Mounting
The RTD-LT/CA interface can be mounted on DIN rails, or on a surface using screws of up to 5mm diameter. Do not install it inside the Altherma unit.
Power
The RTD-LT/CA requires a 15V (12 V also possible, but 15 V preferred) to 24VDC power connection (see the power ratings, as well as WARNINGS and CAUTIONS on page 7 of attached installation instructions).
The RTD must be powered from an SELV power supply (Figures 4, 5 of attached installation instructions). Any device connected to the RTD on the RS485 connection must also be powered from an SELV power-supply (Figure 6 of attached installation instructions), or must be connected via a galvanic isolated RS485 repeater with at least 1.25kV isolation (Figure 7 of attached installation instructions). Non-SELV devices must not be connected directly to the RTD (Figure 8 of attached installation instructions).
SELV (Safety Extra Low Voltage): Power supply below 42V supplied through a safety isolating transformer complying with EN61558-2-6.
P1P2 and Wired remote controller
Use the P1P2 terminal to connect the RTD-LT/CA to the unit. Please check in the indoor unit's installation instructions whether it is connected to the terminals X5M 1 and 2 for P1P2 communication.
Please follow this link for information about P1P2 network requirements.
The RTD-LT/CA operates in SUB mode with a EKRUCAL1 remote controller configured as MAIN P1P2 device. See Altherma LT CA instructions for number of controllers that can be connected to P1P2, the RTD counts for 1 BRC controller.
RS485
RS485 Cables must use stranded 24awg shielded or unshielded twisted pair to Cat3, Cat4 or Cat5 specification. Use a twisted pair for connections DB,DA and an extra core for connection GND. Install RS485 cable as shown in figure 2 of the RTD-LT/CA installation instructions. For further details see page 8 of the installation instructions (RS485 Network Installation).
For futher information, please see the article RS485 network requirements.
DIP switches
The RTD-LT/CA offers several operation modes which can be set using the DIP switches. See the RTD-LT/CA installation instructions for details on DIP switch settings.
Hardwired Inputs (S1 - S6)
Parameters can be controlled using the hardwired inputs (S1 - S6). The use of any of the inputs is optional, i.e. if your application doesn't require the use of hardwired inputs then they can be left open.
When using hardwired inputs to set the setpoint: Resistive inputs are accurate to 0.1kΩ, allowing a setpoint to be defined to the nearest 1°C. Voltage inputs are accurate to 0.1V.
Please see the attached installation instructions for further details.
Modbus
The RTD-LT/CA supports the Standard RTU Modbus protocol. Please follow this link for RTD baud rate and parity settings. The RTD-LT/CA Modbus registers are listed in the installation instructions. In case of Sequencer Mode please use the Modbus table documented in the RTD-W installation instructions (see this article: How to install the RTD-W).
Please also have a look at our article Using Modbus with our interfaces.
The RTD-LT/CA only operates as Modbus slave. The Modbus address range is 0 to 63 and is set as shown in figure 9 of attached RTD-LT/CA installation instructions, except for Smart Grid Mode where only Modbus Address 0 to Address 15 is supported (see page 9 of the RTD-LT/CA installation instructions).
Depending on model, certain Holding Register and Input Register functionality may not be available. After a reset, or in cases where functionality is not available for the attached model the register value
will report 32768 : ‘Function not available’.
Please also look at the article RTD-LT/CA: FAQ to Modbus control.
You can also use our free software ModTool to view all the parameters, and by clicking with the right mouse button on a parameter the register's address will be shown.
Please download ModTool attached to this article. For further information regarding ModTool, please click here.
Relays
The relays are normally open and they close when there is a respective signal. The relays are Volt-free contacts (dry contacts) and operate as described in the RTD-LT/CA installation instructions. Please note the allowed power ratings on page 7 of the installation instructions.
Single faults cannot be masked.
Status LEDs
The RTD LEDs signal various statuses during start-up, as well as during operation. For explanation of the LED (LED 1 and LED 2) signals please see page 8 and respective figures in the Installation instructions.
Once communication over P1P2 between RTD-Lt/CA and indoor unit has been established LED 3 should be flashing indicating that information is being exchanged between the RTD and the indoor unit(s).
Fault Signals
Unless otherwise configured (see the operation modes and inputs in the installation instructions) a Fault is signalled by relay R2 . The exact fault code can be read either on the wired remote controller display or via Modbus.
For information on Fault code generation function, please see the article RTD Fault Codes.
For Error code information refer to Daikin Service manual.
Testing
Testing can be performed via hardwired inputs (S1 - S6), as well as Modbus. It can be tested without connecting an indoor unit.
Note that for testing you with Modbus you can use our software ModTool (please download the ModTool version in this article). For information on using ModTool have a look at the article ModTool Communication with our Products.
Note that if the RTD is not connected to any indoor unit then the parameters will be reset to default. When connected to an indoor unit then the values you have set will be stored.