Two-position valve operation
CNT-SVX06B-EN 53
Two-position valve operation
The Tracer ZN511 zone controller will control hydronic, two-position
valves for any of the 1 heat/1 cool applications shown in Table 12.
The controller opens and closes the appropriate value to control the zone
temperature at the heating set point in heating mode or at the cooling set
point in cooling mode.
Two-pipe operation
For two-pipe applications, the Tracer ZN511 can be configured as heating
only, cooling only, or heat/cool changeover (see Table 12). The main coil
can be used as the primary heating source and/or the primary cooling
source. If present, an electric heating element can only be used as the pri-
mary heating source, not as a second stage of heating. A changeover unit
requires a valid entering water temperature value—either communicated
or hardwired—to operate properly. The entering water temperature
value, along with the entering water temperature sampling function,
allows a changeover unit to accurately and reliably control zone tempera-
ture. When there is not a valid entering water temperature present for a
changeover unit, the controller will operate only in heating mode and the
water will be assumed hot.
Four-pipe operation
For four-pipe applications, the Tracer ZN511 can be configured as heat/
cool or heat/cool changeover (see Table 12). The main coil can be used as
the primary cooling source or the primary heating/cooling source. The
auxiliary coil can only be used as the primary heating source, not as a sec-
ond stage of heating. During normal operation, the controller never uses
the main coil and auxiliary coil simultaneously. A changeover unit
requires a valid entering water temperature value—either communicated
or hardwired—to operate properly. The entering water temperature
value, along with the entering water temperature sampling function,
allows the changeover unit to accurately and reliably control zone tem-
perature. When there is not a valid entering water temperature present
for a changeover unit, the controller will only operate in heating mode
and the water will be assumed hot.
Table 12. Configuration options for 1 heat/1 cool applications
Application Main coil
Auxiliary
coil
Electric heat
option?
2-pipe cooling only Cool N/A Yes
2-pipe heating only Heat N/A No
2-pipe heat/cool changeover Heat/Cool N/A Yes
4-pipe heating and cooling Cool Heat No
4-pipe main coil changeover Heat/Cool Heat No
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