EXPOSE AU CONVEGNO EUROPEO POLITECNICO MILANO

CONDENSATION WATER IN AIR CONDITIONERS
PROBLEMS AND SOLUTIONS

By Antoine CHAUVIN, Sauermann Industrie, France

INTRODUCTION

During the past 2 decades, the growth of the exigency of comfort and wellness imposed installation of air-conditioners in most of public and private buildings.

But this generalisation of this kind of equipment exposed people to new sanitary problems. They are partly due to condensation water produced during cold cycles.

1. Formation of condensation water

Many people complain that Air-conditioning dries the atmosphere of the room. This phenomenon is due to the condensation of the humidity of the air, when it passes on the cold battery of the air-conditioner.

The water molecules in gas estate in the ambient air, melt together on the metallic surface of the battery, because of the coldness. They turn them to liquid water. This water condensed (that we call condensates), drip from the battery to a drain pan.

The quantity of water collected depends of many parameters :

. capacity of the equipment
. humidity rate in the air
. flow of the air
. Temperature on the battery

For example, we estimate that a 1 kW equipment produces a maximum of 0,5 litres of condensates per hour in Western Europe climates. This quantity of water, even if it is small, has to be removed from the air-conditioners.

2. Problems and risks linked to condensates

This water cannot always be totally removed from the air-conditioner. The problem is that it contains bacteria and germs. They are brought by two communication mediums :

a) ambient air

For example, the breath of a disease person can send bacteria into condensate water. When the equipment is stopped, the temperature rises and bacteria can develop in this stagnant water. When it starts again, it spreads these bacteria in all the room.

Very famous cases, as " Legionella ", even caused death of few people in USA. But on the side of this very well-know case, many people are affected by respiratory diseases and illness due to air-conditioning.

b) waste water tubing

In some equipment, the depression created by the blower can suck air from the waste water pipe. As this pipe is full of germs and bacteria, this can bring them into the equipment and pollute air and water. The solution would be to install a non-return system between waste water tubing and the drain pan. In most cases, this is not done.

Consequently, in order to prevent one of the main drawbacks of air-conditioning, it should be necessary to develop stronger norms and rules in this domain.

3. Solutions for safe condensates removal

Due to sanitary problems caused by this water, the installer must find a safe technical solution to remove condensates. And for each installation is a different solution.

Few possibilities exist to solve this technical problem :

a) Tubing : water is removed by gravity through constantly declining tubing. This solution is the most commonly used. The main problems of tubing is that it can be unesthetic, and that it does not assure safe separation between air-conditioner and waste water outlet (possible source of bacteria contamination).

b) Evaporation by heating : this solution is mainly used in refrigeration applications. The two main problems are that evaporation by heating does not remove water, but evaporate it (and its bacteria) in the air that can go on the food. The second point is that it is very power consuming (500 W during very long periods).

c) Water pumps : The condensates pumps is the most reliable and adapted solution to remove condensate water with the greater security.

1. The first advantage is that it enables to suck water from the drain pan and remove it in a very high and distant location. Then, it enables to hide tubing from sight.
2. Secondly, non-return valves enable a real separation with waste water.
3. Thirdly, they are equipped with water detection system. The pump is actuated only when water is detected.
4. Finally, they are equipped with safety relay that enables to cut production of condensates in case of risk of overflow of the drain pan.

All these points make pumps the most reliable and safe solution to remove condensates. Three kind are used for this application :
- centrifugal pumps : high flow rate, low discharge head, high life time
- piston pumps : very compact, suction capacity, high discharge head
- peristaltic pumps : low flow rate, low life time

Main characteristics of these pumps are the following :
- reliability
- low sound level (< 32 dBA)
- simplicity and facility of installation
- low power consumption

CONCLUSION

In conclusion, condensates removal pumps importantly improved removal of condensates in air-conditioning and refrigeration equipment. For its sanitary and security advantages, this great innovation will be more and more used by installers as well as directly provided by manufacturers of air-conditioners.