• Control of a mixing group
  • Control of a mixing group

Control of a mixing group

HVAC applications and control

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More and more often in systems designed for room heating, cooling and ventilation there are simultaneously heat exchange, air handling or air renewal terminals with different operating principles (such as radiators, radiant floor or ceiling panels, fan-coils, dehumidifiers, mechanical ventilation units with integration of the sensible contribution for cooling, etc.) that make it necessary to produce heat transfer fluid at different temperatures. This can be done directly in the boiler room or locally, by controlling a mixing group.

Ekinex devices Other system components
A) Mixing group controller EK-HH1-TP 1) Mixing group
B) NTC temperature sensor (external) EK-STE-10K-3435 2) Mixing valve with servomotor
C) NTC temperature sensor (immersion) EK-STI-10K-3435 3) Circulating pump (mixed zone)
D) NTC temperature sensor (immersion) EK-STI-10K-3435 4) Circulating pump (unmixed zone)
  5) Boiler room manifold (flow)
  6) Boiler room manifold (return)
  7) Thermal generator (warm fluid)
  8) Thermal generator (cold fluid)
Control with Ekinex

The unmixed zone directly serves the heat exchange terminals with heat transfer fluid at the temperature produced in the boiler room. The EK-HH1-TP unit (A) controls the mixing group (1) by adjusting the flow temperature of the heat transfer fluid for the mixed zone.

For this purpose, the mixing valve (2) equipped with a servomotor and the circulating pump (3) of the mixed zone are controlled, measuring the flow temperature by means of an immersion sensor (C). Optionally, it is also possible to measure the return temperature by means of a second immersion sensor (D).

The outdoor temperature sensor (B) measures the outdoor air temperature for climate compensation control. In the case of radiant panel systems also used for summer cooling, the ideal use of the controller (A) is in combination with a maximum of 16 room thermostats EK-EQ2-TP equipped with temperature and relative humidity sensors to have an effective integration between the boiler room regulation (primary) and the room or zone control (secondary). In this way, the system on and off as well as the optimal flow temperature of the heat transfer fluid are automatically selected according to the actual internal conditions of the building; in cooling mode it is also possible to select the optimal flow temperature with active protection from condensation.

Control options Heating Cooling
Fixed point
Climatic compensation
Adjusting to internal conditions -
Adjusting to return temperature -
Climatic compensation and adjusting to internal conditions -
Adjusting to internal thermo-hygrometric conditions -
Climatic compensation and adjusting to internal thermo-hygrometric conditions -
Focus on the EK-HH1-TP mixing group controller

The EK-HH1-TP controller (A) is a KNX device, fully programmable via ETS, which allows the flow temperature of the heat transfer fluid to be regulated in heating and cooling hydronic systems.

The device can be used as a stand-alone unit or in combination with one or more ekinex® room thermostats to create single-zone or multi-zone systems (up to a maximum of 16 zones), controlling the servomotor of a 3-point floating mixing valve, powered at 230 Vac or 24 Vac, or with 0-10V signal and controlling the circulating pump of the mixed circuit in run / stop mode.

The device manages over-temperature (in heating) and under-temperature (in cooling) alarms. The controller has a backlit LCD text display, four membrane buttons for navigating through the display menu and two LEDs for alarms and switching to manual mode. The display allows the operating parameters to be monitored; some control parameters can also be modified with respect to the initial configuration carried out with ETS. The switchover of the system conduction mode (heating / cooling) can be done from the bus, from a digital input (configured for this purpose) or manually from the front keyboard. Alarms from anti-condensation probes can be managed. The digital outputs, not used to activate a circulating pump, can be configured to control a zone valve servomotor located on a circuit dedicated to fan-coil units or dehumidifiers.

To create automation logic, the device is also equipped with 2-channel logic functions (16 inputs per channel) with exclusive AND, OR, NOT and OR blocks and delayed activation of the corresponding output.

Inputs and outputs
Terminal no. Label Connection
3-4 IN1 Input 1 (fl ow temperature sensor)
5-6 IN2 Input 2 (return temperature sensor)
7-8 IN3 Input 3 (outdoor temperature sensor)
9-10 IN4 Input 4 (confi gurable as AI or DI)
11-12 IN5 Input 5 (confi gurable as AI or DI)
13-14 A01 0-10 V control output for servomotor
15-16 POWER AUX TRIAC power supply (230 Vac o 24 Vac)
17 CLOSE Control output for servomotor (closing)
18 COM Control output for servomotor (common)
19 OPEN Control output for servomotor (opening)
20-21 D01 Relais output circulator input
22-23 D02 Relais output (additional functions)
24-25 D03 Relais output (additional functions)
Switching the seasonal conduction mode

The seasonal (heating / cooling) mode can be switched in three ways:

  • from the KNX bus;
  • via the front keypad of the controller;
  • by means of a switch connected to an input of the controller.

If switching from the KNX bus is selected, the controller receives the conduction mode from another bus device (via a communication object), such as an ekinex® room thermostat, which has been assigned the master function for seasonal switching.

Switching can be carried out manually using the keypad and the display on the front of the device: in this case, it is the EK-HH1-TP controller that performs the master function of seasonal switching for all Ekinex devices (sensors, actuators) that are on the same system or part of a system served by the controller.

Switching via a switch connected to input IN5 (configured as DI) is suitable for standalone applications in which there is no need for integration between the boiler room (primary adjustment) and the rooms or zones (secondary adjustment).

The switch can be the same as the external selector used in the boiler room for switching the operation of heat generators or shut-off valves of fluids. The current operating mode is stored in the non-volatile memory of the controller.

 
Activating the mixing group
The mixing group can be activated in three ways:
 
  • from the KNX bus;
  • from a controller input;
  • from a controller input and the KNX bus.

By selecting the activation from the KNX bus, the controller connects in logical OR the flow requests coming from a maximum of 16 Ekinex room thermostats. To activate the mixing group it is sufficient that a single room thermostat requires flow.

The activation from an input is suitable for stand-alone applications in which there is no need for integration between the boiler room (primary adjustment) and the rooms or zones (secondary adjustment). A time programmer can be connected to input IN4 to activate the group according to scheduled time slots or the request of a standalone room thermostat.

In systems with distribution manifolds, the limit switches of the electrothermal drives mounted on the individual valves can be connected in parallel.

An intermediate solution, on the other hand, involves activation both from the binary input and from the KNX bus. The input can have priority over the flow requests coming from the zones via bus (for example an external time zone programming device) or it behaves as an additional zone (without priority).

In all cases it is possible to set an activation delay (from 1 to 255 seconds) for the start of mixing; in fact, it is advisable to wait for the electrothermal drives to bring the valves into the open position to prevent the circulating pump from exerting pressure on hydraulically closed circuits.