Trane Tracer ZN524, Руководство по диагностике для владельца установки

Страница: 25 / 52

CNT-SVX11A-EN 25
Unit Operation
All other numers will be interpreted as
Auto.
As the controller automatically deter-
mines its heating or cooling mode, it
changes from cool to heat or from heat
to cool, while the error (integrated over
time between the active setpoint and
the space temperature) is (900
°F
• Sec).
Integration only begins once the heat-
ing and cooling capacity is equal to 0%
(See Figure 15).
Heat/Cool Changeover Logic
If the measured space temperature is
69
°F
and the active cooling setpoint is
72
°F
, the error between the space tem-
perature and the setpoint is three
degrees. If the same error exists for one
minute (60 seconds), the integration
term is (3
°F
• 60 Sec) or (180
°F
• Sec).
The Tracer™ ZN524 Unit Controller
changes from heating to cooling and
cooling to heating when the integration
term exceeds (900
°F
• Sec). Along with
satisfying the integration for heating
and cooling changeover, the measured
space temperature must fall outside the
setpoint range. This means the space
temperature must be greater than the
active cooling setpoint or lower than
the active heating setpoint.
Example: If the cooling setpoint is 75
°F
and the heating setpoint 70
°F,
any space
temperature greater than 75
°F
or less
than 70
°F
is outside the setpoint range.
Once the integration term is satisfied
and the space temperature is outside
the setpoint range, the controller
changes modes. However, before the
unit's heating or cooling capacity
ramps up, the controller checks to make
sure it is capable of heating or cooling.
In instances where waterside
economizers or boilerless controls are
in use, it is necessary to verify the
water temperature before unit opera-
tion is allowed.
Figure 15: Heat/Cool Changeover logic