You can cut up to 30% off the cost of operating your Commercial Air Conditioning System
The Benefits of Pre-Cooling your Air Cooled Air Conditioning Systems
- Increase system cooling capacity
- Reduce power usage (kWh) and cost
- Reduction in power demand (kW)
- Extend compressor life
- Reduce maintenance costs
- Reduce system downtime
- Reduce operating cost by up to 30%
- Requires minimal maintenance
- Easily retrofitted
- Ideal for undersized condensers
- Improved occupant comfort levels
- Gives a fast ROI
Pre-Cooling is vitally important for Commercial HVAC systems to operate efficiently.
Air conditioning (HVAC) systems are always going to struggle when faced with ambient temperatures above their ideal operating range. The Mistafog CoilCool evaporative pre-cooling system is the most effective way of reducing energy and maintenance costs while also increasing the peak cooling capacity of the system.
Many air conditioning systems use air-cooled condenser units to provide the cooling capacity of the system. These systems must expel heat into the surrounding air in order to reduce the temperature and re compress the coolant. The higher the ambient temperature the harder it is for the condenser to expel the heat and the less efficiently the system operates, resulting in higher running costs and lower cooling capacity.
With the air conditioning accounting for between 30% and 60% of the cost of operating a commercial or office building and power prices increasing dramatically over the last 5 years, air conditioning pre-cooling has become an essential addition to the building owners operational plans. An air conditioner running at full capacity for longer, will require much higher servicing costs over its lifetime.
In addition to saving power costs, pre-cooling systems reduce maintenance requirements for air-cooled condensers by reducing running and cycle times in order to produce the same amount of cooling capacity.
Coil cool pre-cooling will ensure that the air conditioning system can operate within its optimal temperature range all year round.
How does evaporative pre-cooling work?
Evaporative pre-cooling or adiabatic pre-cooling is easily installed to new or existing air-cooled condensers. It is custom fabricated and installed in front of the coil faces of the condensers in order to atomise water at high pressure in the incoming airflow. As the water is atomized down to between 5 and 10 microns the fog flash evaporates cooling the air entering the coil unit. The ideal way to operate pre-cooling systems is to evaporate the water in the air in front of the coils and before it goes through the coil unit. This is far more effective then a system commonly used by building owners and air conditioning contractors where a struggling unit is sprayed with water from an irrigation system or garden hose in order to cool the coils. By pre-cooling the air before it enters the coils it gives far more effective cooling as the full air flow is still able to flow over the coil fins whereas wetting the coil fins disrupts the airflow and with far bigger droplets of water needing to be evaporated, is far less effective than evaporating the water in front of the coils.
Unlike most air conditioning systems evaporative pre-cooling becomes more effective the higher the ambient temperature i.e. the higher the temperature the more mist can be evaporated into the air and the bigger the differential between ambient temperature and the temperature of the air entering the coils.
By lowering the workload on the air conditioning system via lower head pressures within the compressor system in the condenser, wear and tear on the overall system is greatly reduced. High head pressures within a system will shorten the life of the compressor whereas lowering the head pressures through evaporative pre-cooling will extend the life of the condenser unit.
Coil cool evaporative cooling has been shown in tests to reduce power use by over 30% in even moderately warm temperatures of around 33 degrees C. In higher temperatures the power savings will be even greater.
What is the return on investment of an air conditioner pre-cooling system?
The most obvious cost that can be calculated in the ROI calculation is power savings made during the late spring, summer and early autumn months. In power costs alone owners of commercial air conditioning systems should see their investment recouped within 2 years although in many cases this can be done in as little as one summer. If an owner is also wetting their coils to help the condenser function during the hotter days, they will also see a significant saving in water. Maintenance costs will also be reduced due to the lower loads being experienced by the condenser however these a much harder to quantify other than on a case by case basis. If the coil units have been hosed to keep them cool, they may experience significant corrosion and early failure which will be avoided through the use of high pressure evaporative cooling.
What is evaporative cooling or evaporative pre-cooling?
Evaporative pre-cooling or adiabatic cooling use the laws of thermodynamics meaning that for water to evaporate heat must be taken from the air to complete the process. The smaller the water droplets the quicker they will evaporate and hence by having water droplets between 5 and 10 microns they are able to flash evaporate removing heat from the air in the process. As this fine fog is being injected into a moving airflow this makes the evaporation process even more efficient dropping the air temperature down into the air conditioning systems ideal operating range. Evaporative cooling has been in use for hundreds of years. We have just used modern high pressure technology to improve the evaporation process through high pressure pumps and atomising nozzles. Unlike irrigation systems there should be no, or very little wetness with high pressure pre-cooling.
How do I know this will save me money?
The graph below shows the official ambient temperature of the air at an installation in Sydney’s western suburbs.
As you can see the ambient air temperature is above 26 degrees for over 9 hours on this particular day, 12th of March 2019, which is far from the height of summer. In this case the temperature of the air entering the coils was measured at the coil face at over 36 degrees at 2 p.m. Measurements of the air temperature across the coil face with the pre-cooling unit running showed 24 degrees, well within the units ideal operating range.
Manufacturers regularly test and publish information on the power usage in cooling output of their systems under various temperature conditions.
This extract from Carrier’s published data shows that this unit will use 50.94% more power in 46 degree ambient temperature to what it would in 24 degrees. 46 degrees is regularly achieved in locations where condensing units tend to be situated such as in plant rooms and on the roofs of buildings.
Is it better to fit an air conditioner pre-cooling system before or after installation of the condenser coil unit?
As the pre-cooling system is being fitted to the outside of the coils in the direct air flow it is better that they’re installed, even on a new system, after the condenser has been installed on site. For this reason, the adiabatic pre-cooling system can be installed just as easily on a new or existing condenser.