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Author Archives: David Sellers
Developing a System Diagram in the Field
Well, its been a while since I have posted (I say that a lot I realize). But I have been using my free time to understand how to use an application called 3DVista to create ways for folks to learn … Continue reading
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Training Opportunities
This is just a short post to let you know that I have updated the Training Opportunities page on the Commissioning Resources website so that it is current, including links to the classes I help support, may of which are … Continue reading
PID Loop Tuning and Aliasing
In the past, I have discussed the topic of aliasing; i.e. how looking at trend data where the sampling rate is to slow to capture what is really going on can mislead you. Yesterday, in the course of a class … Continue reading
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System Diagramming Resources
Those of you who know me or follow this blog know that I am a big advocate for applying the system concept and developing and using system diagrams for design, diagnostic and operational purposes. It is a concept I was … Continue reading
Energy Loss from a Run of Pipe
One of the folks in a class series I am helping with ask a really good question about the temperature drop they were observing in a run of pipe and its implications in terms of energy. Answering it involves applying … Continue reading
Some Psychrometric Self Study Resources
A while back, I wrote a blog post titled A Free Electronic Psych Chart and How to Use It to Plot Basic HVAC Processes. I use that tool frequently for the classes I help support and recently, with support from … Continue reading
An Interesting Psychrometric Process
2022-10-04 – Author’s note: In reviewing this post yesterday to answer a question that came up, I discovered that some of the psych chart images had their quality degraded for some reason. So, I have replaced them and I believe … Continue reading
The Perfect Economizer–Part 1–Laying Some Groundwork
An amazingly long time ago, I started a string of blog posts about economizers, that included posts about: Mixed Air Plenum Stratification, which illustrates how stratified temperatures and velocities can be in a mixing chamber along with how dynamic the … Continue reading
Using a Formula to Adjust an Axis in Excel, Plus a Simultaneous Heating and Cooling Case Study
Author’s Note; 2022-02-01. I discovered that earlier today, when I thought I had saved this post, planning to make some final additions, edits, and add a table of contents when I got back from my walk, what I actually did … Continue reading
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Happy Solstice
2021-12-26 – Authors’ Note: Yesterday, I realized that I had not fully taken into account how a pin hole camera works when I developed the SolarCan pictures. The image in a pinhole camera is upside down relative to reality. When … Continue reading
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A Field Perspective on Engineering 