Common Issues with Mini-Split Systems and How to Address Them
When Summer arrives and temperatures start to rise, dependable air conditioning can be a life saver. If your mini-split is letting you down, we’re here to walk you through how to address it and the reasons behind it.
Understanding Your Mini-Split
A mini-split is a type of heat pump designed for smaller spaces. It consists of two separate components, an outdoor condenser unit and an indoor air handler, connected by refrigerant lines. Together they work to heat and cool your home.
In cooling mode, your mini-split uses the refrigerant circulating within it to extract heat from your home and release it outdoors. As cold refrigerant flows through the coil within the indoor unit, the fan blows air over it and into your space. This cools the air and warms the refrigerant within the coil. The now warm refrigerant flows to the outdoor unit where it is condensed, releasing the extracted heat as it cools.
Learn more about the great mini-split models Lennox has to offer.
Common Reasons Your Mini-Split Isn’t Cooling and How to Address Them
There are a number of things that can cause mini-split cooling issues. They range from simple fixes that you can take care of on your own to more technical issues that require a technician
Before you incur the cost of calling a professional, we advise you to do a little troubleshooting to see if the issue isn’t a simple fix you can address on your own.
Check for Inadequate or Blocked Air Flow
The most common reason for poor system performance in any HVAC system is poor air flow. In a mini-split system, air flow can be restricted both indoors and outdoors. Indoor air flow can be reduced by dirty equipment and a clogged or out of date filter. When a filter is particularly dirty, these performance issues can be accompanied by a stale musty smell.
Inspect and clean your air handler to remove any dust build up on the vents and panels. Check your filter and clean it if necessary. If it’s extremely dirty or overdue for replacement, you should install a new one as soon as possible. Neglecting manufacturer-recommended filter replacement can cause a variety of issues with your mini-split including: 
-
- Poor cooling and heating
- Water build-up and leakage
- Mold and mildew growth
- Bad odors
- System damage
Air flow can also be blocked outdoors. Make sure there is nothing reducing the free flow of air around the outdoor unit. Debris or objects moved in front of the fan can reduce air flow and cause the condenser coil to preform inefficiently.
Make Sure Your Thermostat is Set Correctly and Working Properly
When using your mini-split for cooling, setting your thermostat too low can overwork your system, causing it to be inefficient. When the thermostat is set more than 4 or 5 degrees below the current indoor temperature, your system will cycle on and off repeatedly, attempting to achieve the desired temperature, working harder while never actually reaching a stable temperature.
Assuming your mini-split is appropriately sized for the space, we recommend reducing the temperature within your space incrementally or if you have a smart thermostat, programming a gradual shift in temperature based on your needs and the weather. This will allow your unit to better keep up with the demands.
If your thermostat is in need of calibration, this can also cause ineffective cooling. If you suspect this may be the case, and depending on the specific thermostat you have, consult your user manual and go through the included calibration procedure.
If you’ve done the troubleshooting we just covered and the issue continues, you likely have a more complex issue – one that requires the assistance of an HVAC professional. Here are a few of the most common problems that will require a visit from a technician.
Low Refrigerant
Refrigerant is what makes heating and cooling possible in all HVAC systems. Without an adequate supply your mini-split will struggle to meet demand. By design, all air conditioners are closed systems, so if your refrigerant is low, you have a leak. Sometimes, when a leak is present, the air coming from you air handler will have a sweet, slightly vinegar smell. If you notice this, turn off your system and call a technician as soon as possible to address the issue and recharge your system. Running your system without adequate refrigerant can cause additional damage – raising repair costs.
Indoor Sensor Fault
Your air handler has built-in sensors that measure the temperature in the room, telling the system when to cycle on and off. A malfunctioning sensor can send incorrect readings, causing your mini-split to shut down prematurely – never reaching your desired temperature.
Malfunctioning Condenser
The condenser is responsible for removing heat from the refrigerant within your system. Without a properly working condenser, your system can’t cool your home. Age, dirt and debris build-up, or weather damage are all possible causes for a faulty condenser.
An air conditioner is a complex machine – even a mini one – and there are a variety of sensors and other vital components within your mini-split that, if malfunctioning can cause poor performance. If your cooling problem is determined to be a mechanical issue, your technician will advise you on the specific problem and how to address it.
What to Expect When You Call a Professional
As we discussed, there are lots of problems that could be preventing your mini-split from cooling effectively. Many of them will require the trained eyes of a professional technician.
If a technician is required, once they arrive, they’ll do a thorough inspection of your system to help them diagnose the issue. They will:
-
- Inspect and clean the indoor and outdoor units.
- Perform operational and diagnostic tests on both.
- Check for refrigerant leaks.
- Inspect all mechanical and electrical components.
Once they’ve finished, unless the issue was something minor that they are able to address during their inspection, they’ll give you their diagnosis, suggest solutions, and go over the costs associated with each option.
It’s important to note that “emergency” calls like these can usually be avoided with regular seasonal maintenance. Engaging a local HVAC pro each Spring and Fall for a system tune-up can help avoid breakdowns and the discomfort of being caught without heating or cooling when you need it most.
Keeping Your Mini-Split Happy and Healthy
Understanding your mini-split, being aware of its performance, and keeping up with routine maintenance can go a long way toward avoiding costly repairs. Keeping your equipment clean and replacing filters according to manufacturer recommendations will not only help reduce the chances of breakdowns, but it will also improve efficiency, help keep your electric bills manageable, and extend the life of your system.
Optimizing your thermostat setting is also a good way to ensure your system isn’t overworked in the heat. Here are a few thermostat tips that will help you get the most out of your mini-split this summer:
-
- Choose temperatures you can be comfortable with without overworking your system.
- Cool your space incrementally avoiding sudden temperature reduction over 4 degrees.
- Select and program appropriate daytime and nighttime temperatures.
- Raise your thermostat’s temperature, reducing system demand, when you’re at work or the space is not in use.
- Use the fan setting to improve air circulation when the unit isn’t actively cooling.
If you’re having performance issues with your mini-split, or just want to schedule that next tune-up, give your local Lennox technician a call and schedule a visit. They’ll ensure your mini-split is performing its best and help you stay on the road to perfect air.
