Building Hydronic Systems — Pressure Profile — For HVAC Project Managers

This post is in 2 parts.

Part-1 we deal with the theory.  The basic Hydrostatic equation and the Bernoulli’s equation.

I have used the customary US engineering units throughout.  This is mostly because almost all texts these days have a detailed SI units treatment of these equations and very little or none in IP units.

This is a big disadvantage for young engineers joining the HVAC field.  Hopefully this will help.


Building Hydronic Pressure Profile Part-1

Building Hydronic Pressure Profile Part-2




Psychrometric Concepts for HVAC Project Managers Part-1B

This is where I discuss the concept of VAPOR PRESSURE in detail.   Vapor Pressure is without any doubt the most important psychrometric property that needs to be understood for the HVAC engineer trying to learn psychrometrics.  It is bizarre that many students are going through “Psychrometric Chart”  training without even talking about Vapor Pressure.  The fact that ASHRAE chose not to show this property on their standard chart may have something to do with this trend.  You can “draw process lines” on the charts without any mention of Vapor Pressure but the penalty you pay is a loss of key underlying psychrometric concepts.

As usual conversion from PowerPoint to PDF and no narration leaves out a lot.  But I think the following will still be very helpful to new engineers.

Please send in your comments and corrections to me.  Thank you.

Psychrometry Part1-B

Psychrometric Concepts for HVAC Project Managers Part-1A

This post is the first in a series of 4 (maybe more) PowerPoint presentations that I am doing for my Company engineers about Pschrometry.

Without the benefit of narration it loses some of its usefulness.  But I still think it can be very useful for anyone in the HVAC field trying to learn the subject for the first time.

Note that on the top left corner there is a little notes button that has some more comments on the slide.


fachgesprach-5 1A

Pump Cavitation – A look Under The Hood

The original talk on this topic was a Power Point presentation.  The PDF attached does not have the benefit of the verbal commentary along with the slides.But it still conveys some key concepts and should prove useful.  (There is some “inside” humor sprinkled around, as the original was intended for my own Company Project Engineers – please ignore.)


Pump Cavitation NPSH

PID Control Concepts – Without Calculus! — Part – 2 INTEGRAL

Here is Part-2, which describes the “Integral” component of the PID control.  Some diagrams need a little work, and will be updated a little later.

Please open the pdf below and then come back here for comments:

20140301CHAPTER-4 integral

PID Control Concepts – Without Calculus! — Part – 1

I wrote this booklet in the middle 80’s when pneumatic controls ruled in the HVAC Industry and DDC was just beginning to appear.  (We were all fascinated with what can be done with a microprocessor based control with 16k bytes of memory!)  Although the content is a little dated, I still think it should serve very useful for people trying to figure out just what a PID controller does and how it is different from a straight Proportional only controller.

I will post this booklet in 3 parts: Part-1 Introduction and Proportional.  Part-2 Integral.  Part-3 Derivative.

I hope you find it useful.  Please click on the PDF link below and then come back here for your comments.


The Curious Definition of “Fan Static Pressure” Part-1

Many HVAC engineers work their entire careers and retire without realizing that what they always thought of as Fan Static Pressure is not how ASHRAE, AMCA or the fan manufacturer’s define Fan Static Pressure (FSP). The concept of Fan Static Pressure is a purely “defined” one – there is no direct measurement in the field that corresponds to “Fan Static Pressure”. FSP is commonly confused by Engineers with the Fan Static Pressure Rise or Duct Static Pressure Rise.

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Duct System Losses Are Total Pressure Losses

Confusion in the use of the terms STATIC PRESSURE and TOTAL PRESSURE is widely prevalent among HVAC Engineers and Contractors. There are serious consequences of not distinguishing clearly between the two, and one example would be that you make troubleshooting more difficult and in some cases impossible.

This article clarifies the distinction between Static Pressure and Total Pressure.

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A Closer Look At Condensing Boiler Efficiency PART-I

Mat Ansari PE

The art of peddling Boilers has shifted from the realms of Logic and Thermodynamics to sheer magic and out-of-context truths.  It is becoming imperative for Engineers like myself, who get involved with selecting Boilers maybe four or five times a year, to educate ourselves about the basic facts of boiler efficiency.  In this series of posts we will take a closer look at the work-horse of our industry – the common commercial gas fired hot water boiler in the 2 million BTU input range.  The posts will attempt to investigate the realistic level of efficiencies that might be expected from these boilers. We will assume that no special “heat recovery” contraptions are in use.

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