Is It Normal for a Central Air Conditioner to Run Constantly?

July 19, 2017


Some increase in activity is not surprising during the summer months. However, in some cases constant running could be a cause for concern.

close up of external air conditioner

A central air conditioning system that runs constantly can be cause for concern. It’s important to determine whether this is a normal occurrence or if there is a problem with the system.

Some increase in activity is not surprising during the summer months. The air temperature is hotter outside and so the system needs to work harder in order to get the air to the desired temperature. In that respect, it is normal for the air conditioning system to run with fewer on/off cycles. In fact, smaller cycles can be advantageous. It’s good for dehumidifying the home and it can help increase the life span of your system as there is less stopping and starting.

If the home is achieving the correct temperature and the occupants feel it is comfortable, and the bills are at a similar level to previous years, then there is likely no cause for concern.

However, if the temperature is not desirable, if the AC unit literally never stops running and the thermostat never reaches the set temperature, then this is a sign that something is amiss.

What could be the problem?

An undersized air conditioner

A system that is not sufficiently sized for the home could cause this problem. If the system is newly fitted, chances are that it is undersized. In these circumstances, the temperature may never reach the desired level on hotter days. The evaporator coils may freeze but air from the vents will still feel cool and will be flowing normally. This is actually a potentially dangerous situation as the compressor can become flooded with liquid refrigerant. If the compressor becomes damaged, this could be a costly repair. An experienced St Louis HVAC technician will be able to assess a property and determine whether or not the unit is of correct size for the building.

Restricted flow of air

Some indicators of this are: Weak airflow from the vents, although air is cool, a dirty air filter, a blocked vent, the wrong size of ducting or ducting that has been damaged, a faulty blower unit or a frozen evaporator coil. Many of these issues can be easily checked, the air filter can be changed, vents can be checked for blockages, and ductwork can be examined for damage.

Low levels of refrigerant

If refrigerant levels are low, the air will not feel cool from the vents. The evaporator coil may freeze and there may be an obvious point in the system where a leak can be identified. It’s important that your St Louis HVAC technician identifies and fixes any leaks before refilling the system.

Dirty condenser or evaporator coils

This will generally be obvious by looking at the coils. The dirt stops the air from moving in and out of the coils effectively. With the unit trying constantly to get air in and out of the system but failing, this will cause it to keep constantly trying and so it will run all the time without cutting out.

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