SELECT AND WIRE THE TRANSFORMER TO THE CONTROL PANEL
1. Note:
The HVAC equipment transformer cannot be used
for power. A separate transformer should be used to
power the zone panel, thermostats and dampers.
2.
Wire 24VAC from transformer to the POWER, R and C
terminals (see
FIGURE 7
).
3.
Sizing of transformer to accommodate the number of
dampers:
a.
Select your damper type.
OPTION 1: Normally Open/Power Close Dampers
(2-Wire)
i.
Add up all the zone dampers that are in the system.
ii.
Subtract the number of dampers in the zone with the least number of dampers. This is the greatest number of dampers that could be
energized at one time.
iii.
Multiply this number by 10 to determine the damper VA requirement. Add an additional 10VA for the zone panel and thermostats.
Example:
If you have a 3-zone system, and there are two dampers per zone, then the total number of dampers that could be energized at
one time is,
6 - 2 = 4 dampers
4 dampers x 10VA per 10VA for zone panel and thermostats = 50VA required
OPTION 2: Power Open/Power Close Dampers (3-Wire)
i.
Add up all the zone dampers that are in the system.
ii.
Multiply this number by 2.5 to determine the transformer size. Add an additional 10VA for the zone panel and thermostats.
Example:
If you have a 3-zone system, and there are two dampers per zone, then the total number of dampers that could be energized at
one time is,
6 dampers x 2.5VA per 10VA for zone panel and thermostats = 25VA required
b.
Select a transformer that meets or exceeds the value calculated.
TRANSFORMER
24
VA
C
120
VA
C
90-2116
FIGURE 7
– TRANSFORMER
7
B2206668C 61001213 AA 6202-6203 Zoned Comfort Control Install ENG-wrf.indd 7
6/14/18 3:28 PM
