How to Read HVAC Drawings 5: Section, Schematic & Elevation


I learned to read different kinds of HVAC drawings through years of working in the HVAC industry. I thought if junior engineers are able to know how to read HVAC drawings earlier, they are able to come out with a better HVAC system. So, I decided to create a course with a series of posts to explain how to read HVAC drawings.

In this course, I have 5 posts on how to read HVAC drawings. These 5 posts are:

  1. Title block & symbols
  2. Ventilation system
  3. Air conditioning system
  4. Control panel diagram
  5. Section, schematic & elevation drawings
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In this post, you’ll learn about section drawings and schematic drawings. These drawings are different from typical layout drawings and they serve different purposes. They usually have more details derived from the respective layout drawing.

Section Drawings

Layout drawings are difficult to present height which is a very important metric in construction. Furthermore, riser/dropper pipes and ducts are impossible to visualize in layout drawings. Hence, section drawings are needed.

A section drawing starts in a layout drawing by slicing through a particular area in the layout drawing to represent the view of the section drawing. Then, readers need to refer to a separate drawing to see the side view of that particular area.

A section cut on a layout drawing

To give you an example, the above drawing shows that a section is cut through a building. Usually, such a section drawing is labeled as “Section 2-2”. The symbol used for the section cut is a number or an alphabet inside a circle attached to a filled triangle pointing towards the view of the section.

A section cut can be just one symbol but it's much better to have two symbols stretching across the section view that you wish to present in a separate section drawing. Sometimes, small section views can be presented in a corner of the same layout drawing.

The line connecting the two symbols can be a solid line or dotted line depending on your preference. I prefer to use a solid line and I usually draw the symbol sort of like an eye because it looks better.

Gridlines

In a section drawing, gridlines are advisable to include if the section cut is substantial. For example, if you are cutting through a building or the entire chiller plant room, you should include gridlines for readers to understand easier.

A section drawing of a building

Sometimes, a section view can have many different structures and equipment. Maintaining gridlines in section drawings helps people to read faster.

Section drawings follow the same principle as layout drawings. Things drawn in a section drawing must be scaled. Section drawings are considered as detail drawings where workers are used for construction. In addition, section drawings should have dimensions clearly indicated.

Section Drawings within a Section Drawing

A section drawing within a section drawing can be done when a particular work is very complicated. Although it is generally better to have fewer section drawings, complex works are often better to show in separate section views so that people can read each section drawing better.

Section drawings within a section drawing

In the above example, it is impossible to show every detail in one section drawing. Thus, section drawings within a section drawing are necessary to present all information. The above section drawing is one of the section drawings that I previously worked on together with other engineers. It's a basement smoke extraction shaft.

Differentiate Section and Schematic Drawings

Not all side views are section drawings. Generally, section drawings should be scaled. On the other hand, schematic drawings are not scaled and are often used to illustrate the components of a system. Because there are so many components involved, put everything to scale in a schematic drawing is not practical.

Side view of a schematic drawing

Some people may consider the above drawing as a section drawing but I consider it as the side view of a schematic drawing. It posses the characteristic of a schematic drawing which is drawn in single-line and not-to-scale.

Schematic Drawings

Schematic drawings are used to illustrate the design aspect of a system rather than using them for installation works. While layout and section drawings are used by workers, schematic drawings are mostly used by engineers.

Most of the things drawn in a schematic drawing are presented in single-line and not-to-scale in order to fit in as much information as possible. Riser/dropper pipes and ducts are two major HVAC systems that will always have a schematic drawing.

Schematic drawings are also best to represent how the system works. A chilled water HVAC system can quickly become overwhelming to an engineer who is trying to understand it on 20-30 pages of layout drawings. However, by looking at 2-3 pages of schematic drawings, the engineer is able to understand the entire system relatively faster.

Sometimes, a schematic drawing can help us to understand the building height since most schematic drawings included the floor-to-floor height and floor levels. However, a better representation of a building's appearance and height is elevation drawings.

Elevation Drawings

Many people confuse elevation drawings with section drawings. An elevation drawing can have a side view just like a section drawing but the elevation drawing doesn't cut through half way. Elevation drawings show the outer appearance and dimension of a building.

A left elevation of a factory

Elevation drawings are seldom used by HVAC engineers. Some HVAC engineers don't even know such drawings existed. When designing the location for outdoor units, elevation drawings are very handy.

If you want to see more elevation drawing examples, refer to your house sales and purchase agreement where you'll find the front, back, left and right elevations of your landed house.

Conclusion

There is a lot more to HVAC drawings. HVAC drawings are presented with many different symbols and shapes. However, if you read enough of them, you'll start to see they are more or less governed by the same principle.

To recall the entire course on how to read HVAC drawings, we started with the title block and symbols. Next, we discussed ducts, grilles, airflow and fan specifications in course 2 about the HVAC ventilation system.

In course 3, we also talked about ducts, grilles, airflow but for the air conditioning system instead. Besides, we also included VAVs and duct internal insulation in the course.

Then, we open up HVAC control panels and discussed all of the electrical components in course 4. Finally, we end the course with different types of drawings including section, schematic and elevation drawings.

I hope you learn something from these 5 courses. Although not much, these are the things that I wish I know in the beginning as a junior engineer. With that, I believe you are a better engineer now and I look forward to your success story.


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