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Siemens
Desigo TRA Engineering, mounting and installation
CM111043en_09
Building Technologies
Electrical features of inputs & outputs
2016-02-22
8.3.3
Triacs and AO 0-10V on DXR2 AC 230 V: engineering
AC 24 V is produced internally.
The max. admissible continuous load for triacs
and field supply is 4 VA
(6 VA during 300 s for the starting load of thermal
actuators in cold condition).
The firmware features the following mechanisms to avoid overload:
Internal prioritization
of commands "AO 3-position", "AO PWM Const. period"
and "AO PWM Thermal" so that only one triac is active at a time. Thus,
two
actuators on two different triacs can be driven simultaneously under
certain conditions.
Alarm "Triac overload"
appears in the output object if a 3-position command is
delayed by more than 15 minutes by the prioritization.
The alarm disappears 15 minutes after the problem ends.
No prioritization
for binary and multistate outputs (BO and MO).
The power supply switches off for 2 s
and on again if the max. load (6 VA) is
exceeded.
Alarm "Current overload"
appears in the triac module device object
and disappears 10 minutes after the overload ends.
The following rules are independent of the source of the input / output command
(the application or an external BACnet reference).
1.
The sum of all simultaneous loads must not exceed 4 VA:
– loads on triacs
– Binary and multistate outputs
– loads on the field supply
A higher field supply load may be covered by an external AC 24 V
transformer. For triacs this solution is not admissible.
2.
2 thermal actuators
(AO PWM thermal 5...50%) may be driven at the same
time with one triac each. In this case the two triacs are activated round robin.
3.
2 motorized actuators
(AO 3-position) may be driven at the same time with
two triacs each. The pulses for the second actuator are delayed.
If the motor power is very small, up to 4 actuators can be driven with the same
two triacs (see examples on next page).
4.
Max. 1 actuator
with function
AO PWM spring return or AO PWM constant
period
. These signals have highest priority. They would delay other
commands much too long.
5.
Multiple motorized actuators (AO 0-10V) on one output
are admissible if
– The sum of the loads on the 0...10 V inputs is <= 1 mA.
– The sum of the max. power of the actuators (delivered by the field supply)
is <= 4 VA (the motor pulses are not staggered).
6. "Max. 4 VA" applies for
heating and cooling devices separately
, if the
application EITHER heats OR cools.
7. "Max. 4 VA" applies for
the sum of heating and cooling devices
, if the
application heats AND cools simultaneously (downdraft compensation).
8.
Binary and multistate outputs
(BO Triac, MO Triac) are not subject to
prioritization. The load must be considered in addition and must be added to
the load of the actuators.
Firmware functions
Engineering rules
