Trane Zone Controller Binary inputs, BI1 Low-coil-temperature detection, BI2 Condensate overflow

Chapter 4 Input/output functions and wiring for typical applications

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.

Table 3. Binary inputs

Binary input	Function
terminal label
BI1	Low-coil-temperature detection
BI2	Condensate overflow
BI3	Occupancy or generic binary input
BI4	Fan status

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

Note:

BI1 applies to hydronic/steam coils only.

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.

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