RTD-10 relays can (only) be reconfigured either via Modbus or, in the case of inverting relays, with DIP switches. Please see the attached instructions ('RTD-10 Relays Advanced Instructions' and 'RTD-10 - invert relays with DIP switches').
Amongst others the relay outputs can be
- inverted
- Note: The relay output of the RTD-10 is always open circuit when powered down, there is no latching action. The Relay Invert option changes the behavior of the relays only when powered up, so that in the Inverted state, Open Circuit = Fault, Closed Circuit = No Fault. This is a common use of the RTD-10 where power failure is considered a fault condition.
- set to RUN and Fault (instead of Level 1 and Level 2 in Duty/Standby mode)
- set to signal that there is Cooling demand:
- Set Relay 1 function K1 = 6 'Thermo On' and K2 = 8 'Unit ON + in Cool Mode' (Not Thermo Status). Then you need to wire Relays R1 and R2 in series.
- allowed to control the relays via Modbus:
- Set Holding Register H11301=10 (Relay R2: H11302). The Relay R1 will then be controlled from Holding Register H12001 (Relay R2: H12002). You could then externally (via Modbus) read Operation Mode and On/Off status, apply a function that you have defined in your system and then write (again via Modbus) to H12001 (0: R1 open, 1: R1 closed).
To write values to the Holding registers using Modbus the RTD-10 must be set Standard Operation mode (see RTD-10 installation instructions). Thus, if the RTD-10 DIP switches are set to operate in Duty/Standby mode: Change the DIP switches to Standard Operation mode (e.g. Standard Control: Resistance), write the values to the Holding registers and then change the DIP switches back to Duty/Standby Operation mode.
IMPORTANT: The relay registers shouldn't be changed unless really required.
Please note that changing the relay configuration means that the RTD-10 interface configuration has been changed from Standard to Custom. Therefore, at startup of the RTD-10 interface the custom configuration will be signalled by the LEDs as described in figure 19b in the installation instructions (attached).
*Explanation: In the “RTD-10 Relays Advanced Configuration" instructions (below the Relay functions table) 'Thermostat Demand in VRV units is calculated by the RTD-10' means:
In Skyair units Thermostat Demand Indication is generated by indoor unit. RTD reads this information from indoor unit and just signals it. While in VRV units there is no Thermostat Demand Indication generated by indoor unit so RTD calculates this according to current state (current mode, setpoint and temperature).