Chapter hvac engineering Fundamentals: Part 1 Introduction

4.3.4
Heating equipment
Source heating equipment includes central plant boilers for steam and
high-, medium-, and low-temperature hot water; heat pumps, both
Design Procedures: Part 2
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Design Procedures: Part 2
87
Figure 4.1
Single-zone draw-through air-handling unit.
central and unitary; direct-fired heaters; solar equipment, including
solar-assisted heat pumps; and geothermal and heat reclaim. Fuels
include coal, oil, natural and manufactured gas, and peat. Waste prod-
ucts such as
refuse-derived fuel
(RDF) and sawdust are also being used
in limited ways. Electricity for resistance heating is not a fuel in the
combustion sense but is a heat source. Heat reclaim takes many forms,
some of which are discussed in Chap. 10.
Self-contained package AHUs use direct-fired heaters—usually gas
or electric—or heat pumps. For other systems, some kind of central
plant equipment is needed. The type of equipment and fuel used is
determined on the basis of the owner’s criteria, local availability and
comparative cost of fuels, and, to some extent, the expertise of the
designer. Large central plants for high-pressure steam or high-
temperature hot water, may present safety problems, are regulated by
codes and require special expertise on the part of the designer, con-
tractor, and operator. New buildings connected to existing central
plants will require the use of heat exchangers, secondary pumping or
condensate return pumping, and an understanding of limitations im-
posed by the existing plant, such as limitations on the pressure and
temperature of returned water or condensate.