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Chapter 4 Input/output functions and wiring for typical applications
14 CNT-SVX07C-EN
Binary inputs
The Tracer ZN521 controller includes four binary inputs. Each binary
input associates an input signal of 0 Vac with open contacts and 24 Vac
with closed contacts. You can use the Rover service tool to configure each
of the inputs as normally open or normally closed. If an application does
not warrant the use of a particular input, configure the input as Not
Used. This will disable the generation of diagnostics for this function.
Table 3 gives the function of each binary input.
Each function is explained in the following paragraphs. For an explana-
tion of the diagnostics generated by each binary input, see “Diagnostics”
on page 58. For more information about how the controller operates, see
Chapter 5, “Sequence of operations”
BI1: Low-coil-temperature detection
The function of low-coil-temperature detection is to protect the coil from
freezing. If BI1 is wired to a binary low-coil-temperature detection device
(freeze-protection switch) and a low-coil-temperature condition exists, the
Tracer ZN521 will detect the condition and generate a Low Coil Temp
Detection diagnostic.
BI2: Condensate overflow
The function of condensate overflow is to prevent the condensate drain
pan from overflowing and causing water damage to the building. If BI2 is
wired to a condensate overflow switch and the level of condensate reaches
the trip point, the Tracer ZN521 will detect the condition and generate a
Condensate Overflow diagnostic.
Table 3. Binary inputs
Binary input
terminal label
Function
BI1 Low-coil-temperature detection
BI2 Condensate overflow
BI3 Occupancy or generic binary input
BI4 Fan status
Note:
BI1 applies to hydronic/steam coils only.