Heat recovery with TDA systems

In most cases it is virtually impossible to reach a constant heating temperature in rooms with high ceilings without the support of mechanical appliances. Continuously feeding more fuel is not the best solution as thermal energy is lost in extreme ceiling heights. Due to an increase in costs for energy over the past few years they also cause enormous heating costs and an unfavourable eco-balance. And yet the thermal upthrust can be reversed quite easily: Modern TDA systems meet the requirements in “above“ average rooms and facilities and represent an energy-efficient option to preserve warmth.

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  • Difference in temperature – a problem in rooms with high ceilings
  • Heat recovery with conventional fans and its limits
  • What does TDA mean and how does the system work?
  • Application of a TDA system
  • Enormous savings
  • Short summary 

Difference in temperature – a problem in rooms with high ceilings

Around the upper part of indoor climbing facilities you get the chance to experience the temperature difference – though it might not always be pleasant. 

The systems engineering of heat recovery is based on a simply law of physics: Heated air has a lower density and therefore a lower weight than cool air. Thus warm air rises upwards and builds up underneath the ceiling in enclosed rooms. You are probably familiar with the result: The radiator is turned on but the floor and the level of the seating furniture just stay cold, and the warm cosy air is only noticeable towards the ceiling – unfortunately, that is not where residents dwell most of the time! In rooms with low ceilings the effect might not be all too drastic, warm and cold layers of air meet in the middle of the room and can circulate around each other.

In premises with high ceilings such as old buildings or big assembly hangars this is not achieved so easily and warm air develops in a cushion of heat. This effect is further reinforced if the area is ventilated by open windows or a ventilation shaft. Infiltrating cold air immediately sinks to the ground and pushes warm air upwards or out the window. That means lower and centre areas of the space are hard to warm up even though a great heat output is provided by radiators. Therefore it will always be much colder near the ground than in the upper level.

The drawbacks of heat build-up actually comprise more than just unequal room temperature. The increased moisture content in warm air acts as a promotor for mould growth – that is particularly annoying in warehouses and storage rooms with sensitive foodstuffs or goods. Not only perishable foods, but also textiles, documents and some metals lose market value due to damage caused by humidity. Finally, the ecological significance and recalculation of heating costs send wasted heating energy off the field.

Heat recovery with conventional fans and its limits

When using a room in domestic or professional environments, it is usually the temperature on the ground and the centre of the room that counts. Ceiling fans are ideal for pushing down ascending warm air. They work against the principle of heat layers and allow for a more efficient heating: instead of turning up the radiator even more, the existing heat energy is simply “recycled“. Ceiling fans offer you the benefit of heat recovery during their forward and reverse mode: Forward direction (summer mode):
The conventional running direction “summer mode“ recirculates warm air on the ceiling back to the ground in a vertical direction, distributing it in the room through the rotation of the blades. This type of air movement however is only suitable for rooms with ceiling heights measuring 2.80 m and above. Otherwise the result will have a draughty, cooling effect that fans are known for.

⇒ Even if the indoor air can be spread with conventional ceiling fans, it can be useful to install special TDA fans in rooms with high ceilings such as warehouses, production facilities, gyms, to name a few. These fans are equipped with sensors and transport warm air in the room from the ceiling to the ground. Their powerful motors circulate the air and spread it throughout the lower third of the room to promote heating.

Reverse direction (winter mode):
Reversing the running direction together with the corresponding alignment of the rotor blades allows the fan to suck in cold air from the ground and guide it along the ceiling and the walls until it hits the ground again. During this mode the airflow blends with the warm air on the ceiling, resulting in the temperature difference to even out. This type of heat recovery is a great solution for homes with low ceilings – (unpleasantly cool) draught-like effects are not generated! However, heat recovery with the help of the reverse function only makes sense in rooms with just about 2.60m (maybe 2.80m). A domestic appliance does not come with a motor that is able to create an airflow powerful enough to cover the distance and reach the floor. Light air molecules already begin to rise upwards in the centre region of the room and therefore stay at the top. They would not even reach the cold floor – a true loss for freezing feet.

What does TDA mean and how does the system work?

TDA is an abbreviation for Temperature-Difference-Attenuation system. They operate based on the concept of frequent heat exchange: During the thermodynamic process cooler and warmer layers of air start to blend as their heat energies adjust to each other. Thanks to modern sensor technology TDA systems automatically regulate temperature in the room, no action is required on your part.

Benefits of a TDA system compared to conventional fans
The obvious benefit: TDA ceiling fans start operating automatically once they register an uneven temperature distribution and then stop as soon as the distribution is even again. A check, confirmation or even presence of a human is not required. A standard fan needs to be switched on and off manually. However the owner (if he is present!) is not able to sense the generated layer of heat as quickly as precise TDA sensors. Specific operational intervals also result in saved operating costs.

TDA sets in combination with special fans are installed on the ceilings in high-ceilinged rooms. By means of a LCD (liquid crystal) radio remote control the installed fans can be preset easily. The system helps optimise the exchange of warm and cold air, thus efficiently improving heating in high-ceilinged rooms. The special temperature sensors of the TDA system measure the difference between the colder and warmer layers of air in the room and individually regulate the rotation speed that is required for an ideal exchange of warmth. Differences as small as two degrees are taken into account by modern TDA systems, hot spots caused by overheating are prevented efficiently.

Application in domestic environments

A TDA system for an entire apartment or house makes sense if you are looking to ensure a fully automated temperature balancing in all rooms. A central controller unit monitors and intuitively controls temperature sensors in the different rooms. In case the temperature in a room changes noticeably due to heat build-up the rotation speed of the particular fan is automatically adjusted. That way the TDA set guarantees an ideal heat exchange inside every room of the house. It is also possible to use the system to switch individual fans on and off in different rooms. For instance it is possible to operate the fans only if the room is currently being used. Thus, the TDA system does not only save heating costs but also optimises the power consumption of the fans.

During the summer months the TDA system can be adjusted manually to provide cooling. The controller can be used like any normal wall switch to control the speeds. Hence, you are able to use the fan all year round. The unobtrusive, straightforward design of the Nordik TDA range comes with three blades, a classic white colour and many years of benefit. The Vourdries models are also compatible with TDA modules. These fans are available in white, black and silver and are suitable for use in industrial and commercial environments (no IP rating).

⇒ Detailed information about our TDA systems is available in our category text.

Application of a TDA system

TDA fans come into play whenever common fans are simply too weak: In high residential and professional environments with more than 2.60m ceiling height. Even assembly halls with more than ten metres height are no challenge for these devices. Bigger areas are ventilated by several fans that are controlled by a single regulator.

We recommend TDA fans for:

  • warehouses
  • sales- and showrooms
  • workshops
  • gyms and recreational facilities
  • cultural function rooms
  • rooms in old buildings or mansions with a ceiling height above 2.60 m (8.5 ft)
  • wherever automated ventilation is required

The most important factors for a successful application of ceiling fans for heat recovering purposes are room height and the base area of the room. The diameter of the fans needs to be coordinated individually with each room so that the heat sensors can determine the temperature, and control and regulate the heat exchange. The positioning and the distance between the fans need to be kept in mind to cover the entire space.
⇒ Go to our category text quantity of fans (calculation of size) for TDA systems

Enormous savings

Don’t let it got to waste – save heating costs! 

Increasing commodity prices over the past few years result in proportionally increasing heating costs. No matter if it is oil, gas or electricity – the additional demand for energy in rooms with high ceilings cost a pretty penny. A TDA system is able to stop skyrocketing expenses. The intuitive measurement of the indoor temperature and the resulting ideal exchange of temperature help reduce energy used for heating, because even a small amount of energy provides sufficient warmth. If the size of a fan within a TDA system is coordinated properly with the size of the room heating costs can be reduced by as much as 30 percent during the winter. Even in newly erected buildings with state-of-the-art heat insulation more than 20% can be saved! A study of the University Stuttgart has done extensive research in two identical facilities: one of them equipped with a TDA system, the other one without any installation of this kind. Operational costs of a ventilation system that is already set up in a building can be cut noticeably with automatic TDA systems.

Yet, do not only think about measurable savings in terms of electricity, fuel, etc. but also the prevention of renovation work and loss in value due to humidity and temperature difference that both promote mould growth. On another note, living comfort at home and a more pleasant atmosphere for guests in commercial environments respectively is improved greatly. You and your guests are guaranteed to feel better in a room with consistent conditions – a great number of benefits compared to the relatively low initial investments in a TDA system.

Short summary

In rooms that are used for residential or commercial purposes: high ceilings lead to increased heat requirements. During the winter months the requirement is met by constant heating, due to its nature warm air rises towards the ceiling. The lower areas often stay cold – despite a working radiator. Apart from inconvenient heating costs the generated difference in temperature can heavily impact delicate edibles and other stock. In rooms with less than 2.6 m ceiling height ceiling fans can be run in the reverse direction (winter mode). Their blades are angled in a special way that allows them to push warm air down to the floor area. The exchange of air mass sets a thermodynamic law in motion: energy balancing until the indoor temperature is completely uniform.

On the other hand, if the distance between the ceiling and lower area of the room is too big, the airflow dies down halfway. Temperature difference balancing systems are more powerful than conventional ceiling fans and can recirculate air from ceilings that are much higher than 2.60 m. Even halls with dome constructions above ten metres can be ventilated sufficiently by TDA models. Another benefit is the fully automated operation that does not require any human supervision. The system measures the difference it temperature with sensors that are positioned in the upper and lower “air level“. Once they detect unfavourable developments, the controller unit reacts by starting up the TDA ceiling fan. The running of the fan ceases automatically once the measured values are at an acceptable level again and starts as soon as the sensors register a shifting in temperature. That means the TDA fan operates precisely when it needs to and only then – another reason why TDA models are superior to conventional units in terms of efficiency and capacity. The low costs for installation and operation of a TDA system pay off quickly: You attain up to 30% savings for heating costs, during summer you can use it to cool the place. In a nutshell, those benefits of just one single system speak in favour of TDA devices!

Whether you heat with crude oil or a fireplace does not matter for the application of TDA devices. The technology can even be used to support ventilation system that already exist and for centralised heat recovery. In spacious halls several TDA fans should be used for better results. Further detailed information is available in creoven‘s TDA category description, you can also find a sample calculation about heating costs in halls in our blog.

Image sources:
Indoor climbing © frantic01010 - fotolia.com
Mechanic © industrieblick - fotolia.com
Stacked coins © stevepb - pixabay.com, CC0 Public Domain