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Mechanical systems drawing is a type of technical drawing that shows information about heating, ventilating, and air conditioning ; it is a powerful tool that helps analyze a complex system. These drawings are often a set of detailed drawings used for construction projects; it is a requirement for all HVAC work. They are based on the floor and reflected ceiling plans of the architect. After the mechanical drawings are complete, they become part of the construction drawings, which is then used to apply for a building permit. They are also used to determine the price of the project.

General Arrangement Drawing
The general arrangement shows all necessary information: overall dimensions, installation details, overall weight/mass, weight of sub systems, and service supply details.

Arrangement Drawing
Arrangement drawings include information about the self-contained units that make up the system: table of parts, fabrication and detail drawing, overall dimension, weight/mass, lifting points, and information needed to construct, test, lift, transport, and install the equipment. These drawings should show at least three different orthographic views and clear details of all the components and how they are assembled.

Assembly Drawing
The assembly drawing will typically include three orthographic views of the system: overall dimensions, weight and mass, identification of all the components, quantities of material, supply details, list of reference drawings, and notes. Assembly drawings show in detail how certain component parts are assembled.

Detail Drawing
In a detail drawings, components used to build the mechanical system is described in some detail to show that the designer's specifications are met: relevant codes, standards, geometry, weight, mass, material, heat treatment requirements, surface texture, size tolerances, and geometric tolerances.

Fabrication Drawings
A fabrication is made up of many different parts. A fabrication drawing has a list of parts that make up the fabrication. In the list, parts are identified (balloons and leader lines) and complex details are included: welding details, material standards, codes, and tolerances, and details about heat/stress treatments.

Details to Include

 * Size, type, and layout of ducting
 * Diffusers, heat registers, return air grilles, dampers
 * Turning vanes, ductwork insulation
 * HVAC unit
 * Thermostats
 * Electrical, water, and/or gas connections
 * Ventilation
 * Exhaust fans
 * Symbol legend, general notes and specific key notes
 * Heating and/or cooling load summary
 * Connection to existing systems
 * Demolition of part or all of existing systems
 * Smoke detector and firestat re-ducting
 * Thermostat programming
 * Heat loss and heat gain calculations
 * Special condition

Job Outlook
About 80,000 jobs are held by mechanical drafters in the United States of America during 2008. From 2008 to 2018, mechanical drafting hiring rate is expected to neither increase nor decrease. It is encouraged to either take two additional years of training in drafting school after high school or attend a 4-year college/university to develop better technical skills and gain more experience with CADD (computer-aided design).

Income of Mechanical Drafters in 2008

 * Lowest 10% made $29,390.
 * Highest 10% made $71,340.
 * Middle 50% made between $36,490 to $59,010.
 * Median: $46,640.

ADDA-Certification
The American Design Drafting Association (ADDA) has developed a Drafter Certification Test. The test assesses the drafter's skill in basic drafting concepts: geometric construction, working drawings, and architectural terms and standards. The test is administered periodically at ADDA-authorized sites.

Regulations in Canada
Mechanical system drawings must abide to all of the following regulations: the National Building Code of Canada, the National Fire Code, and Model National Energy Code of Canada for Buildings. For residential projects, The National Housing Code of Canada and the Model National Energy Code of Canada for Houses must also be followed. These drawings must also adhere to local and provincial codes and bylaws.