focus your field time.  

For instance, if your time will be limited, you may want to have a sense of which systems, mechanical spaces, and other areas you want to visit first.  And, in the course of reviewing the documents, you may also decided some spot measurements would be useful, or even a bit of data logging. 

Equipment Schedules; Valuable Information in a Concise Package

Frequently, one of the first things I will look at in a drawing set is the equipment schedule.  The information it contains can tell you a lot about the design intent for the facility and may also shed some light on where energy might get wasted.

Given the clues about the potential for simultaneous heating and cooling in the Dental Clinic, one of the first things I looked at in the drawing set was the Air Handling Unit schedule.   Here is what I saw when I did that.



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Not Your Normal Units of Measure

One of the things I noticed right off the bat was that this project happened when GSA and other government agencies were trying to use the metric system.  So, I made sure that my copy of Versaverter4 was installed on my new laptop and that I had a units conversion app on my iPhone.  I also made a mental note to try to remember the numbers I was looking at were not the units I am used t0;  no need to be half way through an energy calculation and then realize that the “3,000” behind the whole thing was liters per second, not cubic feet per minute. 

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The Unit Must Have an Economizer

The second thing I noticed was that the unit had a minimum outdoor air quantity specified that was less than supply air quantity.  That implies that the unit has an economizer. Given the mild environment, a working economizer could be a real asset.  One that was not working could cause the chiller to run more often that it needed to, which could be a cause for the high electrical consumption and poor benchmarks. 

When I went out into the field, I was going to be around the project site for a almost a week.  So I decided it might be worth deploying a few loggers while I was there so I could do an economizer assessment.  More on that later in part 2 of this post.  The point here is that I learned something from the drawings that complemented my analysis in the context of a potential energy waster (a dysfunctional economizer) that, if it existed, could be corrected using the low-cost/no-cost techniques associated with EBCx.  It also helped me plan for a  little field testing while I was there.

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The Unit Does Not Appear to Have a Preheat Coil

The schedule also shows that the unit only has a cooling coil in it.  So, while it doesn’t mean there absolutely is not a preheat coil ahead of the unit (something that I could quickly verify on the drawings and in the field), it is less likely that the unit is wasting energy by doing preheat concurrently with a cooling process.

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The System is Intended to be Variable Volume

You can’t really tell this from the AHU schedule all though the fact that the fan is to be direct drive implies that a variable speed drive of some sort will be provided.  But, the reason I reached this conclusion is that a little further into the drawing set, I found an Air Valve Schedule.


I’d gone of looking for it, sort of “following my nose” as Jay Santos would say because I was wondering if the system was VAV.  I also was looking for a way the system could simultaneously heat and cool and I had ruled out a preheat process.  Finding the air device schedule showed me that the designer intended the system to operate as a VAV system because the terminal units have a different maximum an minimum flow setting.  If the system was supposed to be constant volume, both the minimum and maximum flow would have been the same. 

The Air Valve Schedule also revealed that the system was set up to simultaneously heat and cool.  Given the need to make a safe and comfortable environment and the need to comply with various health care codes, some reheat would likely be necessary. 

But frequently in existing buildings, there are opportunities to optimize the way the terminal units are working, thereby minimizing the energy intensity associated with a reheat process.  And frequently, the improvements can be made via low-cost/no-cost strategies like like calibrating the flow and temperature sensors, adding CO2 sensors at appropriate locations to allow demand controlled ventilation to be implemented, and optimizing the central air handling unit supply temperature and pressure control processes.

Having found another one of the sources of potential inefficiency that I had been looking for, I decided I would spend some time looking at what the terminal units were doing while I was on site.  I could start the process by surveying the supply temperatures from the diffusers with my infrared thermometer and then comparing those temperatures to the supply temperature from the system. Based on those results, I  might decide to deploy a logger or set up some trends to tell me what was going on with the terminal units over time.

So, once again, spending time up front with the drawing set had helped me focus my effort and plan my field activities.

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The Unit Has Multiple Filter Banks

As I was paging through the equipment schedule sheets looking for the Air Valve Schedule, Another thing caught my eye;  the filtration schedule.


There are a number of reasons I was interested in this.  For one thing, as you may have discovered if you follow the blog or attended the session I did this year at the National Conference on Building Commissioning (NCBC), filters represent an opportunity to save resources on a number of fronts.  This is especially true for systems with high efficiency filters and/or multiple filter banks. 

To figure out what the savings potential is, you have to know the details of the specific filter that is being used, how it has been applied and how the filter banks are configured (there’s more on this in the NCBC presentation if you are interested).  So, I made a note to make sure I took a look at the filters while I was on site so I could gather the information I need to run the analysis.

The other item that caught my eye was the laminar flow filter diffuser modules specified for some of the general dentistry areas.  For one thing, I have run into instances where the maintenance staff did not realize that this type of equipment existed since it is not in a mechanical space and from the zone, looks just like any other diffuser.  As a result, in these situations, the modules were in need of service. 

For another thing, the pressure requirements of the modules could be what set the pressure requirements for the VAV fan system.  In other words, because fan power is a direct function of static pressure …


… if the pressure requirements of the two zones with the filters (about 1,000 of the 16,000 cfm handled by the system under design conditions) set the system static pressure for the entire system, then it might be worth figuring out how to minimize their impact.

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The System Has a Return Fan

Right below the filter schedule was a fan schedule.


One thing that jumped out at me was that there was a return fan.  The reason this caught my attention is that one of the real tricks associated with getting a VAV system to work is to get the flow produced by the return fan coordinated with the flow produced by the supply fan and the minimum outdoor air requirement.  

To much return flow means you are not going to get the necessary ventilation in to the building.  If things go too far amok, the return fan can actually move more air than the supply fan, pressurizing the outdoor air intake system and eliminating the formal introduction of outdoor air into the HVAC system.   That, of course, could be an Indoor Air Quality (IAQ) concern. 

But, since the air had to come from somewhere, it may also mean there is a pressurization problem causing outdoor air to infiltrate into the facility with out being properly treated.  That can cause mold and mildew problems in the envelope in hot and humid climates, freeze pipes in cold climates, increase the perimeter load in all climates, and lead to general problems with occupant comfort.  In a medical facility, it can also cause infection control problems since air may move from a dirty area to a clean area instead of vice versa.

Many of the items I just enumerated are not energy savings targets.  In fact, if they exist, then fixing them might actually increase energy consumption.  But the reason we put HVAC systems into buildings is to make them safe, productive, comfortable working environments.   If they fail to perform in that manner, then we might as well not have installed them in the first place. 

Making sure the building is safe, productive and comfortable is an important element of any commissioning process.  And because of that, I planned to spend a little time trying to under stand how well the return fan was working with the supply fan in terms of managing air flow.

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Assessing the System Configuration

If you follow the blog and/or know me, you know that I am a big advocate of the System Concept and System Diagrams.  It is often easier to develop  a first draft of a system diagram from project documents and then verify it in the field.  As a result, I frequently start developing mine while I am working my way through the documents. 

A good starting point in some instances is the system diagram included on the contract documents, if there is one.  These are often called “System Schematics” or “Flow Diagrams” or Riser Diagrams”.  While the documents I was working with had “Flow Diagrams” for the piping systems, they did not have one for the air handling system.

That’s the bad news.  The good news was that the drawing set included control drawings and fairly detailed ones at that. And there was a schematic and sequence for the air handling unit included in that documentation.




This was good news on a number of fronts.  For one thing, it meant that the engineer of record had not abdicated their authority to the control contractor in terms of the control system design.  Rather, they had taken the time to develop a detailed set of control system documents, documents with critical design intent information in them. 

This is becoming more and more rare in the industry these days and in my opinion, is one of the reasons we have some of the problems we have.  That said, the Owner has to provide the budget and time for the process and frequently, they are not doing that.  As a result, the design responsibility ends up shifting to the control contractor, who may have a fine product line and top notch technicians, but who really does not know the nuances of the mechanical design since they are not the engineer of record.

I will step down off of the soap box now, but bottom line, I was really pleased to see this level of detail in the design documents.

What was missing, from my perspective, was a diagram showing the entire air handling system.   The diagram in the documents showed the air handling unit, but did not show, for instance:

  • How the zones were integrated with the unit,
  • If the zones where identical or varied in terms of how they worked,
  • How the air that came in through the minimum outdoor air damper got back out of the building

In other words, it did not show the air handling system.  So, using the diagram as a starting point, I made a first pass at developing a system diagram that included some basic zone information along with the performance metrics for the equipment.  Here is the current state of affairs in that department.


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Exploring the Other Systems

This particular post is focused on scoping air handling systems, in particular, the VAV reheat air handling system associated with the Dental Clinic. But after completing my utility analysis effort, I explored the other systems in the facility also.    Generally speaking, I was using the same techniques that I have illustrated in this post to develop targets in those systems.  I will discuss those that process in separate posts with a structure similar to this one.

Using the Evidence to Date to Develop a Financial Bottom Line

As you may recall from a recent post titled Developing Retrocommissioning Implementation Budgets; Establishing the Big Picture, it is possible to use the utility data, the owner’s tolerance for risk, industry metrics, and engineering judgment to begin to frame up the project budget.  After the efforts I described above, I was in a pretty good position to do that for this project, resulting in the projections summarized in this slide from one of the early training presentations from the Dental Clinic class.


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The Next Step – A Site Visit

Having developed a sense of the facility via the analysis techniques I have been discussing, I was ready for a visit to the site.   In the EBCx business, this visit is typically called a “scoping” visit.  The idea is to walk the facility looking for obvious signs of opportunity, perhaps guided by what your pre-site visit observations have pointed you at.

Having said that, its important to not let your pre-site preparation constrain you too much.  Otherwise, you might miss an opportunity that could be very significant, something that was not obvious from the paperwork you have been looking at.

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In the next post, I will share my site observations with you and give you a sense of where they would cause me to focus my efforts for the project.  Bear in mind that I am doing this to facilitate a hands-on training class.  So in this specific case, the idea is for the team working on the air handling systems in the class take those clues and run with them to develop their class project.  But in the larger sense, many of the things I will discuss are common opportunities in VAV reheat air handling systems as well as other multiple zone system types.


David Sellers
Senior Engineer – Facility Dynamics Engineering

Click here for a recent index to previous posts

1.    For more on this subject, visit the Functional Testing Guide chapter on the Economizer and Mixed Air section of an Air Handling Unit and read Steve Taylor’s ASHRAE Journal article titled Why Enthalpy Economizers Don’t Work.  Note that you need to run the Functional Testing Guide in Compatibility View to get it to work in newer versions of Internet Explorer. (Back to reference point)

2.    If you upgrade the free Greenheck electronic psych chart to the Pro version, you will get this feature along with many others at a bargain price compared to what an Akton Psych chart seat would cost.   It turns out that the Greenheck Chart is a subset of the Akton chart focused on HVAC processes.  So for someone in our business, the Pro upgrade is a really good deal. (Back to reference point)

3.    Bear in mind that by definition, if you are in one of the comfort zones 80% of sedentary or slightly active persons find the environment thermally acceptable.  That means that 20% of the people will not be comfortable. (Back to reference point)

4.    I found this little free software package on my first metric GSA job around 2001 and have been using it ever since.  You can still find downloads for it out on the net but the original developer ( seems ot have moved on to other things.  I just installed a copy on my new Window’s 8 machine and it seems to run O.K. other than a little message that I think is saying it can’t find a file so its going to make one.  I seem to have solved that by locating the application in a folder in the root directory of my C:/drive. (Back to reference point)

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