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Avoid using air conditioners when possible:
- In most cases, a fan will produce the same comfort feeling as an air
conditioner. They lead to temperature feelings of 3°C to 5°C lower than the actual temperature and have lower electricity consumption (usually
less than 10% of air conditioner consumptions).
- Avoid unnecessary heat flows, such as excessive lighting, too hot equipment etc. Switch off when unused. Pipes and other heating sources should be well insulated so that the surface temperature does not exceed 40°C.
- Eaves and awnings are good tools that avoid the entry of sunrays during the summer.
- Use, when possible, natural ventilation to cool rooms whenever outdoor temperatures and humidity levels drop (usually when ambient temperature is below 23°C).
Use your air conditioner correctly:
- Fix an acceptable level of comfort (about 25°C) and install control devices (thermostats) to regulate the air conditioning system according to the required temperature. With each degree below the comfort temperature, you are wasting 8% more energy.
- Keep doors and windows closed.
- Set your thermostat at 28°C if the room is going to be unoccupied for more than four hours.
- Program your air conditioner so that it turns on 30 minutes before you arrive and turns off 30 minutes before you leave the room.
- Good insulation is very important to avoid cold leaks (follow the same advice
given in the Heating systems section.)
- Make sure the cold flow is well distributed throughout the space, avoiding areas with too cold or too hot air streams (near windows, doors etc). If your air conditioner has adjustable louvers, adjust them towards the ceiling, since cool air falls. Install thermostats in representative areas.
- Make sure supply ducts are sealed, well-insulated and free from obstructions. Otherwise, the efficiency of central air conditioning would drop significantly. Consult your service technician.
Buying a new air conditioning system:
Step 1: Before acquiring an air conditioning system you need to make sure that you really need it. Air conditioners are quite expensive when compared to fans and most importantly, they consume large amounts of electricity. Are you sure you cannot reach a comfort level using an inexpensive fan?
Step 2: If you have finally decided that you need an air
conditioner, choose the type of system that matches your needs. The table
below shows the different air conditioning system options.
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Room Air Conditioners
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Central
Air Conditioners |
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Used to cool single rooms rather than an entire building.They
are less expensive to operate than central units, but their
efficiency is generally lower.
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Central air conditioners use suppy and return ducts distributed
along the building through which the cooled air and the later
warmer air circulates.
Most air conditioners are split systems,
meaning that the coil is located indoors and the condenser,
outdoors. When the coil and the condenser are both located
outdoors in the same unit, the system is called a packaged
system. |
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Heat Pumps
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Evaporative
Coolers |
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A heat pump can serve as a heater and as an air conditioner.
In the winter a heat pump draws heat from the outdoor air
and circulates it through ducts into the building.
During
the summer, it reverses the process and draws heat from
the interior air and releases it outdoors. These systems
can make
significant energy savings working as both, heaters and
air conditioners. |
An evaporative cooler is a completely different type of air
conditioner that works well in hot, dry climates.
These units
cool outdoor air by evaporation and blow it inside the building.
Windows should be opened to allow
warm indoor air to escape as it is replaced by cooled air.
They cost about one-half
as much to install as central air conditioners and use
about 25% as much energy. However, they require more frequent
maintenance
than refrigerated air conditioners and they're suitable
only for areas with low humidity |
Step 3: Size your air conditioner correctly to achieve
the longest run times possible. The efficiency of the typical air conditioner
increases the longer it runs (see
figure 2).
An oversized
air conditioner has shorter running cycles and doesn't take air humidity out.
An undersized one won't be able to keep the rooms cold enough in hot summer
days. Sizing does not depend only on the size of the room, there are other
factors to be taken into account like:
- Local temperature
- Humidity
- Number of windows and doors
- Insulation of ceilings and walls (see Thermal insulation)
- Average occupancy.
Make sure your contractor uses calculation tools when sizing your installation.
Step 4: look carefully at the energy rating of the new
air conditioner. Like other equipment covered by EU energy labels, air conditioners
are graded on a scale from A-G, where A represents the best equipment that is
widely available and G the worst (see
figure 3).
Figure 3: EU energy label of an air conditioner
Equipment with a higher rating may cost a little more initially, but G-rated equipment will use 50% more electricity under normal operating conditions compared to A-rated units. The energy label will also show estimated annual energy consumption in kWh.
Most A-rated air conditioners have low standby power (consuming less than 1 watt).
Step 5: install the system correctly. Poor installation can make an efficient air conditioner perform as an old inefficient one.
Central air conditioning systems:
- Place the condensing unit in a well-ventilated area away from solar radiation.
- Make sure there is enough space for installation and maintenance.
- Avoid installing ducts in attics. The large temperature difference between attics and ducts results in heat conduction, reducing the efficiency of the whole system.
Room air conditioners:
- Place the system in a window or wall area near the centre of the room and on the shadiest side of the house.
- Locate thermostats in representative areas, away from heat sources.
Proper maintenance is very important to obtain the best performance of your equipment:
- Clean and check your air conditioner every 2-3 months. Dirty filters and coils and bent fins can block the normal air flow and impair the heat absorbing capacity of the evaporator, reducing the efficiency of the system. Savings can range between 3 and 10%.
- Your service technician should also check electrical connections and contacts. This is a common source of failure, especially when air conditioners are turned on and off frequently.
- The efficiency of your system will drop significantly when the refrigerant charge does not exactly match with the manufacturer's specifications. Check if your air conditioner has the right refrigerant amount. Consult your service technician if not.
- For large and rather old air conditioners adjust the pressure switch to allow compressor head pressures to vary with outdoor conditions. New air conditioning equipment usually incorporates automatic head pressure controls.
- Ask your technician how you can increase the efficiency of your system when operating at partial load.
New technologies:
- Consider the option of installing an absorption machine. These systems have some common features with air conditioners and heat pumps but differ in some important aspects. Instead of compressing vapour between the evaporator and the condenser, the refrigerant is in this case absorbed by a secondary substance, called an absorbent, to form a liquid solution. The liquid solution is then pumped to the higher pressure. Absorption refrigeration systems have the advantage of relatively small work input compared to vapour-compression systems like air conditioners or heat pumps. These systems are especially advisable when the facility has waste heat. However, natural gas or some other fuel can be burned to provide the heat source.
- Consider trigeneration: the simultaneous production of heat, electricity and
cold with a single prime mover. This option is especially recommended to energy
intensive industries and buildings (see CHP technologies).
- There are innovative systems that can be cost-effective, like the production of ice during off-peak hours and its later use for air conditioning and refrigeration in peak hours. Consult a specialist.
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