Tip & How-To about Heating & Cooling

Heat Air Exchanger for Heat Recovery

An air-to-air exchanger is used to recover heating or cooling and to improve the air quality of the building that it serves. Typically an air exchanger has two fans, one blowing air into the house and one blowing air out of the house. In the winter time the one fan brings the outdoor cool air through the core warming it with the warm stale air you are exhausting. In the summer time the warm air from the outside will be cooled as it enters through the core to save on your cooling.

Air exchangers often are used to perform many functions such as reducing air contamination, heating or cooling air entering the building, and humidifying or dehumidifying air before it enters the building. Air to air heat exchangers or heat recovery ventilators, are used to provide a balanced flow of air into and out of a building. Ultimately an air exchangers main function is to switch the stale inside air with fresh outside air while exchanging the heat or cool in the process.

There is some controversy about the savings of exchangers. Not only does it require electricity to run the air exchanger, but the air the exchanger brings into your house must be brought up to temperature. This may require that more electric is used to cool your building or that more fuel is also required for heating.

The amount of air that these air exchangers bring into a home may vary depending on how the system has been installed. The codes in many places require a minimum amount of air to be exchanged. Check with your codes official to see what the requirements are for you.

Air exchangers can be a very good thing for many buildings. Especially those that are very large and typically have a lot of occupants with little natural air exchange from doors or windows being opened. However they are also a health hazard if they are not serviced

All air heat exchangers will require regular maintenance. The problem is that this is almost never performed by homeowners, and unless they know about the exchanger it is often overlooked by contractors during service calls. The real problem is that clogged, air-to-air exchangers can make the indoor air significantly worse than it would be without the system installed at all. If you have a home that already has a heat air exchanger, make sure that you keep it very well maintained or disconnect it.

Many air exchangers are controlled simply by on and off switches, but in some applications where the removal of humidity is required, then a humidistat can be used to turn the machine on and off to achieve the humidity level that you want. In cases where there may be a lot of humidity the air exchanger may not be enough to solve the problem. Other devices may be needed to lower the humidity to the level that you want.


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2 Answers

Getting electricity to the fridge but wont get cold.


A likely cause is loss of refrigerant. The compressor will run, but no heat exchange will occur. This requires professional repair, and they have to find the leak, otherwise the problem will recur.
Another cause could be wrong setting of the refrigerator thermostat. Probably less likely, unless someone fiddled with it.
Another cause could be a build up of dust on the heat exchange coils. A refrigerator is a heat pump that removes heat from inside the refrigerator, and radiates it via the coils - usually behind or under the refrigerator. But you'd have to have an awful lot of dust insulating these coils for the refrigerator not to work at all.

Apr 02, 2016 | Refrigerators

1 Answer

on a water cooled scotsman ice machine, should the water be running out of drain line contiuously as its making ice? be cause it just runs all the damn time and thats a huge water bill ...


On a water-cooled system, by design the heat from the machine is being transferred to running water that carries the heat away. Some installations pump this "waste" water to a heat-exchanger or cooling tower (typically on a rooftop), where the heat is transferred again, this time to the air. The water with the heat removed is then recycled back to the machine, where the process is repeated continuously. There is thus no "wasted" water.
If your cooling water is just running down the drain, that's a terrible waste of water and money. Try to find a way of recycling the water by removing the heat and re-using it. Think of ways to use the "free" heat in the water.
Alternatively, buy a proper rooftop heat exchanger and pump the water through it, or, get an old car radiator or air conditioning condenser and a decent blower, and make your own.
Remember that your machine needs constant cool water in order to avoid overheating the system.

Oct 31, 2013 | Kitchen Appliances - Others

1 Answer

Toyota Corolla 1995. Quality of air conditioner reduced when stopped (traffic light) or moving at slow speed (condenced city traffic) No problem on the highway. Checked freon gas and fan. Understand that this model does not have an air cabin filter. What am I missing?


Normal, the ac heat exchanger condenser need air moving across the fins to remove the heat. While moving in town the condenser isn't remove the meat that is building up the it's aluminum fins. Even though the vehicle uses an electric fan. The fan is used to cool the engine temperature. If you Toyota is equip-ed with automatic transmission. The electric fan will need to pull enough air to cool the engine temperature, automatic transmission fluid, air conditioner condenser, and maybe power steering condenser to cool the power steering fluid. Later model of vehicles/trucks are using different refrigerants instead R134A in which you Toyota uses.

The simples way to explain is the ac remove heat from inside your Toyota and this heat is removed by the refrigerants inside your ac in the car. To cool the refrigerant this coolant is removed to the heat exchanger condenser located in front of the engine radiator. So, while moving at 60mph there is enough air flow through the radiator, ac head condenser, and other aluminum heat exchangers. GB...stewbison

Sep 12, 2011 | 1995 Toyota Corolla

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