CHAPTER 3
HVAC DELIVERY SYSTEMS
OVERVIEW
Section 3.1 introduces the range of system options available, from single package units to
central plants, emphasizing that all systems, regardless of size, work by one or a
combination of two principles—vary the temperature and/or the quantity of air supplied
to a space.
Sections 3.2 and 3.3 are an overview of HVAC controls. The term “zone” is explained in
its strict HVAC context. Understanding “zoning” is key to a good working knowledge of
HVAC design and should be stressed in class. Basic control systems and hardware is
introduced in Section 3.3. In teaching this material, the author finds that posing a series
of questions is useful. First, what variable are we trying to control (temperature or
humidity or airflow, etc.)? Then, how do we measure, or sense, the variable? Finally,
what must happen in the system to affect the variable? These questions, in conjunction
CHAPTER 3
HVAC DELIVERY SYSTEMS
QUESTIONS AND ANSWERS
3.1 Describe the basic difference between interior and perimeter space with
respect to HVAC loads.
3.2 What principles are used to vary the amount of HVAC service to a space with
varying loads?
Systems vary HVAC service by three methods:
3.3 What is an HVAC zone, and how might a zone differ from a room?
3.4 Name the HVAC delivery systems, which are most flexible for adding or
rearranging zones. Why are they effective in this respect?
3.5 Which HVAC delivery systems are best for preventing high humidity in spaces
and why?
3.6 Which HVAC delivery systems are generally avoided due to high-energy
usage?
3.7 Which HVAC delivery systems are most energy efficient and why?
3.8 Which HVAC delivery systems would be most appropriate in a building for
which risk of water damage is a serious concern?
3.9 Which HVAC delivery systems would be most appropriate in a building in
which intrusion for maintenance within occupied spaces must be kept at a
minimum?
3.10 Of all the HVAC delivery systems discussed in this chapter, which is the most
energy efficient and why?
3.11 Describe the major difference between electric or pneumatic control and
direct digital control.
3.12 When is it appropriate to use two-position control?
3.13 When is it appropriate to use proportional control?
3.14 A hotel developer is deciding whether to use fan coils or PTAC units. How
would you counsel him on matters of cost and quality?
3.15 You’re helping an owner to decide on systems for his new office building. For
perimeter offices, he will either use VAV reheat or VAV with perimeter
convectors. His contractor will provide either system for the same cost. How
would you counsel him on matters of cost and quality?
3.16 You’re helping an owner to decide between VAV terminals and FTU terminals
for interior conference rooms in his new office building. How would you
counsel him on matters of cost and quality:
3.17 Why would you recommend the extra construction cost of a four-pipe fan coil
system vs. a two-pipe fan coil system?
3.18 What is the primary energy advantage of using radiant cooling?
3.19 How are water source heat pumps and PTAC units similar? How are they
different?