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When is the indoor climate ”good enough”?
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By Erik Lund Kristiansen, Key Account Manager, Danfoss A/S
A “Perfect” indoor climate can be achieved by installing sensors for measuring and controlling all parameters. Despite this, the solution chosen is often a compromise between the costs and the indoor climate. But why compromise when it comes to the technical solution and thus the indoor climate? |
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The quality of the indoor climate is evaluated on parameters like dust, solar gain, lighting, draft/wind velocities, allergy friendly materials, interior decoration, humidity, room temperature, degree days, wind impact, dimensions of rooms and the number of people/occupants etc. Besides this, it is an important objective to reduce the CO2-emission, and it is a fact that the available fossil fuel deposits decrease, and as they do, the price goes up. This results in high focus on energy “correct” solutions for the indoor climate – both taking the product development, production, installation, commissioning and operation into account.
Comfort Cooling - an important parameter
The demands are high for ensuring an accurate control and a stable room temperature. Typically there is a lot of experience in controlling the heating in each room.
In commercial buildings (like offices, hotels, banks, shopping malls, hospitals etc.) the trend goes towards installation of comfort cooling in each room as a standard. By this means, it is avoided that too high room temperatures influence our wellbeing and our efficiency.
Studies clearly show a relation between oscillating temperatures, too high or too low temperatures and our efficiency.
How the room temperature is perceived is very individual. |  | | This combined with a tendency going towards buildings with large window areas, better insulation etc play a vital part in connection with obtaining a good indoor climate and in relation to the demands on the technical installations and their interaction. | Product development is not only for the visible and tangible parameters but also all the products we do not notice but which still have a big impact on the indoor climate. |
Balancing Valves ensure a precise flow
Danfoss has high focus on developing products which give a more precise control of the room temperature (both by heating and by comfort cooling) together with a reduction of the energy consumption.
 | When a big number of emitters are installed (radiators, fan-coils, chilled beams, air-handling-units, underfloor heating etc) in a building, like a hotel or office building, the individual emitters will often be connected to one common pipe work for heating and one common pipe work for cooling.
Each office should then only have the amount of energy available which is required at that time of the day and maximum the amount of energy which e.g. the chilled beam is designed for.
It is therefore necessary to install balancing valves, which ensure that there never is circulated more energy in the systems than required and that the energy required is available when needed. | | Many resources are used for developing the right products, with the sole purpose of easing the work load in the daily business. | |
Traditionally, this has been done using high numbers of manual balancing valves - ensuring the distribution of energy in the building at maximum or design load – and many of the users found this system ”good enough”… But the fact is that a heating - or comfort cooling circuit is only at design load a very short period of time every year and that pressure oscillations continuously change the working conditions for the manual balancing valves.
If costs should be kept low and the system should stay technically competitive on energy consumption, flexible at system changes and not least the demanded user friendliness, the demands are far higher on these systems with variable flow than manual balancing valves can fulfil.
New relevant technology
New technology and innovative development has led to even better methods for reducing the total energy consumption for a building.
Circulator pumps are controlled according to the actual need by e.g. Danfoss VLT frequency converters and thus the pumping energy is reduced. This reduces the running costs, and in some cases even a smaller pump can be installed reducing the capital costs as well.
The room temperature is often controlled by self-acting or electronic thermostats for controlling the heating together with modern combination valves for the comfort cooling. |  | | Reference project in Dubai |
Modern combination valves combine an automatic flow limiter and a control valve in one valve house. This reduces the total number of valves required to ensure a stable and precise room temperature.
The demands for valves today are typically:
- long lifetime (incl. life-cycle-costs)
- high quality - accuracy
- high user friendliness during commissioning and usage – without the use of tools
- easy to install – reduced number of valves in the total system
- good service from the manufacturer – delivery on time
Special valve for comfort cooling
Danfoss has developed a special valve for comfort cooling. The AB-QM valve complies with the mentioned demands for an improved comfort or indoor climate.
It was the first automatic control valve on the market – which besides ensuring a correct balanced system also has a differential pressure independent control valve, which at all loads has 100% valve authority.
The wide selection of actuators available makes it possible to control the flow with all existing control signals being on/off or modulating (0-10V, 0-20 mA, PWM etc).
When a valve is installed at each emitter (fan-coil, chilled beam, air-handling unit etc), this emitter is secured against receiving too much flow or energy. The valve has an integrated flow limiter, which continuously reacts and counteracts against pressure oscillations thus reducing the amount of water to the maximum design load condition.
The choice of actuator and control system (stand-alone or BMS system) then controls the room temperature and the flow between no flow and the set maximum design flow.
If all emitters are restricted to receive only the design flow disregarding the changes in the pressure conditions, the entire system will be balanced without the use of other valves.
This is a huge advantage in projects implemented in stages. Then the individual valve is just installed as usual at each emitter and set for the design load for the controlled emitter. The building can then be commissioned and taken into use, and any later extensions or alterations do not influence the already existing system. This reduces the total project time consumption significantly and will reduce the running costs.
So the conclusion is that the possibility of creating a good indoor climate does exist also without compromises and without losing the competitiveness of the project economy. |
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As easy as setting your watch
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The Danfoss AB-QM is a control valve that provides superb control and automatic hydronic balance. Due to its intelligent membrane-driven construction the AB-QM replaces 2 valves, a control- and a balancing valve, and dynamically adjusts itself to all loads. With the easy to use setting mechanism the right design flow can be set in just a few seconds which makes creating the perfect indoor climate as easy as setting your watch. |
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