Chapter hvac engineering Fundamentals: Part 1 Introduction

6.6.8
Distribution piping configurations
for water
Three basic system configurations are used: out-and-back, reverse-
return, and loop.
The out-and-back system (Fig. 6.13) is common in large campus sys-
tems. The supply and return mains run in parallel from the central
plant to the points of use, with flow in opposite directions and with
equal reduction in size as flow rates reduce. This means that the point
with the lowest pressure difference from supply to return is at the end
of the main, as shown on the pressure profile (Fig. 6.14). Then the
branches nearest the central plant may require extra pressure reduc-
tion by means of balancing valves.
The reverse-return system (Fig. 6.15) is designed to provide pres-
sure differences from supply to return which are similar at all
Design Procedures: Part 4
Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.

---