KaRo Systems - KaRo and SARS
 

1) Basic concept of KaRo air conditioning


The office latent load is handled by the outdoor fresh air A.H.U equipped with a heat recovery system, while the space sensible load is handled by the KaRo Mats.


Since the office or patient room latent and sensible demand change independently. The result is a proper humidity control in the room.


2) The fundamentals of good indoor air quality


Over the years, man has built increasingly elaborate houses to protect himself from the rain, heat and cold. Ironically, in many cases, the buildings which we build to protect us may actually be trapping us in a chemical and microbiological mix that can threaten our health the recent Sars epidemic is a good example of danger of recycling air in a building.


Today, studies are showing that the indoor air in Singapore buildings can be up to 10 times more polluted than the outdoor air. This along with the fact that most people in Singapore spend up to 80% of the their time indoor, point to the fact that the KaRo Systems with 100% fresh air is the solution to adopt to have the best indoor air quality.


How does the ASHRAE standard 62-1989 apply?


ASHRAE (American Society of Heating, Refrigeration and Air conditioning Engineers) Standard 62-1989 Ventilation for Acceptable Indoors Air Quality established the standard of care for the design of building. As a peer-generated and reviewed standard the provisions of ASHRAE standard 62-1989 represent the consensus of the HVAC industries and is therefore viewed as a minimum criteria which a prudent design professional would exercised when designing a ventilation system.


In addition ASHRAE Standard 62-1989 recommends that "Relative humidity" in habitable spaces be maintained between 30 to 55% to minimize the growth of allergenic and pathogenic organisms. Indoor relative humidity leaves above 60 % promote the growth of mold and mildew which causes unpleasant odors and triggers allergic reactions in some people and even serious illness.


The graphic below depicts the ASHRAE recommended RH range and KARO recommended use of his system for best efficiency.
 
 

KARO advocates full compliance with. ASHRAE standard 62-1989 (or local codes if more stringent) and considers it the minimum requisite for ventilation.


Why we need to manage Relative Humidity in office and in Hospital


Microbial contamination is a leading cause of occupant complaints and I.A.Q problems today. Uncontrolled indoor relative humidity levels can adversely impact on occupant comfort. ASHRAE standard 55-1992 thermal environmental conditions for Human occupancy, specifies the optimum indoor relative humidity (RH) comfort range as 25 to 55%. In KaRo systems and in a cooling ceiling in general the temperature of the entering ceiling "cooled" water as always to be 1°C above dew-point.


The constant volume system dehumidification challenge.


Constant volume (CV) systems deliver a constant volume of air flow to the office space at a temperature that varies in response to the thermal (sensible load) requirement of the space. Basic psychometrics dictate that in order to reduce the space relative humidity, the fresh air supply must be drier ( at a lower dew point) than the air within the space. At high space sensible loads, the cooling coil Leaving Air Temperature (LAT) is low, usually below the space target dew point, resulting in adequate dehumidification.

However, when the space sensible is low (part load at night) the unit controller respond by reducing the air flow by half. (Two speed fresh air A.H.U and by stopping the cooling ceiling).



3) KaRo Radian cooling


Ceiling surfaces with integrated KaRo mats are hung like sails under the bare ceiling, in order to cool or heat specific work places. The KaRo sails can be made of plaster board or metal. Their performance per m² of active surface is somewhat higher of that of the standard ceiling, if the gap between the sails and the bare ceiling remains open, because then the top side of the sails can contribute to cooling the room, and an air interchange with the room can take place over the edges of the sails.


Also KaRo metal ceilings have high dynamics because of the thinness of the capillary tubes, which allows the KaRo mats to be imbedded close to the surface of the plaster.


"KaRo cooling can be switched on like a light." This is the feeling you get if you first turn on the KaRo ceiling in the middle of a warm day. After just a few minutes, the KaRo ceiling begins to cool the room effectively. This is brought about by the very small amount of water in the capillary tubes and the positioning of the mats closely to the surface. In addition, the KaRo ceiling is able to regulate itself quite well.


Central Air conditionings like V.A.V or fan coils system are responsible of contamination like SARS or legionella pneumophila.



4) Advantages of KaRo systems ventilation


The only Air conditioning system that stops cross-contamination from Sars is to have 100% fresh air in each room. The combination of KaRo sensible Cooling Ceiling associated with a Dedicated Outdoor Air System with a latent cooling avoid cross contamination of air in the rooms and save energy in at least seven ways.


  1. Separate ducted Fresh air ventilation path to the space assures that the ventilation air gets to the occupied space.

  1. Providing outdoor air directly to the space easily accommodates after hours humidity and temperature control using a two speeds Fresh Air AHU. The tenants are always entering in a fresh dehumidified room.

  1. Because the outdoor air is delivered directly to the space, the terminal cooling mats are not required to operate during unoccupied periods.

  1. The constant volume ventilation can be easily air balanced in the space since the ventilation air is delivered through dedicated diffusers and represent only 1/5 of the AC load.

  1. By decoupling temperature and humidity control, this significantly reduces blower power compared with a standard V.A.V. system. This applies to either chilled water system or a DX (Direct Expansion System)

  1. In Radian Ceiling System water is used to transport the energy instead of air. The volume of water is 1000 time less than the volume of air needed to transport the same energy.

  1. Because the ventilation make-up air is separately conditioned from the internal loads with the entire building humidity load is handled in the process, the radian cooling and heating ceiling will be operated separately to maintain temperature control. This enables the use of higher heat pump water temperature for the ceiling sensible load. Cooling water at 15oC evaporative temperature at 8 to 10oC increasing the COP of the compressor.



5) Description of Installation


One set of KARO active metal cooling ceiling 600 mm x 1200mm covering around 80% of the room office area will be installed in the offices and the corridors will be equipped with around 30% of active ceiling. The patient rooms will be equipped with KaRo mats and plaster or plaster board depending of Architect design.



6) KaRo saving


A general perception exist that replacing one system with two parallel systems, radian ceiling and a Dedicated Outdoor Air System with a latent cooling will cost more.


In facts


ASHRAE Journal 43 "Ceiling Panel Cooling System": List nine categories of building mechanical system and overall building reduced by radian Ceiling and D.O.A.S.


    1. Reduced chiller tonnage.
    2. Reduced chiller capacity.
    3. Reduced condenser water pump capacity.
    4. Reduced ductwork size and cross section.
    5. Smaller air distribution plenums and thermal boxes
    6. Reduce Air handler size.
    7. Reduced electrical service in line with reduced peak chiller, blower and pump power.
    8. Less "rent able" space air consumed by mechanical equipment
    9. Reduced total floor height by a minimum of 50 cm per floor