Air Conditioning Vents

 Is closing air-conditioning vents a cost-cutting measure?

The air conditioner and the furnace are the main power hogs that consume the lion share of the power that reaches your house from the grid. Under such circumstances, users try their best to save energy as much as possible while using HVACs. Most users have the notion that closing vents in used rooms can save lot of money on power consumption. Let’s see if such a presumption is correct or wrong. A dusted HVAC system has two kinds of grilles- the supply grilles and the return grilles. Through the return side, the hot air from the room is blown into the ducts with the help of a blower. This air is cooled and propelled back into the room through the supply grilles. The return grilles are plain in design. But the supply grilles have louvers just behind the vents, to adjust the flow of air. Being adjustable, many people think that it should be okay to open or close it to suit your needs.

 The blower that plays a central role in moving air into the cooling unit and back to the rooms are powered by an electronically com mutated motor (ECM), which can adjust its speed to varying conditions. However, ECMs are used in upscale devices. Most blowers are powered by permanent split capacitor (PSC). This is not a variable speed motor. The blown air from the room crosses a filter layer that cleans it of aerial contaminants. If the filters get laden with dirt or the design of supply duct does not allow a good airflow, the blower pushes against a higher pressure. In case of ECMs, this mounting pressure causes the motor to ramp up in an attempt to maintain proper airflow. This leads to increased power consumption. The PSC motor will rotate at lesser speed due to the pressure. Remember, this pressure is not healthy on the part of the device.

 Closed vents can increase pressure

The manufacturer of HVAC systems specifies pressure level against which the blower can safely push the air. The pressure limit should not be crossed for the safety of the system. This limit on an average is 0.5 iwc for most systems. The ideal system also has no duct leakage.

However, these are in ideal cases. Practically, most blowers push against a static pressure of about 0.8 iwc. On top of it, if you close your vents the ducts become all the more restrictive for the air to flow. Consequently the motor will ramp up to deliver a good airflow. High pressure in the duct system will result in leaky ducts.

 Closed vents can lead to icy evaporator coil

The air that is blown inside the AC unit from the room is passed over the evaporator coil to cool or heat the air. In most systems the amount of heat the evaporator is capable of absorbing is fixed. As a result when the airflow goes less, a marginal quantity of air reaches the coils. The small quantity of air is not able to dump enough heat in the coils. As a result the temperature of the AC goes down. If the air that passes over the cold coils has enough moisture in it,then the condensation on the coil may start freezing. As a result you will have ice on the coil which is really bad.

 Closed vents can led to faulty compressor

Poor evaporation of refrigerant due to marginal airflow can lead to defective compressors as well. As the entire refrigerant will not evaporate due to low dumping of heat at the cooling coils, liquid refrigerant makes its way back to the compressor. You can rest assured that if the machine continues to function in this condition; the compressor will be dead before long.

The same thing would happen in winter if you have a heat pump. You evaporator would get really hot and therefore refrigerant pressure will shoot tremendously high. This will lead to a burnt compressor or produce refrigerant leakage.

 Carbon monoxide Leakage

Similarly, low airflow in a furnace can get the heat exchanged hot enough to cause cracks. These cracks, then allow exhaust gases to mix with your conditioned air. When that happens, your duct system could be sending carbon monoxide into your home.

 Besides this you will experience a low level of comfort due to bad airflow. You may encounter problems of mold growth in your living space due to lower surface temperatures in winter.

If you are still wondering whether you should close vents to save on energy the answer is a big NO. You will not save any energy by closing your vents. On the other hand high pressure will lead to your blower motor working hard to keep the airflow. This will increase power consumption. Open vents help streamline airflow and allow the unit to efficiently cool your home.

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