Air Conditioning

Essential HVAC Guide – Air Conditioning Control Systems

Essential HVAC Guide - Air Conditioning Control Systems

People often talk about getting some form of temperature control included with their reverse cycle ducted air conditioning system. So what are the different forms of air conditioning temperature control and how do they work? We will look at the common types of air conditioning temperature control systems and how they work below.

Basic Air Conditioning Controller

The basic controller that comes with your reverse cycle air conditioning system comes with a thermostat that reads the air conditioners temperature. Usually this temperature is read either from the controller itself or more commonly inside the return air box of the unit that sits inside the roof space.

If the temperature is read inside the return air box, it is sometimes not an accurate representation of the temperature in the room. The room itself may be quite cold but by the time the air is recirculated to the return air box it may have warmed up significantly which means the air conditioner will keep running (e.g. the controller in the living room is set to 22 degrees but once the air reaches the return air box it has heated back up to 30 degrees, which in turn causes the air conditioner to keep running).

In this situation, the unit will keep running even though people are becoming cold. There are however two options to counteract this. Firstly, increasing the temperature of the controls will cause the unit to cycle off quicker. It needs to be remembered that the temperature set on the controller is usually not accurate, instead it works as a scale (i.e. if you set to 22 degrees, it does not necessarily mean the room will cool to 22 degrees).

Secondly, some people put a ducted fixed constant in their hallway near the return air grille. This constant as it name suggests is always on. This allows the conditioned air to return easily back up to the return air box of the unit, which helps the unit cycle off. In this instance if you were running just your bedrooms that were all a long way from the return air, the air from the rooms would heat up too much before getting back to the return air. The fixed constant however would bleed air directly back into the grille which will make the unit cycle off and ultimately save you money in running costs.

VAV Air Conditioning Controller

VAV stands for Variable Air Volume system. This is where the zone motors for your reverse cycle ducted air conditioning system allow some temperature control to the rooms you are in.

A zone is basically a series of blades that close the ductwork if you want to stop the air to a room. For instance, if you turn off your bedroom, the blades close restricting the air flow from proceeding down the ductwork and into your bedroom. Likewise, when you want air, the blades fully open and air starts to flow out the diffuser and into your room.

VAV systems work differently however. Instead of the blades simply opening or closing, they can constantly adjust what percentage they are open. This constant adjustment lets you control the amount of airflow you get into a room which ultimately controls the temperature of the room.

For example, if your room is around 30 degrees and you set your VAV controller (located in the actual room) to 22 degrees, the air would rush in trying to cool the room. Once the temperature in the room got to around 22 degrees, the blades will start to close to restrict the airflow to maintain that temperature. As soon as the room temperature starts to increase above 22 degrees, the blades will open again to let more airflow in to bring it back to the 22 degrees. By doing this the VAV system can maintain the temperature in a room.

The VAV system is one of the most basic forms of air conditioning temperature control. It is a cheap way to add temperature control to just a few rooms (say your master bedroom, office and living room for instance).

This system is not to be confused with VRV. VRV air conditioning systems use multiple wall splits (head units) running of a single large outdoor compressor.

Full Air Conditioning Temperature Control

Fully ducted temperature control works the same way as the VAV system outlined above. A controller is located in each room and the temperature is read, whereby the blades open or close to allow the correct airflow to heat or cool the room.

The difference between full temperature control is obviously that the whole house is run by temperature control instead of just a few rooms. Because of this, the full temperature controlled air conditioning system will give you the most comfort as individuals would be able to set their own desired temperatures in their own living areas.

These temperature controlled air conditioning systems are also more economical and cheaper to run than standard systems due to the energy savings they have. This is because once the rooms reach temperature, they can easily switch off which allows the unit to cycle off which ultimately saves the owner in running costs.

Why Choose A Temperature Control Air Conditioning System?

Air conditioning temperature control basically allows each user to set their desired temperature. People are all different and often want different temperatures in their living environment. There our other factors also help determine the temperature a room needs to be such as heat load from devices and people, what clothes the individual is wearing and what side of the house the sun is on. Temperature control systems however overcome these problems by giving each individual control over their own environment.

One thing however these systems can’t do is perform separate cooling/heating operations. If the air conditioning unit is set to cooling, it can only cool rooms. If someone wants heating in one room and someone else wants cooling in another room the air conditioner will not be able to produce this.

I hope this answers some of your questions in regards to temperature control systems in reverse cycle (refrigerative) air conditioning systems. For more advice, speak to the manufacturer and ask as many questions as you can.

James Fletcher has had many years experience in the air conditioning industry. For more air conditioning tips and advice please visit our site. Please visit us for more advice and help on heating & air conditioning, air conditioning brands and much more.

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