HVAC Drafting Techniques2015

Part 2 Introduction to HVAC Drafting Techniques

Page 1 of 21

Part 2 Introduction to HVAC Drafting Techniques Introduction Engineers, designers, and draftspersons are constantly working on new plans for heating, ventilating, and air-conditioning systems in new buildings as well as plans for the renovation of existing buildings. Much of the design of such systems is accomplished by the use of mathematics, good judgment, and drafting. Mathematical formulas are used in calculating the heat loss and heat gain of various structures, the required volume of air, the sizes of ducts needed to carry this air, and similar details. Good judgment is gained from experience and is used to determine the type of fuel used for a particular building and to select the best HV AC (Heating, Ventilating, and Air Conditioning) system and equipment. Drafting is the means of using lines, symbols, dimensions, and notations to convey the engineer's calculations and design to the workmen on the job.

Fig 2-1 Schematic of air handling system

Types of HVAC HVAC Drawings Drawin gs It should now be clear that the architect plans and designs buildings; the engineer or HVAC designer usually lays out the complete HVAC systems for the architect's buildings; and the HVAC draftsperson transforms the engineer's designs into working drawings. In preparing the HVAC drawings, an outline of the architect's floor plan (s) is usually used to overlay the various HVAC systems. It should be noted that the architect’s drawings are usually too detailed to be used directly. They need to be simplified to allow the emphasis of the mechanical systems. HVAC drafters are called upon to prepare complete construction drawings. These engineering drawings are used to provide an overall picture of a job for sales, marketing, estimating, or engineering purposes.


Page 2 of 21

Engineering drawings for HVAC jobs are usually prepared by mechanical drafters employed by consulting engineers, contractors, or sales engineers. Information found on engineering drawings includes the following: Locations of major air handling components such as air conditioners, ducts, • exhaust fans, and other equipment. Basic dimensions • Typical sections • Notes to clarify complicated situations •

Fig 2-2 Partial HVAC floor plan

Fig 2-3 Partial section view


Page 3 of 21

Fig 2-4 Isometric piping drawing

Graphic Symbols Ductwork is used to transmit air from the air handling equipment to the space to be conditioned. Fig. 2-1 shows a simplified diagram of how such a system operates. The purpose of an HVAC drawing is to show the location of air-handling and other HVAC equipment; to show the sizes and routes of the various ductwork (both supply and return air); to show the air outlets, including the volume and velocity of air from each; and other necessary information required in a duct system. In the preparation of such drawings, symbols (Fig2-5) are used to simplify the drafter's work and to save time.

Fig 2-5 Mechanical drawing symbols


Page 4 of 21

In drawing HVAC plans, most engineers and designers use the symbols adopted by the ANSI (American National Standards) or CSA (Canadian Standards Association). However, consulting engineering firms, as well as contracting-design firms frequently modify these standard symbols to fit their own needs. When these standard symbols are modified, it becomes necessary to provide a symbol list, or legend, on the drawings for the workmen's interpretation. Fig. 2-5 shows a list of HVAC symbols that have been used by a consulting engineering firm. Fig 2-6 shows a partial legend used on a drawing.

Fig 2-6 Partial legend of symbols

Applications The sketches on the following pages show the symbols found in Fig. 2-5, along with a pictorial illustration of each, so that the student drafter will be able to visualize the meaning of each symbol more clearly. In addition, a practical application of each symbol is given. The student drafter should study these pages very carefully.


Page 5 of 21


Page 6 of 21


Page 7 of 21


Page 8 of 21


Page 9 of 21

HVAC Drafting Standards Before developing specific knowledge and skills in the areas of HVAC design, the student must learn several general items that apply to all areas of structural drafting. These items are grouped under the general heading structural drafting techniques and include the following: HVAC drafting line work • HVAC drafting lettering • HVAC drafting scale use • HVAC drafting paper sizes • HVAC drafting title blocks and borders •

Linework As is the case in all types of drafting, HVAC drafting has a set of line types that are commonly used. This set includes object lines, hidden lines, phantom lines, centerlines, dimension lines, extension lines, cutting plane lines, and break lines. Figure 2-7 illustrates each of these types of lines drawn to an acceptable width. It is evident from Figure 2-7 and 2-2 that object lines may be drawn to one of several widths. Actually, in HVAC drafting, this is true of all lines. The examples provided in Figure 2-7 are meant to serve as guidelines for reference when preparing structural drawings. However, it should be noted that though the shapes of the lines should agree with the examples provided, the widths may actually vary slightly in use. In application, line widths are sometimes varied. This is done to emphasize one aspect of a drawing or deemphasize another aspect. The width of a line is determined by how the line is to be used and the individual circumstances of the drawing. With CAD, linework is taken care of by the software and plotter.

Fig. 2-7 Commonly used line types in structural drafting


Page 10 of 21

Line Types The most commonly used line is the object line. An object line is a continuous solid line used to show the outline of the object being drawn. Object lines are drawn in slightly varied widths depending upon the amount of emphasis desired by the drafter, Figure 2-8. Hidden lines are used almost as frequently as object lines. They show the edges or outlines of HVAC components that are important but could not be seen by an actual viewer of a given part of the HVAC system. Hidden lines are composed of a number of very short line segments, Figure 2-9 and Figure 2-10. Phantom lines are used to show wiring connections between thermostats and heater relay, Figure 2-9. Centerlines are used frequently in structural drafting to locate centers of round ductwork on plans and may be substituted for “flexible duct”. Centerlines are thin lines broken by a short dash. Centerlines are often extended beyond the object being drawn and used as extension lines to enclose dimension lines. Figure 2-9 illustrates how centerlines are used on HVAC plans. Dimension lines are not typically shown on HVAC drawings. However, the sizes of components are usually given, Figure 2-10. Cutting plane lines are thick lines that are used to, in a sense, cut through an object for the purpose of clarification. A cutting plane line indicates the area that has been sliced through and a direction for the viewer’s sight. A sectional view is then drawn showing the viewer what would actually be seen if the object were sliced as indicated. Figure 2-10 shows two examples of how cutting plane lines are commonly used in HVAC drafting. Refer to Figure 2-11 for the referenced section view. Break lines may be constructed mechanically or freehand. In either case, they are used to cut out unnecessary or lengthy portions of a drawing. This allows the drafter to show only those portions of a detail that are needed to convey an idea, thereby economizing on space and drafting time. Figure 2-8 shows an example of a freehand break line.

Line Use Example (Student projects) Line Width (mm) Extra Thin 0.18 Thin 0.25

Medium 0.35 Thick 0.50 Extra Thick 0.70

Recommended Use of Line Hatching, Architectural features. 2.5mm Text, Dimensioning, Leaders, Extension Lines, Break Lines, Hidden Lines, Dotted Lines, Dashed Lines, Setback Lines, Centre Lines, Interior Features (i.e. symbol interior). 4mm to l0mm Text, Object Lines (ie. outline of ductwork for emphasis) 6mm to l0mm Text, Section Cutting Plane Line. 13mm to 25mm Text, Match Line, Border.


Fig. 2-8 Object line samples

Fig. 2-9 Hidden, phantom, freehand break, and centerline samples

Page 11 of 21


Fig. 2-10 Dimension and cutting plane line

Fig 2-11 Referenced Section View

Page 12 of 21


Page 13 of 21

Lettering Clear, legible drafting lettering is one of the structural drafter's most important skills. Every structural drawing requires a greater deal of lettering. A well developed, legible style of lettering adds a professional quality to drawings. In addition, it makes drawings easier to work with and read. The best HVAC drafting lettering is simple, easy to read, and can be done rapidly. The HVAC drafting student should use uppercase vertical lettering. When the student is called upon to work on a drawing prepared by another drafter, he or she will then be able to match the lettering style. This is a very common occurrence on the job.

Text Use Example (Student projects) Text Style General Label

Recommended Use For all text, except as a title heading, or title block information. For title heading and title block information

Properties of Text Styles General: RomanS font, 0.8 width factor, 2.5mm height when plotted

Label:

RomandD font, 0.8 width factor, 5mm height when plotted

Note: Every drawing view (i.e. plan, detail, elevation, section, etc.) shall contain the view name and scale as in:

Main Floor Plan - HVAC (the title info is Label @ 5mm) Scale 1:100

(the scale info is General @ 2.5mm)

Drawing Scale and Units of Measure (Metric) The International System of Units (S.I.) must be used to prepare all drawings. The unit for linear dimensioning is the millimeter, except where the scope of the drawing requires the use of the meter, such as in site plans. Whole numbers will indicate millimeters, e.g., 435, 4300, etc.; and decimalized expressions to three places of decimals will indicate meters, e.g., 5.435,4.300, etc. All other dimensions and notations should be followed by the unit symbol.

Preferred Scales The selection of scale for drawings must be given careful attention to ensure that all information required to carry out work is accurately conveyed in the most economical space. The preferred scales for various drawing components are provided in the following table:


Page 14 of 21

Scale Selection The scale selected for a particular drawing should be determined by consideration of: The type of information to be communicated; • The need for the drawing to communicate adequately and accurately the • information necessary for the particular work to be carried out; The need for economy in time and effort in drawing production. •

Indication of Scales The drawing scale should be stated in the title panel of each drawing sheet. e.g., Scale: 1: 100 (if only one view is shown) or

Scale: NTS

or

Scale: As Noted

(if the view is not to scale) (if there are more than one view)

Where two or more scales are used on the same sheet, the particular scales should be clearly indicated under each view.


Page 15 of 21

Standard Metric Sheet Sizes The "A" series of paper sizes is a rationally designed system based on a sheet having an 2 area of 1 m (841 x 1189 mm) from which all other sizes are derived by successively dividing it into two equal parts parallel to the shorter side. Consequently, the ratio of areas of any two successive sheets is 2: 1 and the ratio between the short side x and the long side y, of any sheet, is 1 √2. i.e., the ratio between a side and the diagonal of a square.

Trimmed sheet sizes are designated in the following table by a number indicating the number of divisions that have been made. For example, sheet size A4 is produced form basic AO sheet by four successive divisions. Sizes larger than AO may be designated by a prefix. Size 2AO is a sheet 1189 x 1682 mm and size 4AO is a sheet 1682 x 2378 mm. Designation AO Al A2 A3 A4

Dimensions, mm

Border Sizes

41 x 1189 594 x 841 420 x 594 297 x 420 210 x 297

786 x 564 539 x 390 365 x 267

| |- common sheet sizes |


Page 16 of 21

Border on an A1 sheet

Fold lines on an A1 sheet

Folding an A1 sheet


Page 17 of 21

Submission of Projects Unless otherwise noted, all projects shall be submitted on-time and it the following format: Hardcopy: Electronic copy

Plot, Monochrome, trimmed, folded, transmittal Email PDF and DWG file that includes plot layout

File Formats All electronic files must have the proper naming convention to be submitted for evaluation. Every file or email must contain the course, project number, and student’s name.

AutoCAD files: E2P6M3SJE.dwg Course Project Discipline/Sheet Number File created by

nd

E2 = Structural CAD (2 course) P6 = Project number 6 M3 = Mechanical discipline, sheet 3 SJE = Stephen James Ethier

Email: Subject Line: E2P6 Subject line must contain the Course and Project Number Content: simplified transmittal form listing student name (or names), list of document number and document title, and purpose of submission.

PDF:

E2P6M3SJE.pdf

Word:

E2P6DOC6SJE.doc (do not send docX )

Penalties for Late Submission To be fair to the students that do complete their work on time, the following penalties will be applied to those that do not submit their work on time. 5% (of 100) late the same day 10% (of 100 late the next day) 20% (of 1 00) late the second day 30% (of 100) late the third day After 3 days the project will be assigned a value of 0, but it must be submitted.

Sample Drawings The following pages contain samples of actual commercial projects.


Page 18 of 21


Page 19 of 21


Page 20 of 21


Page 21 of 21

HVAC Drafting Techniques2015

Recommend Documents