144 Chapter 6
Mechanical systems deal with the heating and cooling of buildings or spaces. The two primary meth-
ods of heating and cooling use air or water. In an all-air system hot or cold air is transported to the space
with supply and return air ducts. A typical example is a residential forced-air furnace. The furnace uses
gas or oil to heat the air. The air is forced through the ductwork by an electrically powered fan in the fur-
nace. A separate air-conditioning unit is installed for cold air. For most commercial buildings, a large unit,
often located on the roof, powers the all-air system. Supply-air ductwork, registers, and return-air grilles
are required in all spaces within the building.
An all-water heating system uses a type of coil through which hot water is circulated. The most com-
mon example is the fin-tube radiator found in older homes, typically located in front of a window. Today
the most common system is the radiant floor heating panel.
An all-electrical heating system uses electricity to heat elements within a radiator. The most com-
mon is the baseboard heater. It is used when a furnace is not installed. For example, many small cot-
tages use baseboard heaters. Smaller, older commercial buildings rely on a baseboard installation. This
system can also be found in larger commercial buildings as an addition to other systems. An electric ra-
diator with a built-in fan might be located at an exterior entrance door to provide extra heat on the inside.
The mechanical drawings provide the client, the builder, and the permit department with the com-
plete HVAC layout for the job. These drawings are typically part of the construction-drawing set. They are
submitted with the construction drawings for a building-permit application (Figure 6.17). They are also part
of the package for pricing the project. They are used for construction. All ducting, venting, exhaust fans,
and heating and/or cooling units must be supplied and installed as per the approved drawings.
A mechanical-engineering consultant produces the mechanical drawings. Often the same person or
company will produce the electrical and plumbing drawings. These drawings must comply with the var-
ious building codes including all provincial and local codes.
Generally, the engineer uses these plans and incorporates his/her ducting layout. Diffusers, return-
air grilles, and exhaust fans are drawn in as symbols. Heating and/or cooling systems are specified and
their location indicated. Legends, schedules, details, and notes specific to the project are added.
On small projects, all information required is covered on one or two drawing sheets. For large or
complex projects, many drawing pages are necessary to cover all areas of the project.
Typically, the engineer’s drawings must note the type, location, and number of heating and/or air-
conditioning units. HVAC and electrical connections are specified, as well as any connections to gas
lines or water systems. The thermostat type, location, and number are also noted. Figure 6.18 shows a
refrigerant-piping detail diagram
Many projects require that heat-loss and heat-gain calculations be provided. Air-balancing informa-
tion or air-distribution-device schedules are usually included. The information required depends on the
type of project being built.
Many cities and towns have energy-conservation regulations. The engineer’s drawings must abide
by all codes and bylaws pertaining to the city, town, or province where the project is located.
The following are typically included in a set of mechanical drawings:
- Plans showing the size, type, and layout of ducting
- Diffusers, heat registers, return-air grilles, and dampers
- Turning vanes and ductwork insulation
- HVAC unit types, quantities, and location
- Thermostat types, quantities, and location
- Electrical, water, or gas connections