KNX HVAC

Samples of heating, ventilation and air conditioning systems with KNX

Individual room temperature control

Individual room temperature controlzoom

Individual room temperature control offers the possibility of regulating the room temperature of a single room regardless of the temperature in other rooms. To do so, it is however necessary for the temperature in each room to be measured separately. The current controllers are mainly complete, aesthetically sophisticated room controllers which are not only used to measure the temperature and to set values but also to control all the other functions in a room. Some of the current controllers can also measure the CO 2 content and air humidity as well as support the heating and   /   or cooling operating modes. Via the networking of sensors and actuators in the room, the individual room temperature control also offers the option of including the status of presence detectors and window contacts and controlling the room temperature automatically dependent on the respective conditions. In projects that have already been implemented, energy savings of up to 50 % could be achieved with individual room temperature control based on KNX.

 

Radiator and underfloor heating, cooling ceilings

Radiator and underfloor heating, cooling ceilingszoom

In radiator and underfloor heating, the centrally generated energy is transported with water to the required locations in the building via pumps and piping. Valves control the rate of flow in the individual heating circuits and thus the heat emission. Cooling ceilings function according to the same principle, the only difference being that cooled water is transported through the pipes and heat is extracted from the room via the cooling elements. The triggering of the valves is normally carried out via analogue thermoelectric or motor valve drives. Thermoelectric drives are connected cost-effectively to special KNX actuators which usually have multiple channels. Motor valve drives with an integrated KNX interface on the other hand have the benefit that the valves can be very precisely positioned and mostly have additional intelligence and diagnostic functions. Through bidirectional communication, it is furthermore possible to transfer both the current valve position and error messages via KNX.

 

Fan coil controllers

Fan coil controllerszoom

The term “fan coil” means a convector fan which is typically used for cooling rooms. Applications are also possible in which the fan coil unit is used for heating or ventilation. Traditionally, a fan coil unit comprises a fan and a heating or cooling register (coil). The centrally produced cooling or heating capacity is routed through the building via the piping system and retrieved by each unit as required. As a general rule, one fan coil unit is installed per room. A benefit of fan coil control is the rapid availability of thermal energy or cooling capacity. It is therefore widely used in hotels and office buildings.
It is possible via KNX to separate the unit and the operation cost-effectively in terms of rooms. The control of the fan and the heating or cooling register is carried out via special KNX fan coil actuators in the unit while the operation is usually carried out via KNX room thermostats with extended functions and setting options.

 

Interfaces to energy generation and distribution systems

Interfaces to energy generation and distribution systemszoom

With interfaces to energy generation systems such as condensing boilers (oil, gas, zeolite), heat pumps as well as solar thermal and photovoltaic systems, system operators have the option of finding out about the current state of their heating system using the KNX visualisation system, predefining setpoint values and setting operating modes. Fault signals are automatically transmitted to KNX and displayed so that the appropriate measures can be taken before any damage occurs. As the current heat requirement in the rooms can be communicated in most cases via the KNX gateway to the heating controllers, the heat generation must be precisely matched to the current demand.

 

Variable volume flow controller

Variable volume flow controllerzoom

With the variable volume flow controller (VAV), a centrally produced air flow is routed to the rooms and areas in which the air conditioning is regulated. The control of the amount of air and heat is carried out via flaps in the piping system. In most cases, the variable volume flow controller is decentralised and installed separately for each room so that only the required amount of energy is used to maintain the respective indoor room climate. Based on the recorded room conditions and the current air requirement, energetically intelligent and demand-controlled systems can be set up with KNX. A central control unit permanently monitors the flap positions of the individual VAV boxes via KNX. If the flaps destroy excessive inlet pressure, this is reduced. It is the aim to operate the system with the lowest possible pressure loss.

 

Room air control and interfaces to ventilation systems

Room air control and interfaces to ventilation systemszoom

To minimise the energy losses, new buildings are built increasingly airtight. If the natural ventilation no longer exists due to the design, monitored ventilation and extraction is required as otherwise consequential damage to people and buildings may arise and the occurrence of mould, spores and bacteria may be encouraged. When using automated ventilation, additional parameters such as the maintenance of limit values for the CO 2 content, the air humidity and the room temperature are taken into account. With active monitored ventilation and extraction, a central ventilation unit blows fresh air into the building/rooms. On the room side, the “consumed” air is extracted and discharged. With the optional heat recovery, the thermal energy is extracted from the discharged air e.g. via a cross-flow heat exchanger in order to warm up the “fresh” air with it. With this process, heat exchangers inside a building such as lighting, computers etc. can also be used for heating which contributes to an increase in energy savings. In addition to the baseline values, the values for the room temperature, air humidity and carbon dioxide content measured by the KNX individual room controllers and air quality sensors can be transferred via the KNX interfaces to the ventilation system and taken into account during the control. In the other direction, the ventilation system transfers status signals to KNX which for example signal the necessary replacement of ventilation filters. 

 

Interfaces to distributed air conditioning systems

Interfaces to distributed air conditioning systemszoom

Distributed air conditioning systems with split or monobloc devices form an individual concept for flexible room usage. In the case of split devices, the compression of the refrigerant is carried out outside while the air delivery, filtering and temperature control is carried out in the room that is to be cooled. In the case of monobloc devices, all the components are located in a single device indoors. The disadvantage is that the compressor is located in the room and represents a considerable source of noise compared to a split device. Moreover an exhaust hose is required to carry the warm air outside. The interfaces to the air conditioning systems are versatile. In addition to a few standardised interfaces, the manufacturers use a variety of proprietary hardware and protocol solutions. In spite of the variety of interfaces, special KNX gateways enable the integration of almost all the air conditioning devices into KNX.