Heating Or Cooling Mode; Entering Water Temperature Sampling Function - Trane Tracer ZN511 Installation And Operation Manual

CNT-SVX06B-EN

Heating or cooling mode

The heating or cooling mode can be determined in one of two ways:
By a communicated signal from a BAS or a peer controller
•
Automatically, as determined by the controller
•
A communicated heating signal permits the controller to heat only. A
communicated cooling signal permits the controller to cool only. A com-
municated auto signal allows the controller to automatically change from
heating to cooling and vice versa.
In heating and cooling mode, the controller maintains the zone tempera-
ture based on the active heating set point and the active cooling set point,
respectively. The active heating and cooling set points are determined by
the occupancy mode of the controller.
For two-pipe and four-pipe changeover units, normal heat/cool operation
will not begin until the ability to conduct the desired heating or cooling
operation is verified. This is done using the entering water temperature
sampling function (see "AI1: Entering water temperature sampling" on
page 37), for which a valid entering water temperature is required. When
neither a hardwired nor a communicated entering water temperature
value is present on changeover units, the controller will operate in heat-
ing mode only (assuming the water is hot), and the sampling function is
not used.
For 1 heat/1 cool units that are not changeover applications, whether the
entering water temperature is hot or cold is dependent on the configura-
tion of the unit. For these applications, the entering water sampling func-
tion is not used. The entering water temperature value is used for
information and troubleshooting only and does not affect the operation of
the controller.
Entering water temperature sampling
function
The entering water temperature sampling function is used with two-pipe
and four-pipe changeover units and requires a valid entering water tem-
perature value. If the entering water temperature value is less than 5°F
(2.8°C) above a valid zone temperature value for hydronic heating and
greater than 5°F (2.8°C) below a valid zone temperature value for
hydronic cooling, the sampling function is enabled. When the sampling
function is enabled, the controller opens the main hydronic valve to allow
the water temperature to stabilize. After 3 minutes, the controller again
compares the entering water temperature value to the zone temperature
value to determine if the desired heating or cooling function can be
accomplished.
Heating or cooling mode
51