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CNT-SVX06B-EN
Chapter 7
Sequence of operations for
the 1 heat/1 cool
configuration
A Tracer ZN511 zone controller configured to control a 1 heat/1 cool unit
will operate to maintain the zone temperature set point. This chapter dis-
cusses many of the operational sequences used by the controller to accom-
plish this goal.
Power-up sequence
When 24 Vac power is initially applied to the Tracer ZN511 zone control-
ler, the following sequence occurs:
1. All outputs are controlled off.
2. The controller reads all input local values to determine initial values.
3. The random-start timer begins (see "Random start" on page 48).
4. If a hardwired zone-temperature value is not detected, the controller
begins to wait for a communicated value. (This can take several min-
utes [15-minute default] and occurs concurrently with the remainder
of the power-up sequence.) If a communicated zone-temperature
value arrives, normal operation can begin when the power-up
sequence has concluded. If a communicated zone-temperature value
does not arrive, a Zone Temp Failure diagnostic is generated (normal
operation cannot begin without a valid zone-temperature value).
5. The random-start timer expires.
6. The power-up control wait function begins automatically if the config-
ured power-up control wait time is greater than zero. When this func-
tion is enabled, the controller waits for the configured amount of time
(from 0 to 120 seconds) to allow a communicated occupancy request to
arrive. If a communicated occupancy request arrives, normal opera-
tion can begin. If a communicated occupancy request does not arrive,
the controller assumes stand-alone operation.
7. Normal operation begins assuming no diagnostics have been gener-
ated.
47
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