The Persistence of the Benefits of Commissioning (Plus a Few Pictures of Legacy Instruments)

As you probably have noticed if you follow the blog, I love finding old instruments in my travels. I have even been lucky enough to save a few of them from the dumpster, like this resonant frequency-based tachometer …


… or this Foxboro pneumatic proportional plus integral (PI) controller …



… or this 1970’s vintage central control panel (the state of the art about the time I entered the industry).


Just the other week, I was in a building down in San Francisco that had originally been built in the 1960’s by Bethlehem Steel as their headquarters on the West Coast.

That was of unique interest to me because my grandfather on my mother’s side was a welder for Bethlehem Steel in their Johnstown Pennsylvania plant around that time; who knows, maybe he made some of the welds in the steel for the building when it was being fabricated back then. (The picture is from one of the elevators; they feature different vintage photos related to the building’s history).

The central plant in the facility had been recently upgraded from the original system. But when we got to the basement mechanical space, I was treated to a few more legacy control components, including this 2-pipe indicating temperature transmitter …


… and another central control panel.

The last picture is an interesting juxtaposition of technologies; the two monitors and the black box behind them (a PC) contains many orders of magnitude more information than the legacy control panel behind them. But I still have a soft spot for the legacy panel and was glad to see that it had been retained when the plant was upgraded.

My reason for bringing all of this up is that about a week ago, Steve Briggs, one of the other FDE engineers that I have the privilege of working and teaching with on occasion, sent me a picture from the field of an old seven day timeclock, the type of device we used to schedule equipment back in the “olden days”.

The device was simply an electrically driven clock with a dial that made 1 revolution every 7 days. Small, adjustable “trippers” were mounted on the perimeter of the wheel with little thumb screws and were shaped so that the side visible to you pointed to the time setting you desired and a little lever on the back of them would trip another lever (which is concealed behind the dial in this picture). The concealed lever, in turn, worked a mechanism that would open and close contacts, thus turning things on and off on a schedule.

There were typically two different types of “trippers” (some people called them “dogs” for some reason). On the visible side, they were different colors, usually black and silver so you could tell them apart.

On the back side, the shape of the lever was different with the difference being that one type of tripper would move the concealed lever in a way to turn close the contacts that the clock controlled while the other type of tripper would move the concealed lever in the other direction, opening the contacts back up. The contacts, in turn, could be used to turn equipment on and off on a schedule. You can still find devices similar to this in the hardware store, targeted at controlling the lamp on your end table.

The brass screws you see below the dial are one side of a number of contacts. In other words, if the picture were zoomed out a bit, you would actually see two rows of screws, with each vertical pair corresponding to an independent contact. In this case, I believe the last pair of screws on the far right would the power connection where you landed the 120 vac power to run the clock.

When I saw Steve’s e-mail and the picture, it immediately reminded me of my very first exposure to the concept of persistence of benefits. In other words, it’s one thing to intend to have a building or system do something like operate on a schedule by providing a time clock with a wiring diagram and control sequence that indicates that the clock should start or stop a piece of machinery or cause a certain function to happen at a certain time of day on a certain day of the week.

But it turns out that it is entirely different thing to have that design actually work and remain in operation over time, something I really did not realize until I ran into my first time clock.

Specifically, in the fall of 1979 or so Chuck McClure sent me down to do field work at Kent Library on the South East Missouri State Campus.

Chuck founded McClure Engineering in 1953, the year before I was born. And, based on the recommendation of Dr. Al Black, a mentor and friend from my Park’s College days, Chuck had taken a chance on an Airframe and Power Plant mechanic with some engineering courses to his credit and hired me as an HVAC field technician, which is how I got my start in this industry.

The reason for the field work in Kent Library was that the University was interested in installing some sort of supervisory monitoring and control system to help them understand how their buildings were running from a central location and to allow them to identify operating problems and ultimately, optimize the existing stand alone control systems based on what they were observing. This, of course, was the fore-runner of what we take for granted now in our Direct Digital Control (DDC) systems. But at the time, it was fairly cutting edge.

In those days, large buildings might have central control panels similar to the ones I illustrated above. (And sometimes, the gauges were even right). But very few if any sites with multiple buildings, like a college campus for instance, had all of the buildings networked together and visible from a central location. So, it was exciting to be involved in a project like this, even though at the time, I did not fully comprehend how big a deal it really was. But eventually, Kent Library would become my first design for what we now would call a DDC system (under the watchful eye of Chuck and Al of course).

At the time of the site visit, my goal was to develop field verified diagrams for the existing interlock wiring and pneumatic control systems serving the equipment in the library. Thus, I found myself opening up control panels, junction boxes, motor control centers and wireways tracing out colored wires and copper tubes and trying to figure out what they were connected to and what all of these funny, new to me, electrical relays, switches, and pneumatic gizmos did.

The original library was dedicated in 1939. But all of the equipment I was looking at had been installed in a 1968 project that had been done by Chuck himself. So, I had a pretty good resource at my disposal in terms of trying to understand the design intent of the facility.

One of the things that had attracted me to McClure Engineering when I interviewed there was that they had always had an interest in energy conservation and the responsible use of resources, even before the first energy crisis hit in 1973. In the course of the interview process, Bill Coad pretty much said to me what would eventually become his Energy Conservation is an Ethic  paper and as a result, I left the interview inspired in a way that changed my life.

One of the reasons Chuck and the University had targeted Kent Library for the pilot for a supervisory control system was that it was fairly energy intensive due to the archival storage nature of the application. If you are playing the archival storage game, one of the things you are trying to do is hold very stable temperature and humidity levels and keep the air very, very clean. Avoiding damage by light and vibration are also important. It’s really pretty interesting (in a nerdy sort of way) and the ASHRAE Handbook of Applications contains an entire chapter dedicated to the topic.1

All of those requirements tend to mean that the HVAC systems in archival storage facilities need to run round the clock, especially in the rare book areas, even if nobody is in the facility. But if nobody is in the facility, then one thing you don’t have to do is ventilate; i.e. introduce outdoor air to manage the contaminates introduced into the built environment by human activity.

In climates like Cape Girardeau, Missouri, ventilation loads can be significant because it can be very cold and dry in the winter and very hot and humid in the summer, as illustrated by this bin data plot I created using the Pacific Energy Center psych chart tool.2

As a result, one of the things that Chuck had done in his 1968 control system design was include a time clock that would shut down the minimum outdoor air that was brought into ventilate the building during the unoccupied hours. In other words, even though the systems could not be scheduled, the ventilation could and Chuck designed the clock into the control system to perform that function

Since I was using the original design documents and control submittals for the 1968 project to guide my field effort, one of the things I was looking for was that time clock because we planned to take over that function with the central monitoring and control system. Doing so would allow us to change the schedules by remote commands from the central location rather than by having to put out a work request to have one of the campus technicians visit the building and move the trippers around on the time clock every time the school was not in session or a schedule changed.

Having to do that every once-in-a-while doesn’t sound like a big thing until you consider the number of buildings on a college campus and that each building might have multiple time clocks in it. The overview above will give you a sense of that. Each of the little markers is a building. Kent Library is the yellow marker to the upper right of the clump of red markers at the lower left side of campus.

Eventually, one of the control panels I opened up contained the clock I was looking for. But the problem was that it looked just like the clock in the picture Steve sent to me; i.e. there were no trippers on it. That meant that currently, at the time of my visit, one of Chuck’s energy conservation features was not delivering the intended functionality.

But it was worse than that. There was a small manila envelope sitting in the bottom corner of the control panel. Even thought it was not very large – maybe 1 inch by 2 inches – it was kind of heavy. I broke the seal and opened it up to discovered that it contained the missing time clock trippers. There were 14 of them to be exact; 7 silver ones and 7 black ones.

That was enough of them to program one on and off event for each day of the week, just as Chuck had specified. The problem was, that since they had never been installed on the time clock the ventilation that Chuck had intended to be shut down for about 6 to 8 hours a day on week days, longer on the weekend as I recall, had not happened, not even once, since 1968.

The good news there was that we had just found a significant opportunity to reduce the operating cost of the facility, which would definitely help justify our project. The bad news was that it should have been happening all along.

The incident certainly caught my attention, Chucks too. And as a result of the incident and other insights we were having as a company about the how buildings were being operated, Chuck tapped into my A&P Mechanic background and had me start developing checklists for some of our new projects.

We applied the lists as a tool to help us prevent problems like the one I had uncovered that day in Kent Library. We also made an effort to train the operators about the features of our designs, especially the ones that would help save energy.

And we worked with our clients to help them understand how to monitor the performance of the facility on a day to day basis by using average daily consumption analysis and supplementing their stand-alone control systems with remote monitoring systems like the one I was starting to work on for Kent Library.

As I look back on it now, I realize that a lot of the things we were doing to try to address the lack of persistence of the benefits of Chuck’s design are the same things that are suggested today in the commissioning industry to help ensure the persistence of the benefits of commissioning.

At the time, the commissioning industry was just starting to emerge in Canada and the United states. But since I had not heard about the commissioning industry yet, I thought that all we were trying to do was operate the building properly.

David Sellers, P.E., Senior Engineer

Facility Dynamics Engineering

Visit FDE’s commissioning resources website at

Visit my non-technical blog The Other Side of Life at

  1. It’s Chapter 33 in the most recent, 2015 edition of the Application Handbook. If you happen to be in the Bay Area, there are copies of different editions of the handbooks available in the Pacific Energy Center Resource Center. I think you can even check them out if you want to.
  2. To do the bin part, you need to upgrade the basic chart tool (which is free) to the professional version. But Ryan Stroupe, the Measurement Tools Program Coordinator that I teach with at the PEC, worked out a deal with Hands Down Software, the chart developer, that allows you to upgrade to the professional version at a 30% discount from the normal price.
Posted in Controls, Mentoring and Teaching, Operations and Maintenance, Pneumatic Controls, Retrocommissioning Findings | Leave a comment

Resources for the Resourceful – Utility Analysis Spreadsheet Tool

Authors Note: Since the point in time when I published this post, some of the links have expired. So, I have gone through it and renewed them and also made a few edits.

Linking to the Weather Data Depot in my previous post reminded me of another recently released free resource.  Several months ago, the California Energy Commission released the retrocommissioning toolkit on via the California Commissioning Collaborative’s website. The toolkit includes a number of useful tools, but the one that came to mind in the context of the previous post is the Utility Consumption Analysis Tool (UCAT).  Here is a screen shot of the raw output generated by the tool as used for a recent project.

The tool also plots the data in a basic chart, but I usually copy it into a different spreadsheet so I can have more control over the colors and arrangement, which are locked down in the tool to facilitate its automated operation. Here is what that data looks like in a standard energy analysis spreadsheet that I have, which I use early on in a project to help me understand how energy is used and the potential savings I might anticipate, and thus, the budget.

But bottom line, the arrangement of the spreadsheet allows you to develop the data you need and  plot a normalized graph of average daily energy consumption almost faster than I can type this.

You simply enter billing dates and the consumption for the billing period and the spreadsheet takes care of the normalization process, including filling in for missing months.  Several years of data can be plotted for comparison along with other data that you want to contrast with consumption patterns.

In the example above, I have plotted cooling and heating degree days. The degree data came from the Weather Data Depot site I mentioned and was added to the chart in my spreadsheet tool. But the UCAT tool includes a table that would allow you to add the data directly into the tool, which causes it to plot on the chart the tool generates, along with the energy data.

I could have also plotted percent occupancy, rooms sold, central plant energy, or any other monthly information that I had available for comparison using the empty table.

The bottom line is that the tool makes monitoring and analyzing your facilities energy consumption patterns a matter of a few simple key strokes.  For a discussion of ways to use this type of analysis to target commissioning and efficiency, opportunities and help them persist, see Using Utility Bills and Average Daily Energy Consumption to Target Commissioning Efforts and Track Building Performance, which is a paper I wrote on the topic for the International Conference on Enhanced Building Operations.

David Sellers, P.E., Senior Engineer

Facility Dynamics Engineering

Visit FDE’s commissioning resources website at

Visit my non-technical blog The Other Side of Life at

Posted in Excel Techniques, HVAC Calculations, Operations and Maintenance, Resource List and other Resources, Retrocommissioning Findings | Leave a comment

The AMCA ASET-US Conference and Mentoring

Earlier this year, I was asked to be the plenary speaker at the upcoming AMCA ASET Conference in San Antonio, Texas. As many of you probably know, AMCA is the Air Movement and Control Association International and their mission is to advance the health, growth and integrity of the air movement and control industry. That means they are very involved on a global scale with manufacturers of air system components; things like fans and ducts and louvers and dampers to name a few. So, being provided with the opportunity to attend one of their technical conferences was exciting to me and my only regret in accepting was that I could only stay for one day, having already agreed to teach several classes at my monthly gig at the Pacific Energy Center in San Francisco.

As you can see from the header image, the conference is rapidly approaching. But in talking with Michael Ivanovich1 earlier this week about my presentation, I found out that there still are slots open in the conference. In fact, Michael give me a discount code to share with you that will give you $50 off the registration fee if you are a non-AMCA member, taking it $450 down to $400.


The conference features two different tracks, Air-Systems Design and Air Products & Technologies. You can get a sense of that by visiting the conference web page or downloading the conference brochure. In my perspective, both tracks have interesting topics and great speakers and I will have a tough time choosing where to go for the time I am there. So, if you decide to attend, I don’t think you’ll have a problem keeping yourself busy.

And of course, attending a conference like this puts you in a great position to share what you learn by being a mentor to to the folks back at your home base. Mentoring is extremely important in terms of making the industry and the world a better place and is a major focus of my plenary talk.

For me personally, most if not all of any success I have achieved can be attributed to some very wonderful mentoring experiences like the one I wrote about previously in one of my blog posts. Working on my presentation for this conference has caused me to recall many, many, many of my mentors and experiences and as a result, I plan to start a series of blog posts dedicated to each of them. So stay tuned.

But bottom line on this post, if you work with air handling systems at a technical level as designer, installer, commissioning provider or in operations, this will be a great opportunity to learn a lot from some really knowledgeable people in the industry and earn up to seven Professional Development Hours (PDHs), something most registered professionals need to do to maintain the currency of their license. And like I indicated above, there are still slots open at the conference, rooms available at the hotel, and reasonable airfares available.

Hoping to see you there.

David Sellers, P.E., Senior Engineer

Facility Dynamics Engineering

Visit FDE’s commissioning resources website at

Visit my non-technical blog The Other Side of Life at

  1. Michael is a good friend but also happens to be the Senior Director of Industrial Relations for AMCA and the guy who got me started doing this blog and has mentored me through-out my writing career.
Posted in Air Handling Systems, Mentoring and Teaching | Leave a comment

Howden North America’s Fan Engineering Handbook

Authors Note:  So, some good news on this.  For a while, some of the links below did not work and I could not get information back from Howden regarding how to get a copy of the handbook since my contacts there had moved on.  

But on a lark, I did a search today and discovered that Howden is now making the 9th edition available electronically at no cost.  Just submit this form and you should get an e-mail with a download link.

I don’t know if they will continue to make a printed, leather bound version like the one in the picture available.  But if you are old and sentimental about books (like I am) you can still find used copies of it and earlier editions out there, as I mention in the blog post.  Prices seem to vary all over the place.

Since the electronic version I illustrated in the post is the 9th edition, I suspect the version you will get by following the link will be very similar if not identical.   I submitted the form myself and will update this note if I notice any major differences.


I realized the other day that the Reading and Resource list I posted does not contain information on Howden North America’s  Fan Engineering Handbook, so I’ll use this post to draw your attention to that valuable resource, which is pictured below.

Fan Engineering

Incidentally, folks my age and older may know this book as the Buffalo Fan Engineering Manual.  I believe Howden North America aquired Buffalo Forge at one point, thus the name change.  If you look at the copyright page, it shows Howden Buffalo as the publisher.

Some have observed that the book looks a bit like a bible;  the fact is that it is kind of the “bible” of fan physics and application.  Howden North America’s Fan Engineering handbook is somewhat of a classic in the industry.  The first copy I owned is from the early 1970’s;  I picked it up in a used book store at some point after coveting the copy one of my mentors had, which they generously allowed me to borrow. The copy in the picture is the 9th edition, published in 1999.  However, the book has its roots in work by Dr. Willis Carrier, and was first published in 1914.

I bring all of this up because I recently discovered that Howden has made it much easier to obtain a copy of the book.   Specifically, if you follow the links on their web site, or simply click on this link, you will be take to an page where you can purchase new or used copies.


The only used copy offered on as I write this is going for $85, which is still a good deal considering the content.   But, I suspect you can find copies for less by shopping around a bit on the internet or used book stores.  For instance, I just found a copy of the 8th edition (1983) for $22.99 on the Alibris web site.  Since the principles behind Newtonian physics have not changed much since 1983, I suspect the used 1983 edition represents a good value for someone on a budget.

Having said that, read on as there are some advantages to getting the latest edition.  Interestingly enough, you will notice that the price range for a new copy, currently at least, is from $100 (directly from Howden) to $189 (from a reseller).  My thought is that unless the reseller has a copy signed by Willis Carrier, you’re probably better off ordering from Howden.

What’s not so obvious from the web site is that if you e-mail Howden at before ordering, you can specify your prefernce for an electronic copy of the handbook as a CD instead of the paper copy.  This alone may be worth the price of obtaining the latest copy for a number of reasons I discussed in a previous post, including portability, searchability, physical storage space and weight (especially when traveling), and sustainability.  But, the electronic version of the Fan Engineering Handbook complements all of these features by including interactive content.

Here is a screen shot of the table of contents, which is the starting point for using the electronic version and also illustrates the wealth of information available in the handbook  (both electronic and paper copies).


Clicking on the highlighted topic Fan Testing takes you to the content of the chapter.


Clicking on the hyperlink for the chapter takes you to a bookmarked summary of the chapter content, from which you can jump to the topic of interest.



You’re probably thinking “that’s all nice and everything, but every well structured electronic document does this sort of thing”.  And while that’s true, the electronic version of Fan Engineering has done a very thorough job of it by providing hyperlinks that take you to related relevant content elsewhere in the handbook.  For instance, in the actual handbook, clicking on the equation hyperlinks shown in blue above will take you to those equations, which are in a different chapter.

But better still, the manual includes spreadsheets pertinent to the various topics discussed.  For instance, if while working with the electronic version of the handbook, you click on the little calculator/spreadsheet icon illustrated in the screen shot above, the following Excel spreadsheet opens up.


This is a spreadsheet that assesses flow rate based field data from a pitot tube traverse.  Note that it is set up for both IP (U.S.) and SI (metric) units.  If you wonder exactly how to use it, you just page down a bit.


If you are wondering exactly how the calculations are done, you can simply highlight a cell, and view the formula, just like you can in any other Excel spreadsheet.


If you wonder what some of the “funny” symbols mean, then just use the electronic table of contents to jump to the Appendix of Symbols and Abbreviations


… or use the hyperlinks or .pdf search function to jump to one of the referenced equations (click on the binoculars or press“Ctrl” and “F” together to get a little search window where you can type in what you are looking for).


One word of caution;  as near as I can tell, the spreadsheets are not protected.  In other words, you should save a copy to your project directory using the “Save As” feature of Excel before you modify them or add values.  Otherwise, when you select “Save”, you will over-wright the original spreadsheets in the Fan Engineering directory.  That’s probably not the end of the world, but if you needed a clean copy, I suspect you would have to uninstall and then re-install the CD content.

For me, the electronic version of the CD is well worth the cost (it’s $149 vs. $100 for the paper copy).  And, truth be told, I really appreciate having both the electronic and paper copy.  Obviously, the electronic copy is handy for my field work and teaching.  But for me, there is some sentimental attachment associated with the paper copy; its like having a bit of a tangible connection with one of the founders of our industry.  And some of the affection for the paper copy is my age;  I grew up with paper books and while I have a Kindle Fire, which is wonderful for traveling and in low light conditions and for its functionality beyond just being an e-reader, I still like the feel of a book in my hand as I read it.

As you probably have noted, this is not a free resource, like many of the ones I list in the reading and resources list I posted previously.  But as I have indicated, it’s a classic reference and a valuable resource for anyone involved with HVAC as a profession and well worth the money.  And, there is some good news if you are a student.  Howden offers a $75 student discount on either the CD or the paper copy of the handbook.  To see if you qualify, simply send an e-mail to asking for more information.  I’m sure you’ll get a speedy reply.

So, many thanks to Howden North America for making this resource available and for making it easier for students to obtain a copy of the latest and greatest information on fan engineering from the pens of leaders in the industry.

David Sellers
Senior Engineer – Facility Dynamics Engineering

Posted in Air Handling Systems, Resource List and other Resources | 2 Comments

Pneumatic Controls Resources

Author’s Note: I originally published this post on March 3, 2013.  At that time, all of the resources I mention below were loaded up in “the cloud” on a Google Drive.  Since that time, I have created the commissioning resources website to complement the blog, which makes it much easier to distribute information like this and maintain it.  So, I have moved these resources to that location, specifically, to a page I have created for them under the General Resources page.

I have also added a little silent movie that starts with pictures of various types of pneumatic control hardware that I have taken on various existing building commissioning projects.  That is followed by a set of animations that illustrate how one and two pipe pneumatic controls work.   The video concludes with some slides summarizing the pros and cons of pneumatic control and actuation along with some bottom lines about pneumatic control.

The information in this blog post is still relevant and will provide additional insight into pneumatic control and what is included in the resources, so you if you are new to pneumatic controls, you may find it helpful, along with the post that preceded it titled Pneumatic Controls, First Cost Advantages, and Retrocommissioning Opportunities.


Since the post I recently put up on pneumatic controls (actually even before I did that), people occasionally ask me if there are resources out there that would help them better understand pneumatic controls.  Even though the industry is moving to direct digital control as “business as usual”, if you are working in existing buildings, you will still find yourself confronted with pneumatic control technology.  As a matter of fact, we just ran into a bunch of it during two field classes in the Existing Building Commissioning Workshop Series that I do with Ryan Stroupe  at the Pacific Energy Center (see page two of the linked brochure if you are interested).

Here is a picture of a pneumatic control panel that is currently operating a system in Post Montgomery Center, a large high-rise in downtown San Francisco.

Executive Floor Receiver Controller Panel

Erik Carlson, chief engineer for the facility, currently is working through the building and upgrading panels like this to DDC.  But meanwhile, the operating team needs to keep the existing pneumatics in top form to maintain their LEED Gold status.

Across the Bay on the Berkeley campus, we ran into this pneumatic control panel which had been retained and piped through manual valves to back-up the retrofitted DDC control system serving the facility.

Pneumatic Controls

In this picture, you can see the pneumatic lines from the old control panel coming together through small, manual, isolation valves with the pneumatic lines from the electro-pneumatic circuit boards in the panel to the left (the valves are the small “T” shaped devices right above the panel to the left and in the lines above the panel on the right side, which is the pneumatic control panel in the picture above with the door closed).

Pneumatic to Barrington Valves 01

Here is a close-up of the circuit boards in the panel to the left in the picture above. 

Pneumatic Interface

Basically, the boards respond to signals from the DDC control system to pulse air into or out of the line to the device they control. In the close-up of a typical board below, you can see the main air (nominal 25 psig supply air) coming into the board via the black tube and connecting to a manifold. 

Pneumatic Interface Close Up

Two small solenoid valves (the shiny cylinders mounted on the black cube, which is the manifold) are pulsed by signals from the DDC system. 

Pulsing one valve causes it to open and allow main air to flow into the output line (the yellowish tube with the gauge in it).  Pulsing the other one allows it to bleed air out of the output line.  These short, digital (on-off) signals work together to create the analog (continuously variable) air pressure output from the system that is used to position the final control element, which in this case, is a steam valve.

The bottom line is that to work on existing buildings (both now and for the foreseeable future near as I can tell) you probably need to have a working knowledge of pneumatic controls and some resources. 

Unfortunately, a lot of the really great resources I had available to me when I was learning this stuff  are no longer readily available.  That’s because many of them were mentors who have retired, or in some cases, passed on.   Others are printed materials that seem to have been supplanted by new information on the new technologies. 

So, in an effort to honor the knowledge that was shared with me by the people, and to make the printed information I have available for others, I decided to scan some of my more useful resources and post them on my Google Drive so you can access them if you would like.

This is likely a violation of some sort of copy-right law, and if someone from one of the companies whose literature I have scanned contacts me and tells me to “cease and desist” with my effort, I will have to pull them back off.  But I suspect that will not happen since much of this is from the 1960’s and 1970’s and most people consider the information it contains to be obsolete.

In fact, when I contacted one of the majors a while back to see if they would allow us to post their damper and valve sizing engineering bulletins as .pdfs on the California Commissioning Collaborative web site (I was with PECI back then) they not only said yes, the guy I was talking to asked me to forward copies to him too since they sounded really useful and he could no longer find the originals. 

I still had mine because I kept my application engineering manuals from when I had worked for them.  In the interim, the company had been sold several times and the various documentation and engineering resources were “cleaned up and made current” by the new owners, I guess.

Having said all of that, what follows is a listing of the documents I have put up along with a link to them and a description of what they are about and why I think they are useful.  There is also a link to the folder containing them in the resource links on the home page of the blog.

The Honeywell Gray Manual

This is the one resource on the list that is not on my Google Drive.  That is because you can download it from another location on the web.  I link to it and discuss the “Gray Manual” in a previous post on the topic.  The bottom line is that it contains useful information on a number of aspects of HVAC including chapters on all of the common control technologies, information on HVAC fundamentals, psychrometrics, and common HVAC system types, all presented in a very straightforward, understandable manner.   It’s a great way for somebody new to the industry to gain an introduction to it and a valuable resource for someone who has been in it for a while and needs a “refresher” on a particular topic.

Johnson Controls (JCI) Fundamentals of Pneumatic Control

To be honest, one of the things I like the most about this particular document is more nostalgic than technical, that being the neatly printed signature and date of Phil Sutherlin across the top of the first page.


That’s pretty much how Phil printed all of the time, be it on a drawing that was going out the door or on the sketches and illustrations he made to help me learn things when I asked him questions. 

As a young engineer, I strove to emulate it as well as and the free hand drawing style he used to lay out systems during schematics and design development.  I actually got kind of good at it, and one of the things that bugs me about where technology has taken me is that since I type and click more and print and draw on paper less, I have lost a bit of that.

But I’m sidetracking a bit here.   Nostalgia aside, the value of this particular document is that it contains a lot of very practical information about control theory (meaning that it applies to any control technology) as well as how that theory is implemented in a pneumatic instrument.


JCI Pneumatic Controls O&M Manual

Some of the information in this document is similar  to the Pneumatic Fundamentals documents.  But the focus is more towards helping operators understand how to adjust and maintain the instruments.


There is even a section on replacement parts.  Believe I t or not, we used to actually fix technology when it broke instead of throwing it away in a landfill and buying a new one.  Perhaps a little lesson in sustainable operations there for us today.

MCC Powers Fundamentals of Pneumatic Controls

MCC Powers is now Siemens after going through a number of other owners in the process.  Their Engineering bulletin on pneumatic controls fundamentals is a nice complement to the information in the JCI Document.  While the JCI document includes some diagrams and a lot of pictures of the hardware, the MCC Powers document includes a lot of diagrams with explanations that illustrate how mechanical systems of diaphragms, levers, and springs were used to accomplish control processes like proportional control or floating control or PID.


Now, of course, we do all of this digitally with math.  But for me at least, seeing  and understanding how a mechanical device would accomplish the function was key to understanding how things worked, both then and now. 

I think that is true for a lot of people actually because the “float in a tank” analogy I use when I teach PID  control really seems to connect the dots for a lot of folks.  I know it did for me and it has its roots in some of the discussions in documents like this one.

MCC Powers and JCI Pneumatic Main Sizing Data

This document describes the process used to size the air mains along with related reference tables and sizing charts.   One of the hardest things to find these days is some sort of documentation on the air consumption of various control devices.  That can be useful information in an existing building commissioning process if you are trying to understand if a compressor is running more than it should due to leaks or if the demand from the control instrumentation is the cause.

Eventually, you can find out what you need to know, but you have to dig around a lot in the catalogs from various manufacturers.  And often, the specific device you are looking for is no longer manufactured.  Back when I did a lot of pneumatic control design, I had a table that listed most of the common devices from the MCC Powers product line along with their air consumption rate and I have scanned that table and included it in this set  of documents.


I have found that it is reasonable to assume similar devices from other manufacturers use air at about the same rate in the general case, even though the specific values probably vary from manufacturer to manufacturer and device to device.

In addition, even thought pneumatic controls are receding from the scene, pneumatic actuation is alive and well.  So having the ability to size air mains and compressors is still quite handy out there in the field.

One  note with regard to sizing systems for actuators;  when I first got into this, I was puzzled about why the table above did not include consumption rates for actuators.   It finally dawned on me that it was because unlike a pneumatic controller ,which constantly bleeds air to operate (the link takes you to some slides that illustrate this), pneumatic actuators only use air when they move.  And the volume they require to go full stroke is basically the diameter of the actuator cylinder times its stroke.

That means if you had a system that was only serving devices like actuators, then the size of the compressor and mains is more a function of how many actuators you think might move concurrently and how quickly you need them to move.  That means that you can often get away with a smaller compressor, especially if you complement it with a large storage tank, which can act as a sort of pneumatic flywheel.

MCC Powers RC 195 Receiver Controller System

For me at least, one of the best ways to understand something is to immerse myself in the details of how it works.  This document will allow you to do that for an RC 195, which is the MCC Powers (now Siemens) receiver controller.   This device is still available and in use out there  In fact, the controllers in the Post Montgomery panel at the beginning of this post are RC 195s. 

RC 195 Close Up

The controllers in the UC Berkeley Facility control panel are similar devices but manufactured by Honeywell.

The fundamental difference between a receiver controller and a controller that has the sensor built into it, like the remote bulb controller illustrated below, is that instead of using a sensing element that measured a specific parameter, like temperature, which was an integral part of the controller, receiver controllers were set up to use a 3-15 psig pneumatic input.

image  image

Pneumatic Controller 01   Pneumatic controller 05

In the pictures, the upper row are taken from the JCI Operating Manual and show the parts and a cross section of a controller very similar to the one in the photographs below.  In the photo at the lower left, you can just see the bellows that is part of the temperature sensing assembly (the silver cap shape behind the plate with screws) that shows up connected to the thermal sensor in the illustration above.

Returning to the receiver controller discussion, by using a generic 3-15 psi pneumatic input, receiver controllers could be interfaced with pneumatic transmitters that were designed to measure a number of different HVAC parameters like temperature or humidity or pressure. 

The transmitters generated a signal that varied from 3-15 psi as the parameter they measured varied over a given span like 0-100°F.  They are identical in concept to the 4-20 ma, 1-5 vdc, and 2-10 vdc transmitters we use today with DDC systems.   They just used air pressure to transmit the information instead of electrons. 

If you understand one technology, you can easily understand the other, which is a topic I discuss in an article I wrote for HPAC magazine a while back called Analog Lessons for a Digital World, along with other things I learned working on pneumatic controls but apply every day while working with DDC controls. My bet is the “cross training” works the other way too; i.e. if you understand DDC control fundamentals, you can readily transition to pneumatics once you learn the jargon and hardware.

Here is a picture of a one-pipe temperature transmitter that is piped to one of the controllers in the panel at UC Berkeley, illustrated at the beginning of the post.

One pipe transmitter 03

The generic input capability meant that only one controller design was required and you adapted it to the HVAC process by virtue of the transmitter you selected.

Bottom line is that the RC195 documentation will allow you to get into the details of how one works and how to use it.  In addition, it has been my experience that once you understand a specific device, the knowledge is easily transferred to similar technologies from other manufacturers.

Fisher Process Grade Pneumatic Controllers and MCC Powers Series 200

If you really want to see how a remote bulb type controller works, the product bulletins for these process grade controllers will give you a pretty good picture of that.  Incidentally, the MCC Powers Series 200 controller is the controller that shows up in the pictures in the photo gallery in the post titled Retrocommissioning Findings: Make Up Air Handling System Simultaneous Heating and Cooling – The Clues – #2 – The Controls May be Pneumatic.  

The instructions are hard to find;  I lost my copy when I moved to Portland and the box the the binder with all of my MCC Powers manuals was lost.  The copy I ‘m sharing here was graciously shared with me by Adam Lebavitz of M&M Control Service Inc.  M&M now owns the remaining stock and manufacturing rights to the Series 200, so if you are looking for parts or service on this type of equipment, they are the folks to talk to.

JCI Damper Engineering

One of the advantages of going back into your files and looking for something is that sometimes, you discover something useful that you forgot you had.  This is an example of that and comes from the JCI engineering manual that Phil gave me.

Among other things, this document contains actuating force and stroke data for a number of different actuator types,   including a technical discussion of the topic and a really cool little nomograph that helps you figure out the relationship between lever arm, stroke and angular rotation for a given arrangement.


When I bring this topic up, some folks say its not very useful information given that the industry is moving to centerline drive actuators and eliminating the linkage systems between the actuator and the damper.  Personally, I’m not so sure about that as illustrated by these recent field photographs.

OA Damper - Centerline actuator with Crank 01

Zone Dampers - Opposite End Zone Dampers - Actuator End

The upper photograph is an actuator serving one of a number of outdoor air damper sections in a large (200,000 cfm) economizer equipped AHU.  The lower pictures are from a triple deck multizone unit.  The actuators on the left control all three deck dampers through a menagerie of lever arms, springs, and shafts.  Here is a system diagram of the unit which will help you understand.


Interesting study in kinematics if nothing else.

Another interesting thing is the damper performance curves included towards the end.


I haven’t tried it yet, but I suspect you could manipulate this data into a version of the damper performance data that shows linearity vs. pressure drop that can be found in a number of places like the Honeywell Gray Manual and the MCC Powers Damper Sizing Bulletin I link to in the resources on the blog’s home page.


Granted, the information in this document pertains to older models.  But my bet is that geometric similarity and some engineering judgment would allow you to extrapolate this information to a current application.  That can be particularly useful if you don’t have any other information to work from.

JCI Reference Information

This is one of those collections of useful facts and figures that are handy to have around.  This particular documents includes things like:

  • units conversion constants,
  • basic HVAC and physics equations,
  • a steam table, 
  • tables with the relationship between wet bulb, dry bulb, dew point, and relative humidity,
  • velocity vs. velocity pressure tables,
  • properties of things like glycol and other anti-freeze solutions,
  • standard pneumatic control drawing symbols (well, the JCI standard anyway, which was a pretty good one actually and similar to the other manufacturers),
  • design conditions for a number of places (bear in mind this is probably mid 1960’s data), and
  • summary psychrometric process diagrams for typical HVAC processes.

The latter is one of the reasons I have included it since it is a quick way for someone new to the industry to start to understand what happens in some of our HVAC processes and correlate it with the psych chart.  For example, here is the one for a cooling coil that is doing dehumidification and cooling.


Well, that’s it.

Hope this is useful to some of you.  I know I have found the information to be useful over the course of my career, including the current time frame.

David Sellers
Senior Engineer – Facility Dynamics Engineering

Click here for a recent index to previous posts

Posted in Operations and Maintenance, Pneumatic Controls, Resource List and other Resources, Retrocommissioning Findings | Leave a comment

A Steam Heating Resources

I recently helped to present a class titled Steam and Hot Water Systems;  Design, Performance, and Commissioning Issues;  one in a series of classes I am involved with at the Pacific Energy Center.  Ryan and I have been trying to make the classes more interactive and flexible in terms of being able to address the interests of the people attending them.  As a result, I tend to try to develop and expand content based on the feedback from the last class.

So I always have plenty to present, probably more content available than I will have time to deliver.  So what I actually end up talking about is driven by where the interactive exercises take us, student questions, and lately,  what the students say they are hoping to learn about when I ask them at the beginning of the class.

So, point being that for the latest round of the Steam and Hot Water Systems class, I had added some content about low pressure, one pipe and two pipe comfort heating systems; basically, the type of system you might find in an older residence,  older multi-family housing facilities, older hotels, and older schools.  I pulled that together because the last time I presented the class, a number of the students had specific comments or questions about that type of system and at the time, I did not have much content developed for it;  the class was more focused on hot water than steam and more focused on larger commercial installations rather than residential installations (although physics being physics, the principles are all the same).

But as luck would have it, for the most recent class, the majority of the interest was on other topics so I never got around to presenting the new material.   Having said that, since steam heat is rapidly becoming a lost art (more on that in a minute) and there are some really good resources out there for those who are just learning about it, I thought I would go ahead and write a short blog post to connect you with those resources and some of the content I put together but didn’t use in the class.

 The Lost Art of Steam Heating

One of the best, if not the best resource out there for you if you are trying to understand or otherwise work with steam heating systems is a book by Dan Holohan titled, appropriately enough The Lost Art of Steam Heating.   I have a paperback copy of the original version and a Kindle copy of the revised version.    The gallery below, which is made from screenshots from my Kindle version will give you a sense of what the book is like.  Click on any image and it will open a slide show with larger images.

The book starts out with a bit of history, including pictures of some of the early steam heating equipment, and then moves on to describe how one and two pipe low pressure steam systems work in an very easy to understand, engaging manner.  Generally, if you understand a few basic principles, like stuff will move from where the pressure is high to where the pressure is low and how a manometer works, principles that are nicely explained in layman’s terms in the book, then you can understand how steam systems work.

The author’s website itself is full of resources that complement the book, including pictures and technical articles dedicated to heating systems, steam and otherwise.  If you are involved in this business at all, you definitely should have it saved in your list of favorites.  And you probably will want and will enjoy a copy of the book.

Bill Coad on Steam

As you probably know if you follow my blog, one of my mentors was Bill Coad.   Bill did a lot of technical writing over the course of his career and one of the things he wrote about was steam.

There were a number of his Fundamentals to Frontier’s columns that covered the topic and several chapters in his energy engineering book that included content about steam.  In addition, he wrote a fairly extensive article for Heating, Piping, and Air Conditioning magazine on the fundamentals of steam heating.

All of those things are getting harder and harder to find on the internet since some would consider them dated, having been written in the 70’s, 80’s and 90’s and this being a different century and all of that.  But since Bill always wrote about things from a fundamentals level, and since Newtonian physics still seems to be a good model for what is going on around us (I just checked by dropping a pencil and it in fact accelerated towards the floor of my office and then stopped upon encountering the floor), the content is generally timeless and thus they are valuable resources.

To facilitate your ability to access them, I have created a Bill Coad’s Writings page on my website and have all of the resources I mentioned above accessible for download from that location.

A Typical One Pipe Steam Radiator

It just so happens that Hotel Carlton, the hotel I stay at when I am in San Francisco, has a one pipe steam heating system.

As an aside, I highly recommend it.   It’s a cool old building with really great people working in it in an interesting neighborhood;  you’ll really  feel at home right away I think.

That said, even if it didn’t have the steam heating system, it is a pretty cool place because it was one of the first buildings erected after the 1906 earthquake and its design was targeted at being earthquake and fire proof.

But, in the context of this blog post, it has a one pipe steam heating system and the system was recently upgraded to include self-contained radiator control valves.  Here is what one of the radiators looks like if you take the cover off of it (as I am sure most guests do once they realize they have an actual working one-pipe steam radiator in their room).

One pipe radiator with manual valve and self contained air vent type control valve 02

The pipe with the bronze valve is the “one pipe” serving the radiator, that allows steam to enter it and condensate to leave it.   If you think about that for a minute, you can start to see why the details of how you pipe and control a one pipe radiator might matter.

If you look at the other end of the radiator, you see this.

Self contained valve - air vent type

The silver gizmo is a type of air vent, and the gray thingy attached to it, along with the fitting it is mounted to, is a self contained control valve.  The little cable weaving away from it and up and to the right is the set point signal, which allows you to adjust the set point from a wall mounted controller, pictured below.

Self contained valve remote set point adjustment 02 This picture shows the entire control valve and set point adjustment in one picture.

Self contained valve remote set point adjustment 01

The general idea behind how this works is that steam, not air, even hot air, is what will warm up the room with a radiator in it.   If the radiator is full of air, it will not be full of steam and will not provide much if any heat.

The self contained valve basically allows air to exit the radiator, which means steam can enter it until the desired set point is achieved.   Then, it stops allowing the air out, which means it also stops letting the steam in.

Its a bit more complicated than that because of what happens to the pressure in the radiator as the steam condenses and things like that.  Dan Holohan does a great job of describing it in his book and this instructional PowerPoint from the Danfoss web site is also pretty good.

Danfoss is one of the manufacturers of self contained valves for radiators.  In fact a lot of the time, people in the industry will refer to any self contained radiator valve as a Danfoss valve even if it is one made by Watts or Honeywell or one of the other manufacturers in the bussiness.

Its sort of like calling all facial tissue Kleenex;  Kleenex is a brand of a type of product called “facial tissue”.  But they have been so successful in marketing their product that a lot of people equate “facial tissue” with “Kleenex”.  Same thing for “self contained radiator valves” and “Danfoss”.

Steam and the FDE Resource List

If you have a copy of the resource list on our website, you will find that there are a number of links to resources related to steam in it including links to the DOE tip sheets for steam systems, Wayne Kirsner’s web site, and the Armstrong International handbook to name a few.

I should mention that the links it contains to Bill Coad’s resources will no longer work.  But as I mentioned above, you can now find all of that information in the Bill Coad Writing’s page on our website.

So there you have it; a few resources for you to look into if you are trying to understand one of the oldest approaches out there for heating a building, an approach that can do a really nice job of it if you apply it properly.


David Sellers
Senior Engineer – Facility Dynamics Engineering

Posted in Boilers, Hot Water Systems, and Steam Systems, Resource List and other Resources | Leave a comment

Site versus Source Energy

Author’s Note:  I originally posted this in September of 2007 and used a report I had found at that time to develop some of the source energy factors I used in my illustration.   Since then, I have found a number of other resources on this topic which are more current and also provide more information.  I document the new resources in a footnote at the end of this post if you are interested in looking at them.

In my previous post, I mentioned that using an electric resistance coil to generate a btu of heat can be expensive relative to burning a fossil fuel on site for the same purpose because of the difference between site and source energy.

If one only considers energy crossing the site boundary and the conversion efficiency of the electric heating coil, electric resistance heat seems like a real winner. With a conversion efficiency of 100%, every kWh that runs through a resistance element provides 3.413 btu of heat to the facility.

In contrast, even the most efficient, current technology condensing boilers available with everything working just right can only deliver 95-98% of the energy that goes into them as heat to the facility. Conventional, non-condensing burners are lucky to achieve 85% efficiency and older equipment near the end of its useful life cycle may only have a combustion efficiency in the mid 60% range! So, why wouldn’t you want to use electric resistance heat and what makes it so expensive?

The answer to that question lies in the difference between site energy and source energy. There are a number of losses that occur between the point where a fossil fuel enters a power plant for conversion to electrical energy and the point where that electrical energy reaches the meter serving a given facility.

One of the most significant losses occurs in converting the fossil fuel to heat, the heat to shaft power and the shaft power to electricity. In general terms these losses are associated with combustion efficiency, losses through insulated piping systems, the irreversibility associated with the thermal cycle of a turbine, and mechanical and electrical losses in the turbine and generator (bearing friction, less than perfect conductors, less than perfect magnetic materials, aerodynamic losses associated with shafts and armatures spinning in air, etc.).

The Energy Information Administration tracks the heat rate for electric generation in a number of publications including their Monthly Energy Review. The graph below plots this data from 1946 through the current year (data for the current year is an estimate).

Note that in general terms, it takes about 3 btus into the generating system to produce 1 btu of electricity.

But wait, there’s more! It takes power to make power. Depending on the exact nature of the facility, the power plant will need to run forced draft fans, induced draft fans, feed water pumps, deaerators, cooling towers, condenser pumps, soot blowers, air compressors, control systems, cooling systems, lighting systems, and life safety systems, to name a few possibilities. All of these systems require power and impact the amount of energy that needs to go into the plant to make the electricity that shows up at your meter.

There are also losses in the transmission and distribution process. Generally, we think of copper and aluminum as being good conductors with virtually no losses associated with the current flowing through them. But if you run current through miles or even hundreds of miles of copper or aluminum wire the over-all resistance adds up.

If you do the math, power is lost as a function of the square of the current multiplied by the resistance it is flowing through. To minimize these “I squared R” losses, we transmit our electrical power at high voltages. But, since the electric and magnetic circuits in our transformers are not perfect, we also experience losses at that point in the distribution process. And since the high voltages used to distribute and transmit power make it very dangerous to be around, we step the voltage back down at the other end of the distribution system, incurring another loss.

The Department of Energy, Office of Energy Management estimates transmission and distribution losses to be in the range of 8%. In a 1995 report titled Measuring Energy Efficiency in the United States’ Economy, factors were developed to take all of these variables into effect on a regional basis (see footnote 1). These factors are depicted in the graph below.

A number of reporting agencies like CBECS apply these factors to their site energy consumption figures to assess the source or primary energy required at the power plant to produce the site energy.

To make this graph directly comparable to the heat rate graph, I multiplied the conversion factors by 3,413 btu/kWH.

The bottom line is that only 30-40% of the energy that enters a power plant as a fossil fuel shows up at your electric meter as electricity. Worse yet, short of resistance heaters, very few of the devices that use that electricity once it reaches the meter are 100% efficient.

For instance, a 1,200 gpm chilled water pump with a 25 hp motor might have 8-10% of its incoming power lost in the motor and another 15-20% lost in the pump itself.

If the site energy graph for the lab facility I have been discussing is converted to source energy using the 1992 Western Region conversion factor published in the 1995 report I mentioned, it reveals that while converting to boilers from heat pumps increased the site energy consumption, it decreased the source energy consumption.

So, the planet won, even though the Owner’s pocket book didn’t.  Had the original electric heat been resistance elements instead of heat pumps, the difference would have been even more significant.

The bottom line is that if you are going to burn fossil fuel to make heat, you are frequently a lot better off burning it on site rather than burning it at a power plant to make heat to generate electricity which you then convert back to heat, at least from the standpoint of the environment and conservation of non-renewable resources.

The big hit to your pocketbook typically associated with electric heat only begins to reflect the big hit to the non-renewable resources and environment that electric heat represents when it is served from a fossil fuel burning power plant.

David Sellers
Senior Engineer – Facility Dynamics Engineering

Footnote 1, 2017-06-30

Energy Star Portfolio Manager has a technical reference titled Source Energy, which publishes and discusses the factors they use in their projections.

In 2007, the National Renewable Energy Laboratory (NREL) updated a technical report NREL/TP-550-38617 titled Source Energy and Emission Factors for Energy Use in Buildings that documents the factors for electricity and fuels delivered to a facility and combustion of fuels at a facility at a regional level.  It also includes links to other references.

Emissions & Generation Resource Integrated Database (eGRID) periodically publishes a database in the form of a spreadsheet that covers just about all of the electrical power generated in the United States, including emissions, net generation and resource mix.  The spreadsheet lets you filter it in many ways.  The table below is an example of one I made to look at the resource mix on a state by state basis.


Posted in HVAC Calculations, HVAC Fundamentals, Resource List and other Resources | 2 Comments