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Sheet Metal Shop Drawings

MEP Academy Instructor

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September 27, 2020

Chapter #7 – Sheet Metal Shop Drawings

Shop drawings should be created by someone in the company familiar with detailing. Detailing is the process of taking the engineered set of drawings and converting them into shop drawings that the field will use to install the sheet metal.

Sheet Metal Detailer

The sheet metal detailer’s job is to coordinate the layout of the ductwork with all other trades in order to avoid collisions or conflicts. This position is held by a union member for companies that are signatory to a local Sheet Metal Union. Their job is to ensure that the sheet metal fits within the space and to show all the required dimensions on the drawing so as to make the field installation go smoothly and without wasting ductwork and fittings because they don’t fit into the space shown on the drawings.

The shop drawings will show the ductwork exactly where it needs to be installed in order to avoid building components and other trades.

The sheet metal detailer will review the architectural, structural, electrical, plumbing and other trade drawings in an effort to avoid installing ductwork where these trades have their systems and where structural supports and architectural items are to be installed.

Detailed Shop Drawings

Looking at the sheet metal shop drawing below you can see that additional items are shown on these drawings compared to the engineered set. These drawings are drawn in CAD (Computerized Aided Drawings), which is drawn on a special computer program. If you have a small project then using CAD may not be feasible, and in this cases the detailer will just fill out the sheet metal fabrication shops order forms directly from the engineered set of drawings and from what is discovered during a site visit for existing buildings.

The numbers in the red circles correspond to the following;

#1 (Duct Size & Joint Length) This shows that the rectangular duct that is 70” x 18” in size is 56 1/4” in length. This duct is made from a 5 foot (60 inch) coil width, and the difference is from the joint. 60” coil width – 3 3/4” joint (1-5/8” each joint) = 56 1/4” in length.

#2 (Plenum Size & Length) This is the plenum off of the VAV box, which is a duct that is 20” x 17-1/2” in size by 36” in length.

#3 (Duct Elevation) This shows the bottom and top elevation of the ductwork. This shows that the bottom of the duct is 9’-11” off of the floor, and that the top of the duct is at 11’-5” off of the floor.

#4 (Service Access) – According to the manufacture or local code authority, each piece of equipment, valve or accessory that needs adjustment or service is required to have an unobstructed access area. As shown in item #4 the hatched area next to the VAV boxes must be kept clear so that a service technician can access the controller.

#5 (Ceiling Height ) – The height of the ceiling is indicated to be 8’-2”

#6 (Benchmark Distance) – The location of the edge of the ductwork is indicated as being 10’-0” from the column line.

#7 (Wall Opening) – Top and Bottom elevation of Return Air Boot opening in Fire-Rated Wall, as can be seen by the Fire/Smoke Damper.

#8 (Direction) – BF = Bottom Flat. This is a transition fitting that is changing the size of its depth. In order to inform the fabrication shop and the field installer which side remains flat these acronyms are used. It’s also possible to install a concentric transition, where both sides converge evenly.

#9 (Duct Offset) – This indicates that the duct needs to drop by 16” in order to get under the large main supply air duct. It’s important to remember this when you are working with a set of engineered plans that haven’t been detailed into shop drawings. Remember to add extra fittings when crossing ducts.

#10 (External Insulation Wrap) – The dotted line on the outside of the duct indicates that this ductwork will get wrapped with insulation, most likely by your insulation subcontractor.

#11 (Internal Liner) – These dotted lines on the inside of the duct indicate that the ductwork is lined with acoustical liner.

From Shop Drawing to Fabrication Equipment

From the shop drawings the detailer will either draw the required duct and fittings onto an order form or the CAD software will download the information to the shop fabrication equipment with or without the shop superintendent’s modifications.

For those that have an integrated software system where the CAD drawings can be directly sent to the fabrication equipment, this will save a lot of time by not having to draw out each piece required to be fabricated or enter data into the coil line or plasma cutter.

Detailing for Retrofit Projects

Detailing for existing buildings can be done in a similar manner as that of new construction, except that you will need to do a site survey to document what is in the space where new sheet metal or HVAC equipment will need to be installed. Again, based on the size of the project and the requirements of the RFP (Request for Proposal) the use of CAD may or may not be used.

For small retrofit projects the detailer will visit the project site and make the measurements required to get the needed ductwork and fittings fabricated. There is no need to go through the expense of drawing everything in CAD.

Control / Reference Point

The construction project will have one or more control points from which everything can be measured from in order to ensure the accurate location of walls and other trades. The control point is determined by a field engineer and has an X, Y, Z reference point.

Navisworks by Autodesk (Collision Detection)

Most large new construction projects are built within some form of modeling software like Autodesk Revit, Bentley or many others.

In the enclosed video at about the three minute mark you will see that the Navisworks software will pick up a collision between a sheet metal duct and a structural beam. Navisworks combines the different designs from the various trades (Architectural, Structural, HVAC, Electrical & Plumbing) and combines them together, and then searches for clashes that occur between them. Clashes occur when two different designers are trying to occupy the same space in the building, like the duct that is placed where a structural beam is located.

Using Autodesk Navisworks helps eliminate change orders and costly field errors by finding them before they get installed.

AutoDesk Navisworks

Shop drawings are done in AutoCAD, Autodesk Revit MEP or some other modeling software that allows for the coordination with other trades using Navisworks to ensure that the sheet metal will fit within the building without hitting anything.

Revit

BIM (Building Information Modeling)

The use of BIM is widely used throughout the industry for commercial contractors doing new construction projects. Often the requirement to use BIM is specified in the design criteria for many Federal, State and local Municipalities in addition to the private sector. BIM make coordination easier and reduces the amount of change orders due to the collision checking before construction begins.

BIM – Building Information Modeling

The sheet metal estimator will need to provide hours in the estimate to cover the detailing requirements per the RFP (Request for Proposal) or ITB (Invitation to Bid). If there are no requirements then your companies minimum level of detailing required to accomplish the ordering of ductwork and fittings.

Companies that maintain historical data from completed project will be able to look at metrics from those projects which could help determine the hours required for the current project. A metric like, percentage of detailing hours to total field hours would be helpful.

10% Detailing (historical data feedback)

Example: Current Project has 2,000 field labor hours.

Calculate detailing: 2,000 Field Hrs x 10% = 200 detailing hours

Below is a screen shot of a small section of the Sheet Metal Material & Labor Summary tab of the MEP Academy Estimating spreadsheet that allows you to enter a percentage of your total field labor for detailing.

Detailing on Estimating Spreadsheet — Detailing Option on MEP Academy Estimating Spreadsheet

Summary

The detailer will create shop drawings by reviewing the location of all the architectural, structural, electrical and plumbing elements in addition to the various other trades that require space within the building for their component.

The detailer will coordinate with the other trades to ensure that everything fits within the space allotted. It’s possible that software like Navisworks will be used to detect collisions automatically within the software program, thereby minimizes field change orders.

Detailing can be done on a computer using some form of CAD, or on smaller project detailing can be done by hand and drawn out on an order form.

Detailed drawings (shop drawings) shows the size, length and duct joint information for each piece of ductwork and fittings, along with their elevation height.

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Chapter #1 – General Layout of Drawings
Chapter #2 – Architectural Drawings
Chapter #3 – Plan, Elevation, Section Views and Details
Chapter #4 – HVAC Mechanical Drawings
Chapter #5 – Understanding HVAC Symbols
Chapter #6 – Drawing Scales (How to Read Scales including Metric Scales)
Chapter #7 – Sheet Metal Shop Drawings

How to Read Drawing Scales

MEP Academy Instructor

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September 27, 2020

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Chapter #6 – Drawing Scales (How to Read Scales including Metric Scales)

It’s important that you understand how to read the various scales of architectural and engineered drawings. You will learn the following in this section.

How to read an Architectural scale (mostly used for buildings in the U.S.). Architect scales, such as 1/4˝ = 1´-0˝ (1/48 size) or 1/8˝ = 1´-0˝ (1/96 size)
How to read an Engineers scale (mostly used for roads and topographical measurements) Engineer scales, such as 1˝ = 10´ or 1˝ = 50´
How to read a Metric scale (mostly used for buildings in other parts of the world)
How to determine the scale of a drawing where the scale isn’t indicated

It’s not practical to draw a building to full scale, so various ratios are used to represent the actual size of the building. The scale provides a quick method for measuring drawn objects, such as the length of ducts, pipes, and electrical conduits.

The scale is usually shown in the lower right hand corner of the drawing or under the title of the page. There are often many different scales used in the same set of drawings, as they can be on floor plans, elevation pans, section views and details.

Often times you will find all three bits of information located together as in the above drawing and as shown in the insert below. The Title of the Drawing, the scale and the North arrow indicator.

Bar Scale

The bar scale here is accurate even when reduced, so if your drawings have one of these all you have to do is put your ruler up to the scale bar and see which of the scales match exactly the numbers on the bar as shown below. If none match, then your drawings aren’t to scale and weren’t printed correctly.

Set your ruler so that the zero (0) on your scale aligns with the zero (0) on the bar scale, then check to see if the rest of the numbers line up exactly.

Bar Scale Chart 1/4" = 1'-0" — Bar Scale Chart 1/4″ = 1′-0″

As seen above the zero’s (0) and the four’s (4) line up exactly between the ruler and the drawings bar scale, so you know you got the right scale. If they didn’t match, then you would try another scale on your ruler until you found one that did.

If there isn’t a bar scale, then there are other methods to confirm the drawings scale. It’s important to confirm you have the correct scale, otherwise all of your material lengths will be incorrect.

Determining the Scale when No Scale is Shown

Sometimes the scale is not shown on the drawings are is indicated incorrectly. By using some know distance like a doorway or the distance between columns, you can determine the true scale.

Everything on the drawing has been drawn to some scale so it’s a matter of finding something that you know the dimension of and laying your scale down next to it to find the right scale. For instance, most doors in our local area and in the U.S. are about 3 feet wide, so if you measure a doorway it will let you know the proper scale to use.

Checking the scale using the doorway and the 1/4″ = 1′-0″ scale.

Checking the scale using a doorway (This indicates that 1/4″ is incorrect)

Looking at the above we can see that the doorway measures 1-1/2 feet on a 1/4′ scale. Unless this is a home for the 7-Dwarfs in the tale of Sleeping Beauty than the scale isn’t a 1/4″. Next we’ll try the 1/8″ = 1′-0″ scale as shown below.

Using a 1/8″ = 1′-0″ scale gives a measurement of a 3 foot doorway, which is the correct dimension. This verifies that the correct scale to use is the 1/8″ scale.

You can also use a dimension that is already given on the drawings such as the width of a duct that has been drawn using double lines as shown below;

Using a section of duct to determine the scale

Using the dimension of the ductwork it is determined that the scale is 1/8″ = 1′-0″ as shown in the image above. The 50″ x 30″ duct measure 4′-2″ on our scale which is equivalent to 50 inches.

How to Use the Metric Scale (SI Units)

The Metric system is widely used around the world and on some Government projects, so it’s imperative that you understand both methods. The following scale is derived by measuring the drawings and multiplying every centimeter (cm) on the drawing by the denominator of the scale ratio such as 1:50 which means that for every 1 cm measured on the drawing it is equivalent to 50 cm in real life.

Basically the scale is represented by two numbers in a ratio, with the first number being how many centimeters are shown on your drawing followed by the second number which is separated by a colon (“:”), then the matching length of the real item to be built.

If we blow up the image of the scale, we see that there are two scales referenced at one end as opposed to the imperial version that showed 1/4” on the left side and 1/8” on the right side of the scale.

Metric Scale 1:50

The two scales shown are 1:50 and 1:500. What they represent is the following;

1:50 means that when you measure 1 cm on the drawing it is equivalent to 50 cm of the real item to be built. 1:50 is also equivalent to 1/2 of meter for every cm on the drawings, because 100 cm is equal to a 1 meter.

Metric Scale 1:50. 1 cm = 1/2 meter — Metric Scale 1:50. Measuring 1 cm on the drawing = 1/2 meter

Metric Scale 1:500

Using the yellow highlighted 1:500 scale means that when you measure 1 cm on the drawing it is equivalent to 500 cm of the real item to be built. 1:500 is also equivalent to 5 meters for every 1 cm on the drawings, because 100 cm is equal to 1 meter; 500 cm is equal to 5 meters.

Metric Scale 500cm (1 cm on the drawing equals 5 meters) — Metric Scale 500cm (1 cm on the drawing = 5 meters)

Metric Scale Measuring 2 cm on the drawings equals 10 Meters — Metric Scale 1:500 (2 cm on Drawings = 10 Meters)

To verify that you have the correct metric scale you can use a Bar Scale or find a known dimension on the drawings and put your scale next to it until you get the correct scale.

doorway metric measurement — Using a Doorway to Determine Metric Scale

Making a measurement with a known length

Metric Scale Chart 1:50, 1:100 and 1:500) — Metric Scale Chart (1:50, 1:100 and 1:500)

Architectural Scale

The most common scale in the USA is 1/8″ = 1′-0″ & 1/4′ = 1′-0″.

We will also show you how to verify that the scale indicated on the drawings is correct. Often times the engineer incorrectly marks the scale or no scale is indicated, so having a way to verify the scale is important to an accurate takeoff. The scale is indicated in various locations on the drawing. Each engineer has their own preferred location. The scale is often found under the floor plan or section name description as such;

Reading a manual scale is easy if you understand the basics of each scale size. As shown in the image below there are two scales on the same side of the same scale. The 1/8″ and 1/2″ scales are show on the same side.

Reading a Scale — How to read a scale. A lot of scales offer options for scale lengths.

Software Programs

If you own modern estimating software then the scale is set in the computer according to the scale indicated on the drawings. Occasionally the scale indicated on the drawings is incorrectly marked, so knowing how to confirm the scale is important.

There are also other programs like Blue Beam or Adobe that have various scale reading features of their software packages.

Next is Chapter #7 “Sheet Metal Shop Drawings” to see how drawings are prepared for use in the field.

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Chapter #1 – General Layout of Drawings
Chapter #2 – Architectural Drawings
Chapter #3 – Plan, Elevation, Section Views and Details
Chapter #4 – HVAC Mechanical Drawings
Chapter #5 – Understanding HVAC Symbols
Chapter #6 – Drawing Scales (How to Read Scales including Metric Scales)
Chapter #7 – Sheet Metal Shop Drawings

Understanding HVAC Symbols

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September 27, 2020

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Chapter #5 – Understanding HVAC Symbols

In order to understand how to read HVAC drawings, you have to understand the road signs (HVAC Symbols). These vary from one engineer to the next, but there are some similarities that will help you figure the differences out. HVAC Symbols work like the road signs you are familiar with; they allow you to discern their meaning by a visual icon or image with very little use of words.

Without HVAC symbols the drawings would be crowded with words and sentences in an attempt to explain what is easily explained with a symbol.

There are symbols for all kinds of equipment, duct specialties, piping components and for all other trades. Symbols are the unspoken language in the construction trade. They convey meaning without words or in conjunction with abbreviations.

There should be a Legend of symbols on the mechanical drawings.

You will find that there is no industry standard and that symbols can vary from one engineer to the next. Often if they are using the same CAD program and the symbols that are standard with the program then you will see similarities.

Don’t be confused by the variations of the same symbol from drawing to drawing. Focus on what the symbol is trying to convey.

Supply, Return & Exhaust Symbols

The following are used often throughout the mechanical drawings to indicate which type of air is in the ductwork, or which type of air distribution is being referenced.

The three most common being supply, return and exhaust. An “X” in a square or round shape is indicative of Supply Air, while a single Diagonal line indicates return air.

The following symbols indicate the type of air but also that of a riser duct. A riser duct is one that penetrates a floor. When the line is solid, it indicates that the duct is going up, and if the line is dashed, it indicates that the duct is going down.

Duct Risers in Shafts

In multi-story buildings it’s probable that you will have a shaft, which is usually a drywall enclosure that is fire rated to allow utilities, including HVAC ductwork to travel from one floor to another. When the ductwork leaves or enters the shaft it requires a fire damper or a combination fire/smoke damper, in order to prevent fires or smoke from traveling from one floor to another.

When looking at the shaft, you can determine which direction the ductwork is going by whether the lines are solid or dotted. Solid lines indicate that the ductwork is going up, and dashed lines (Hidden Lines) indicate the ductwork is going down.

Again, to distinguish which direction the above ducts are going, you only need to remember the rules governing hidden lines. The shafts on the left side show hidden lines (dashed lines) in the riser indicating that the shaft is headed downward, while the shafts on the right show solid lines indicating that these are duct risers going upward.

The above shows what a rectangular duct looks like in each case, while the below represents a round portion of duct that rises up and down. The round duct riser goes down on the left side as indicated by its dashed lines, and the other side goes up as indicated by the solid lines.

Air Distribution

Air distribution devices are used at the end of branch ducts or tapped onto the side of ducts to allow air out of or into the ductwork. Air distribution grilles, registers, diffusers and linears are chosen to allow for the proper dispersion of the air into the room based on acceptable noise criteria, throw distance and throw pattern. The arrows show the direction of the airflow. Supply shows the arrow exiting the air diffuser, while return and exhaust show the arrow pointing into the grille.

Supply Return Exhaust Grilles

he arrows show the direction of the airflow. Supply shows the arrow exiting the air diffuser, while return and exhaust show the arrow pointing into the grille.

Below is an example of what it might look like on the drawings. Note that different engineers will use different symbols. The below image shows the symbols indicating supply, return and exhaust air distribution devices.

Air distribution grilles, registers and diffusers will often have an acronym that matches an air distribution schedule on the drawing where the equipment is listed, which will define the make and model number for each piece & indicate the CFM.

Ductwork Symbols

Most ductwork is either shown in single line or double line. There are also various types of ductwork that have their own symbols, such as flexible duct which is often shown as a squiggly line.

Ductwork can be internally lined for acoustical or thermal reason, that is for the reduction of sound transmission or for the reduction of heat loss or heat gain. This is usually indicated by a dashed line within a solid pair of lines.

In retrofit projects where the existing ductwork needs to be removed, the symbol that indicates this is usually some form of diagonal hash marks as shown below. Labor must be included in your estimate to remove this ductwork.

When existing duct is removed as shown above, but not all of the existing ductwork gets removed, there is a symbol that indicates a point at which the existing duct on one side of the line remains, while the duct on the other side of the line gets removed (Demoed)

When new ductwork is attached to existing ductwork, engineers will indicate this by using a point of connection symbol. The difference between the new ductwork and the old can also be determined by the type of line used. Lines that are dotted, dashed or thinly drawn are indicative of existing ductwork, while solid lines indicate new.

Routing ducts through buildings often require that they rise or drop to get around obstacles. This is indicated with an arrow and with a letter; R (Rise), D (Drop). As a sheet metal estimator you should add a couple of angles (45-degree elbows) or an offset fitting.

A special type of duct is used to prevent vibration and noise from transmitting down the ductwork from the source. The flexible duct section is used for equipment, but there are also special flex section used for seismic breaks.

Dampers

Fire Dampers

Fire dampers are shown as a dotted or solid line through the duct at the point where it penetrates the fire rated wall, accompanied by a solid diamond, square or other shape, often with the abbreviation FD (Fire Damper) as shown below.

Smoke/Fire Damper

This is a combination of two types of protective dampers, a fire damper, which protects against fires, and a smoke damper, which closes off the air by motorizing a damper closed.

Volume Dampers

The air in an HVAC system requires balancing in order that the air gets to the room in the quantity that the engineer intended. Volume dampers are shown as various straight lines perpendicular to the duct with a small handle.

Automatic Control Dampers

In order to control dampers automatically they need to have some form of actuator that will modulate, open or close to perform some function of the HVAC system.

Auto Control Damper — Automatic Control Damper

Miscellaneous Equipment

There will be miscellaneous pieces of HVAC equipment that will be inserted into the ductwork. Make sure to review what each symbol represents, as piece of equipment installed in the ductwork often requires transitions or special connections. As shown below this in-line coil which is larger than the ductwork will require two transitions.

Duct Mounted Coil

This next symbol represents a piece of equipment, in this case a heating coil as shown by the red outlined box in the image below, but it could be any type of coil.

One of the ways to tell this is a coil is that there are pipes attached to it. Usually you will see two pipes entering the coil, but the engineer has chosen to show only one of the two pipes.

Symbols for a Typical VAV Terminal & Ductwork

The image below is of a typical VAV (Variable Air Volume) terminal, this is a box connected to the ductwork that varies the volume of air based on the thermostats setting.

This symbol represents a piece of equipment, in this case a Variable Air Volume terminal box with a lined plenum. The VAV provides a variable amount of air to the diffusers based on the thermostat setting and current room conditions. This could also represent a CAV (Constant Air Volume) terminal box.

Point of Connection (POC). This indicates where the new ductwork connects to the existing ductwork. Everything from this point forward is new, and everything before it is existing. Often, the new ductwork is shown in dark lines, while the existing is drawn lightly. Also, sometimes the (N) new ductwork includes an (N) before its size, to indicate its new.

As we learned above the “X” within a box refers to Supply Air, so this here is referencing a Supply Air Diffusers. This also shows that the SA (Supply Air) diffuser blows air in four (4) directions, as indicated by the arrows.

Volume Dampers are used to balance the system so that the correct amount of air (CFM) is provided through the diffuser to the space.

VAV (Variable Air Volume) Terminal. This is a piece of equipment purchased from a supplier, and manufactured by Titus, Metal Aire, Krueger, or similar. This VAV terminal will adjust the volume of air delivered to the space based on the demand of the thermostat.

Return Air Grille with a sound boot. This grille provides for air to return from the space back into the attic where it will make its way back to the system by the negative pressure created by the HVAC system. On the Return Air Grilles there is a sound boot, or a piece of lined sheet metal with an elbow to prevent noise from being carried to other spaces.

Return Air Grille Symbol — Return Air Grille

Thermostat

The thermostat controls the temperature setting for the room and controls the HVAC equipment. The symbol for a thermostat is often just a circle with a “T” inside as shown below. The thermostat shown below is controlling a VAV box.

Indication of Demolition

Items that are hashed out as shown in this picture indicate items of a retrofit project that need to be removed. This show two fans and duct that needs to be demoed and removed.

Equipment Tags

These are special symbols that identify the equipment by an acronym and a number. This helps tie together the equipment schedule that list all the equipment with tags that can be located somewhere on the floor plans to show where that piece of equipment resides in or on the outside of the building. This equipment tag (AC-1) represent Air Conditioner #1.

Drawing Notes

Drawings will use numbered tags that refer to a column of numbered notes that might be off to one side of the drawings. Putting the description or notes directly on the drawing next to the item could make the drawing messy and hard to read, it’s easier to put a small number next to the item that the note references.

Detail and Section View Symbols

As mentioned previously, these are drawing road signs that point you in the direction of another drawing where a detail or section view is available. These special symbols identify what other drawing that you need to review to understand in more detail the area referenced.

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Next is Chapter #6 “Drawing Scales” to see how scales effect your takeoff and how to read scales including metric scales.

Chapter #1 – General Layout of Drawings
Chapter #2 – Architectural Drawings
Chapter #3 – Plan, Elevation, Section Views and Details
Chapter #4 – HVAC Mechanical Drawings
Chapter #5 – Understanding HVAC Symbols
Chapter #6 – Drawing Scales (How to Read Scales including Metric Scales)
Chapter #7 – Sheet Metal Shop Drawings

HVAC Mechanical Drawings

MEP Academy Instructor

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September 27, 2020

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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 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 Detail Drawings

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

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.

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.

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.

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.

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.

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).

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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.

Chapter #1 – General Layout of Drawings
Chapter #2 – Architectural Drawings
Chapter #3 – Plan, Elevation, Section Views and Details
Chapter #4 – HVAC Mechanical Drawings
Chapter #5 – Understanding HVAC Symbols
Chapter #6 – Drawing Scales (How to Read Scales including Metric Scales)
Chapter #7 – Sheet Metal Shop Drawings

Chapter #7 – Sheet Metal Shop Drawings

Sheet Metal Detailer

Detailed Shop Drawings

From Shop Drawing to Fabrication Equipment

Detailing for Retrofit Projects

Control / Reference Point

Navisworks by Autodesk (Collision Detection)

BIM (Building Information Modeling)

Summary

Chapter #6 – Drawing Scales (How to Read Scales including Metric Scales)

Bar Scale

Determining the Scale when No Scale is Shown

How to Use the Metric Scale (SI Units)

Metric Scale 1:50

Metric Scale 1:500

Architectural Scale

Software Programs

Chapter #5 – Understanding HVAC Symbols

Supply, Return & Exhaust Symbols

Duct Risers in Shafts

Air Distribution

Supply Return Exhaust Grilles

Ductwork Symbols

Fire Dampers

Smoke/Fire Damper

Volume Dampers

Automatic Control Dampers

Miscellaneous Equipment

Duct Mounted Coil

Symbols for a Typical VAV Terminal & Ductwork

Thermostat

Indication of Demolition

Equipment Tags

Drawing Notes

Detail and Section View Symbols

Chapter #4 – HVAC Mechanical Drawings

HVAC Mechanical Equipment Schedule

Zoning Map

HVAC Floor Plan

HVAC Detail Drawings

HVAC Controls Drawing

Plumbing Drawings

Structural Drawings

Demolition Drawings

Drawing Revisions

Specifications on Drawings

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