Auto-Zone Control Systems Auto-Zone Plus Systems Installation & Operation (Version 03A) - Manual (Page 20)

Section 1 Auto-Zone Plus
1-16 Design Guide
It is important to recognize that all buildings have some purely internal zones, such as
Zone 10, which may contain separate offices/conference/computer rooms. These internal
zones will normally have high cooling requirements year around while external zones
(1,2,3, etc.) could be at or near design heating load requirements during the winter
months. This diversity can be used (if properly zoned with multiple HVAC units serving
similar loads and zones) to save energy. However, a single HVAC unit is used to serve
zones with opposed cooling and heating demands as shown in Figure 1-3 the resulting
system will be very energy inefficient and comfort levels in the building will not be
satisfactory.
1
2
3
5
6
7
8
9
10
4
Figure 1-3: Incorrect Zoning of Typical Building
As previously mentioned, Figure 1-3 shows a misapplication of an Auto-Zone Plus (or
any heating/cooling changeover) system. Supplemental heat could be added to the
perimeter zones and controlled with the auxiliary heat control board from the Zone
Controller which would improve the performance of the system but still would not be
ideal. System performance would still generally be compromised and frequent
changeover from the heating to the cooling mode will occur during the heating season if
purely internal zones are combined on the same air-conditioning unit serving perimeter
zones.