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HVAC Mechanical Drawings

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HVAC Mechanical Drawings

Chapter #4 – HVAC Mechanical Drawings

The mechanical drawings we will be dealing with are specifically related to the HVAC industry. Just like the other trades, the mechanical drawings have a specific purpose to their layout, so as to communicate the requirements of the project.

Typical drawings found in the HVAC Mechanical set of drawings could include some or all of the following;

  • Legend
  • Abbreviations and symbols
  • Equipment Schedule
  • General Notes
  • Specifications
  • Zoning plan
  • Demo
  • Floor Plan
  • Elevations
  • Section Views
  • Details
  • Schematics
  • P & ID Drawings
  • Control Diagrams

HVAC Mechanical Equipment Schedule

The HVAC equipment is shown on the Mechanical Equipment Schedule drawings. Here you will find the HVAC equipment such as Air Conditioners, Air Handlers, Fan Coil Units, Fans, Chillers, Cooling Towers, Pumps, Air Distribution, Expansion Tanks, Boilers, VFD’s (Variable Frequency Drives), Condensers and various other components of the HVAC system.

Mech Equip Schedule
Mechanical Equip Schedule

Zoning Map

This drawing shows how the HVAC zones are divided up. Each zone typically has its own controller or thermostat. You can see that the floor plan is separated with dashed lines indicating which areas or rooms share the same HVAC zone.

There are 20 zones on this zone map indicated as 4-1 through 4-20. These 20 HVAC zones could be served from one air handling unit. Each of the 20 zones can be served by a VAV (Variable Air Volume) terminal, that will vary the volume of air to the space based on the temperature of the room and the thermostat setting.

HVAC Zoning Layout Plan
HVAC Zoning Layout Plan

HVAC Floor Plan

The floor plan is a view from above, as if you were floating above the space.

This is where the sheet metal ductwork and HVAC Piping will be shown for each floor and area of the building. You might find that the HVAC Sheet Metal and the HVAC Piping are shown on separate drawings to allow for clarity and avoid having drawings that are congested and hard to read.

In addition to the floor plans for each floor in the building you will also have a Roof Plan that shows that portion of the HVAC system that is installed on the roof. Also, located on the plan view is a North arrow to provide building orientation (see plan view below for North arrow).

HVAC floor plan
HVAC Floor Plan

HVAC Detail Drawings

This drawing shows various HVAC details such as how equipment is supported, connected or provided with accessories.

HVAC Detail Drawings
HVAC Detail Drawings

HVAC Controls Drawing

Most commercial HVAC systems provide some aspect of controls automation, except for the most basic system that may just have stand-alone thermostats. Control system vary in their sophistication based on the owners need to monitor the system and the size of the HVAC system. Large central plants will often have some form of BAS (building automation system) that optimizes the energy usage and schedule of the system.

HVAC Control Drawings
HVAC Control Drawings

Plumbing Drawings

You may need to check the plumbing drawings to confirm if certain scope has been shown on those drawings. Engineers will often put the condensate piping from air conditioners on the plumbing drawings, or the gas piping for a Gas/Electric HVAC unit.

Plumbing Drawings
Plumbing Drawings

Since you are doing the Sheet Metal there might not be much if anything of your scope shown on the plumbing drawings except heater or boiler flues, but since you work for an HVAC company, it still falls under your company’s obligation to determine scope.

Plumbing HVAC Scope
Plumbing HVAC Scope

As shown in the above split image of the plumbing and HVAC drawings of the same area, the plumbing drawings have the gas piping that feeds the Gas Furnaces that are part of the HVAC scope of work. It’s important to clarify in your scope letter that you have excluded gas piping.

Structural Drawings

Looking at the structural drawings will sometimes provide you with information on supports for the mechanical equipment, ducts or piping. You can also determine how big the beams are and if there is enough room to possibly convert some of the more expensive rectangular ductwork into round duct.

Below is a small section of a structural drawings showing a large commercial buildings support beams. Just like other trades, the structural engineer uses means and methods to communicate information about the supports. The width and weight per foot of the beams are shown circled in red. The designation “W21 x 44”, means that the beam is 21 inches in depth and weights 44 pounds per foot. The “W24 x 55” is 24 inches in depth and weights 55 pounds per foot.

Structural Drawing
Structural Drawing

Demolition Drawings

When bidding on renovation projects there is a good chance that the existing HVAC system and ductwork will need to be removed or reworked. The engineer will provide a demolition drawing identifying which systems are to be removed or relocated. Typical anything with a hash mark through it will indicate an item to be removed, whether it’s a piece of equipment or a section of ductwork.

Drawing Revisions

When changes are made to drawings that have already been issued for bidding, the engineers will issue an addendum set of drawings for any updated changes made. These addendums usually cloud the areas on the drawings that have changed as indicated in the below image. In the image below the addendum is indicated as addendum #1 (see red circle around addendum symbol).

You would need to compare this addendum set to the original set of drawings to identify any changes that were made to the drawings. If you didn’t begin your takeoff or estimate on the previous set, then starting with this set of drawings would include the latest changes.

Several things to consider when working with an addendum set. First does the addendum set include a full set? Sometimes the engineer will only issue the drawings that have changes on them. This means that the addendum set may not be a full set. Check the list of drawings on the cover page or on the Architectural set. Be sure to identify all the drawings that you are bidding in your proposal.

Another thing to be aware of is that the engineers don’t always cloud the areas that have changed. This means that you will need to review the complete set for any changes that were made by the engineer but not clearly identified on the addendum set.

HVAC Floor Plans
HVAC Floor Plans

The drawing above also shows the equipment tags outlined by the blue squares. The first one is “RTU-1.1”, which stands for Rooftop Unit, but as can be seen in the drawing, this units is on the ground level. The next one is for “EF-1.3”, which is an Exhaust Fan.

Specifications on Drawings

Some engineers prefer to put their specifications on the drawings instead of issuing a book of specifications. Below is an example where the engineer put all of the specifications on the front page (M101).

Specification Drawings
Specification Drawings
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Now click the link below for Chapter #5 “Understanding HVAC Symbols” to get an overview of the road signs on the drawings that provide information in pictographs.

Plan | Elevation | Section Views and Details

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Plan | Elevation | Section Views and Details

Chapter #3 – Plan, Elevation, Section Views and Details

You will need to understand how to read a set of engineered drawings before you can begin any sort of material takeoff or communication with others. This section of the course will explain how to understand and read the various elements of an engineered set of drawings.

Plan Views

The plan view is where all the floor plans are shown including other areas such as the Roof Plan.

Floor Plans

Each floor in the building will have its own drawing, unless the floor is too large to fit onto one drawing then there will be more than one drawing per floor.  The floor plan shows all the rooms, doorways, windows, stairways, elevators and whatever the Architect believes is pertinent information for an understanding of the floor plan. The Architects as indicated below as identified the following on this floor plan;

  1. Column number
  2. Distance between columns
  3. Room designation and size of room in square feet (SF)
  4. Room information chart (Schedule) listing each room number and its corresponding square feet.
  5. Match line indicates that there is a continuation of this floor plan on another drawing.
Floor Plan
Floor Plan – Plan View

Roof Plan

The roof plan is important as this is where some of the mechanical equipment is located. Roof exhausters, cooling towers, pumps, boilers, intake hoods and other HVAC equipment can often be found on the roof.

Roof Plan
Roof Plan

Looking at the roof plan we can see the following on the plans as indicated by the red circles;

  1. HVAC Equipment
  2. Key Plan as explained below
  3. Key notes that help explain what’s on the roof plan.
  4. The North arrow. This indicates the buildings orientation to the north pole.
  5. The drawing scale in bar format. This allows for an easy scale verification using any scale.
  6. The description of the plan view, in this case it’s indicated as being a “Partial” roof plan. This would give you an indication that there is another part of the roof not shown here.

Key Plan

The key plan identifies the area of the building that is being shown on the current drawing. For buildings that are too large to fit on one drawing at the standard scale of 1/8” or 1/4”, than the building floor plan needs to be shown on several drawings with match lines drawn to indicate where the drawing has been demarcated into separate drawing areas.

Plan Elevation Question
Key Plan

As can be seen from the shape of the shaded black portion of the Key Plan below, and the shape of the floor plan it is referring to, they are the same. So the Key Plan is a mini representation of the shape of the floor plan and the portion of the floor plan that this particular drawing refers to.

Also, the below drawing is the continuation of the floor plan shown above. The Match Lines line up to create a complete floor of the building as indicated by the Key Plan.

Floor Plan as identified by Key Plan
Floor Plan as identified by Key Plan

Multiple Floors

You have to visualize how each floor relates to each other. This will help you see the HVAC air ducts an piping risers that travel from the roof to the basement. By using the column lines on one floor, you can find the exact same place on the floor above or below. The yellow highlighted dotted lines align up one floors corner to the nest floor.

Floor Plans Stacked
Floor Plans Stacked

Drawing, Section View & Detail References

It would be difficult to provide the details of more intricate construction assemblies on the same drawing of the floor plan. This is where the Detail and Section view references clear up and better show the components and finish of these areas.

Drawing References
Drawing and Section References

The symbol helps you find the detail or section that is being referenced by the symbol. As shown in the example above the detail or section can be found on drawing “A-9”, Detail or Section #1. The arrows indicate the direction that you would be looking toward. The detail or section view will show you what you would see if you were standing there looking at the building components.

Detail Reference
Detail Reference

Detail #2 is found on Architectural drawing A-9 as shown by the reference above. The purpose is to show in greater detail the area that is outlined. The dimension shown are in metric.

Section View

This Section View comes from a cut of the plan view above. A section view is different than an elevation view. A section view shows a cut of some portion of the building, while an elevation view shows what the building exterior looks like on what of its sides, such as the north side of the building.

Plan View Example #2
Plan View Example #2

Above is the first floor plan view of a small commercial building with a section cut referenced as “C”. See this section cut below under the Section View.

Section View #2
Section View #2

Below is a partial section view of one portion of the interior indicated as Section View #7, as shown on drawing #A-10.

Section View #7
Section View #7

Building Section View

This shows the total section of the building along the cut. These views will help you determine the length of riser ducts that traverse from one level to another.

Elevation View General Layout
Elevation View General Layout

Elevation View

The elevation view shows the outside of the building from every orientation (North, South, East & West).

Elevation View
Elevation View

Detail Section View

Detail View
Detail View

Detail Views

The detail view provides a look at the building components that make up the area of reference. Details are drawn at a larger scale than the general drawings allowing for a better look at the methods of construction. On Architectural drawings, details could include doors, windows, eaves, while on Mechanical drawings they may show details of hangers, fire dampers, coil connections, equipment trim, and sheet metal duct seams and joints.

Mechanical Detail
Mechanical Detail
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Now click the link below for Chapter #4 “HVAC Mechanical Drawings” to get an overview of these drawings.

Architectural Drawings

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Architectural Drawings

Chapter #2 – Architectural Drawings (How to Read Construction drawings)

You will need to understand how to read the Architectural drawings as they have information that can impact the cost of the Mechanical estimates. This section will cover some of the Architectural drawings and what to look for when bidding a Mechanical project. This section is not an extensive coverage of Architectural drawings, but is intended to provide you with the knowledge on what to look for when bidding the mechanical portion of the project.

Architectural Drawings

You should be able to understand how to read the basic information on the Architectural drawings as these drawings are the foundation upon which all the other trades are drawn. The Architect designs the building, while the structural engineer figures out how to support the design. The Architectural design set may include the following drawings.

  • Cover Sheet
  • General Notes, Drawing Index, Abbreviations, Code Info
  • Plot Plan (site plan)
  • Foundation Plan
  • Floor Framing Plan
  • Floor Plans
  • Roof Plans
  • Reflected Ceiling Plan
  • Window and Door Schedules
  • Wall Sections
  • Elevation Plan
  • Details and Section Views

Architectural Floor Plans

You can use the Architectural floor plans to identify the name and use of a room. The drawings will show the room layout with walls, doors and windows. Each room should be identified by a room number and room name.

If you’re not familiar with reading drawings then you’ll need to study the background carefully to discern the various ways in which building items are represented on the drawings. Just like in real life the first one or two letters of the room number will indicate the floor its located on, as in this example here all the room numbers begin with 1, so we can assume this is the first floor.

Drawing layout
Architectural Drawing layout

As can be seen in the above image of the bathroom area taken from the floor plan of an Architectural drawing, there are symbols for each of the bathroom fixture. We have highlighted all the walls in yellow to make it easier to see each room.

Reading a set of construction drawings requires that you learn basic drafting guidelines and the symbols used to convey meaning, much like a traffic sign tells you what to expect up ahead.

Reflected Ceiling Plan

The reflected ceiling plan shows you what type of ceiling is used in each room. Below is an example of a small portion of a building, showing the type of ceiling used. With each set of architectural drawings there will be a legend for the ceiling types used in the set. (See legend below)

Reflected Ceiling Plans
Reflected Ceiling Plans

The below reflected ceiling plan identifies the type of ceiling, light fixtures used and the height (yellow highlight) of the ceiling in each room. Looking at the reflected ceiling plan above you can also see that Supply (blue highlight) and Exhaust (green highlight) grills are shown on the ceiling in addition to the lights.

Reflected Ceiling Plan Legend Example
Reflected Ceiling Plan Legend Example

The HVAC system ductwork and air distribution grilles are overlaid on the reflected ceiling plan. By looking at the reflected ceiling plan below and the legend above you can identify the type of ceiling that each air distribution is set into.

For any volume damper hidden above a hard lid ceiling you will need a remote damper operator or an access panel to provide a means for adjusting the damper. The remote damper operator allows you to adjust the volume damper without needing to remove a piece of the ceiling (see Sheet Metal Specialties).

HVAC shown on Reflected Ceiling Plan
HVAC shown on Reflected Ceiling Plan

Fire Rated Corridors

In large commercial buildings you will often find that the corridors are fire rated to protect the occupants in case of a fire. There are several common methods of rating the emergency exit ways. Fire rated corridors are important to the HVAC industry because under certain circumstances when a supply, return or exhaust duct penetrates the fire rated assembly, which could be the wall or ceiling, a fire or fire/smoke damper could be required.

Fire Rated Corridors
Fire Rated Corridors

The corridor or emergency pathways are rated to allow sufficient time for the occupants to evacuate the building in the case of a fire. The rated corridor or pathway will prevent the fire from spreading long enough for the occupants to get out. The area shown in red above is the emergency pathway or corridor that is fire rated.

Fire Rated – Slab to Slab System

In this method of fire rating the exit way, the use of rated walls extending from the floor all the way to the deck above provide protection. There is no rated ceiling, as the deck above is considered a fire barrier.

Fire rated walls - slab to slab
Fire rated walls – slab to slab

Fire Rated – Tunnel System

This version of a fire rated exit way is constructed in a tunnel configuration that’s fire rated for the purpose of protecting the occupants during an emergency situation. With the tunnel rated system if you penetrate the rated tunnel ceiling to install a supply, return or exhaust grille you will be required to install a fire damper or a fire/smoke damper to maintain the fire rated construction.

Fire Rated Tunnel Corridor System
Fire Rated Tunnel Corridor System

Here are the two most common fire rated construction methods side by side for comparison.

Fire Rated Construction Types
Fire Rated Construction Types

Detail Drawings

In order to show how certain aspects of the construction is to be built in greater detail each trade will provide a detail drawing. These drawings show various components of construction in greater detail. This allows the installers a more accurate detail of what the engineer expects in the way of material and methods in a visual format as opposed to the specifications.

Architectural Sheet Test-Question
Architectural Detail Drawing
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Now click the link below for Chapter #3 “Plan, Elevation, Section Views and Details” to get an overview of these drawings.

General Layout of Construction Drawings

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General Layout of Construction Drawings

Chapter #1 – General Layout of Construction Drawings

Reading a set of construction drawings requires that you learn basic drafting guidelines and the symbols that are used to convey meaning, much like a traffic sign tells you what to expect up ahead. The larger and more complex the project, the more drawings will be contained within the set. All the drawings together will provide for a fully constructed project, covering everything from the structure to the mechanical systems.

Reading Construction Drawings

In this first chapter we will cover how to interpret the meaning of the various lines, references, sections and the general layout of construction drawings.

Drawing List could include the following Trade Drawings;

  • Cover Sheet
  • Index
  • “G” General
  • “C” Civil
    • Roads
    • Parking
    • Site Utilities
    • Grading Plan
  • “L” Landscape
  • “A” – Architectural
  • “S” – Structural
  • “M” – Mechanical
    • HVAC Sheet Metal
    • HVAC Piping
  • “E” – Electrical
    • Power
    • Lighting
  • “P” – Plumbing
  • “FP” – Fire Protection
General Drawing
General Drawing Layout

Title Block

The main purpose of the title block is to identify the project and engineers involved in the design. Also included is a place for the individual responsible for the design and a date; a place to record the progression and date of any milestones such as a plan check set, addendums and their date. Title blocks can run horizontally along the bottom of the page or vertically along the right edge of the drawing. The title block should be visible when the drawings are rolled up, that way you can tell without having to unroll them which project it is related to.

Drawing Cover Layout
Drawing Cover Layout

Revision Block will show any changes made to the drawings since they were issued. You might also find the original issue date and comments such as “Issued for Construction”. A revision number will be given that corresponds to clouded areas on the drawing where changes were made under this revision number.

Grading plan – shows the new and existing grading, the contour of the land.

Location map shows where the property is located on a Google map or other source.

Key Plan – this shows you where in the building the current drawing is located in reference to other sections of the building.

Site Plan (Plot Plan) – this shows how the building structure is situated on the plot of land it’s built upon. The site plan shows the contours, boundaries, roads, utilities, trees, structures, and other significant physical features on or near the construction site. It shows the locations of proposed structures in outline.

The site planshows the survey marks, including the bench mark (BM), with the elevations and the grading requirements. Surveyors use the plot plan shown below to set up the corners and perimeter of the building using batter boards and the line stakes. The plot plan furnishes the essential data for laying out the building.

The yellow lines highlighted in the image below shows the property line, while the blue highlighted area shows the building area as it’s located on the property.

There will be a north arrow somewhere on the drawing providing the orientation of the building to North, this is especially important when doing heating and cooling loads. Depending on which hemisphere you’re in, this will determine which exposure get shade and how the sun hits various aspects of the structure, effecting its heat gain or loss. The north arrow is shown in the upper right hand corner of the below drawing.

The site plan is drawn at a small scale so that everything fits on one page including the property boundaries. As you can see in the example site plan below, the driveway is shown entering off of the roadway. A dimension is shown indicating how far each corner of the building is in relationship to the property line or boundary.

Site / Plot Plan
Site / Plot Plan

Another item of interest on the site plan is the building finished floor elevations for the garage and floor plan. The length of the properties boundaries are also shown.

Electrical Drawings

You should be able to find all the HVAC equipment that requires electrical power on the electrical drawings. Shown below are two VAV’s (VAV 1-5 & VAV 1-6) that are provided with electrical power. You can read the description as circled in red as the electrical panel number and the circuit in that panel, such as; P5-16 (Panel 5, Circuit 16).This indicates that VAV 1-5 has electrical conduit and wire coming from panel 5 and circuit #16 in that panel.

Electrical Drawings
Electrical Drawings

Structural Drawings

The structural engineer will design the support framing for the building in addition to miscellaneous equipment supports and concrete pads. They will do all of the calculations to ensure that the structure can support the various weights, wind loads, seismic activity and other stresses bearing on the building and its components. For the HVAC contractor this could include the design of special roof duct supports and equipment pads.

Below is a concrete pad designed by the structural engineer and shown as a detail on the structural drawings.

Equipment Pad
Equipment Pad

Column Lines

“Column lines help you find common areas on different floors.”

If you locate the intersection of column line “4” & “N” on the first floor, then you can find the same location directly above on the 2nd floor by finding the same column lines. This is helpful when trying to trace sheet metal, piping or utility risers that penetrate the floor.


Architectural, structural and all mechanical drawings should have the same column line references.

Column Lines General Drawing Layout
Column Lines General Drawing Layout

Dimension lines

Dimension lines are used to indicate the distance between two points.

Dimension Lines
Dimension Lines

Dimension lines can be shown many different ways, such as shown here with arrows as end points or hash marks.

Dimension Lines Arch Drawings
Dimension Lines Arch Drawings

Hidden Lines

Hidden lines represent lines traveling under or on the inside of an object. These invisible portions of an item are often represented by dashed lines. Hidden Lines give an indication of items that are behind or below another item, as shown here highlighted in yellow. If you see dashed lines, those are part of a hidden item. The hidden items in this drawing show other sheet metal air ducts traveling under the duct above.

Hidden Lines - General Drawing layout
Hidden Lines – General Drawing layout

Elevation View

This is the view that shows the outside or inside of the building from a standing position, eyes forward.

Elevation views are used to determine sheet metal riser lengths.

Elevation View
Elevation View

Watch this Video for a quick overview of a complete set of Construction Drawings.

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Now click the link below for Chapter #2 “Architectural Drawings” to get an overview of these drawings.

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