Trane Tracer AH540 User Manual

Chapter 4 Sequence of operation
66 CNT-SVX05B-EN
temperature increases above the defrost setpoint + 10°F, an integrating
function is initiated. When the evaporator refrigerant time-temperature
satisfied, defrost operation is terminated. When defrost is terminated, DX
cooling capacity is allowed to once again stage On (see Table 25).
Coil defrost binary input
The controller provides two binary inputs that can optionally be config-
ured for coil defrost, IN7 and IN12. These inputs should be used if the
universal analog input is not available or cannot be configured for evapo-
rator refrigerant temperature.
When the coil defrost binary input is active, the controller de-energizes
the last active DX cooling stage. All subsequent binary outputs will de-
energize; one stage every 120 seconds or until the coil defrost binary
input resets to a normal state.
DX split-system cooling
The Tracer AH540/541 controller provides air-handling-unit, direct-
expansion-cooling sequence of operation for split-system air-handling
units. In order for the control system to operate, the controller must be
properly wired and configured to the condensing unit.
The controller does not provide any lead-lag, condensing unit protection,
condenser fan control, or periodic pump-out control. Pump-out and con-
denser fan control must be coordinated with condensing unit operation
using electromechanical devices.
Compressor stages and circuits
The Tracer AH540/541 controller provides four 24 Vac binary outputs
(BO3 to BO6) for staged DX cooling. Each output is energized sequen-
tially BO3, BO4, BO5, BO6 as cooling capacity demand increases in a
last-On, first-Off method. To optimize the controller ability to manage coil
frost conditions, adhere to the following staging and circuit information
when making wiring connection between the controller and the condens-
ing unit.
For four-stage, two-circuit condensing units connect BO3 to the first stage
of circuit 1, BO4 to the first stage of circuit 2, BO5 to the second stage of
Table 25. Evaporator refrigerant temperature effect on DX cooling
Evaporator refrigerant temperature DX cooling operation
Less than defrost setpoint. • DX cooling outputs will turn Off in sequence according
to a time-temperature function until the refrigerant tem-
perature rises above the defrost setpoint.
Between defrost setpoint and defrost setpoint +10°F. • DX cooling outputs stop unloading.
• Frosted DX cooling outputs will be re-enabled following
a minimum 10 minute defrost time interval.
Greater than defrost setpoint +10°F. • A time-temperature function will enable all compressor
stages.

Trane Tracer AH540 Specifications

General

Brand	Trane
Model	Tracer AH540
Category	Controller
Language	English