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Oct 13, 2021  Al Chan

Ductless Mini-Split Maintenance Guide

If you’ve invested in a ductless mini-split system in your home or building, you will enjoy multiple conveniences and benefits including but not limited to: flexible zoning, cost effectiveness, and energy efficiency. To ensure you enjoy your mini-split system for years to come, it’s very important to keep it in top working condition with regularly scheduled maintenance.

The Importance of Mini-Split Maintenance

In general, there is more work involved with mini-split maintenance compared to a traditional centralized ducted system. A key difference is that a mini-split system requires more air handlers. Along with the size of the air handlers and the need to disassemble each one, you’ll quickly see that mini-split maintenance can be more challenging. However challenging, properly maintaining your equipment is a requirement to avoid underperformance, poor air quality, and premature failure. A certified HVAC technician is always recommended for this type of service to ensure the best results. In this guide, you’ll find all the steps needed to service a mini-split system.

Key Maintenance Benefits

The old saying, “If it ain’t broke, don’t fix it,” doesn’t apply to ductless systems. Any professional who works with ductless systems regularly has seen issues that could have been easily prevented by following proper maintenance procedures. The key to proper ductless mini-split maintenance is to follow procedures that both improve the equipment condition and test for potential issues while doing no harm to the system or the space surrounding the system. Following the proper maintenance procedure improves:

Energy Efficiency

Clean and well-maintained systems produce more BTUs per input watt. This leads to energy cost savings for the customer on their utility bill. 

Indoor Comfort

On ductless systems, dirt on the coils and blower wheel can quickly lead to poor output, affecting temperature and humidity control. 

Breakdown Prevention

Being able to prevent system failures or defects before they happen is the goal of maintenance. Equally as important as preventing problems within the system is preventing any property damage during maintenance.

System Longevity

Proper maintenance can extend system life by taking a preventative approach to potential system problems.

Indoor Air Quality

Cleaner air handlers lead to cleaner air by removing dirt and microbial growth before it becomes an IAQ issue. 

The goal should be to maintain or improve these outcomes while being aware of any pre-existing conditions BEFORE you begin maintenance when possible. This process of pre-confirmation, detailed cleaning and maintenance, and post-maintenance confirmation ensures that the job is done correctly and there is no harm to the system. 

Mini-Split Maintenance Checklist

Now that we’ve covered the importance of maintenance and some key results from the service, on to the checklist! Again, utilizing a certified technician to perform these tasks is always best to ensure optimum results without compromising your unit. For best results, mini-split systems should undergo routine maintenance twice a year, ideally in the spring and fall.

1. Pre-Confirm Operation

Before you begin routine maintenance, you need to make sure all parts of the system are in good working order. If you find any problems, discuss them with the customer before proceeding with maintenance. Then, decide if repairs need to be completed before you perform maintenance or after. Below you will find a list of necessary tasks during a pre-confirm operation to ensure the system is running smoothly prior to maintenance.

  • Set the system to max cooling or heating 
  • Check that the air handler runs with no abnormal noises 
  • Check discharge air temperature from the air handler 
  • Ensure the condensing unit is running with no unusual noises 
  • “Feel” test the suction line in cooling mode 

2. Protect the Workspace

Because the components of mini-split systems are often in highly visible places, your work area needs to be kept immaculate. Not only will this make cleanup easier for you, but it will also help ensure you don't cause damage to the system you're trying to maintain. 

  • Wear shoe covers 
  • Lay down drop cloths in the work area 
  • Move important or fragile objects away from the work area

3. Visually Inspect the Full System

Thoroughly inspecting the system before you start working on it will provide you with a lot of information about its condition and any parts that may need a closer check. Unusual wear patterns can help you catch issues before they cause a system failure. 

  • Ensure you are familiar with the manufacturer’s cleaning and disassembly instructions 
  • Remove access panels inside and outside as needed for testing and cleaning 
  • Inspect for wire or tubing rubouts 
  • Check electrical connectors 
  • Look for signs of oil on tubing and at refrigerant connections 
  • Inspect for signs of abnormal wear

4. Cleaning

hvac technician removing mini-split air filtersMini-split systems that haven't been cleaned regularly are prone to buildups of dirt and dust as well as the potential for mold. Make sure you protect your health by wearing proper PPE. This is also the time you'll need to be especially conscientious about not spreading contaminants or dirt to other parts of the building you're working in.

  • Wear PPE as needed 
  • Remove and clean the air filters 
  • Clean and sanitize the blower wheel 
  • Clean and sanitize the evaporator coil 
  • Wash the condenser coil 
  • Remove debris from around the condenser base and wash the coil 
  • Clean the drain line and condensate pump (if applicable)  

5. Run Test and Observe

Once you've cleaned the system, check to make sure everything is functioning as it should. It is easy to overlook the heat pump in July, however, it is important to check both systems when applicable.

  • Carefully reassemble the equipment 
  • Leave the bib in place and run the blower to dry 
  • Check for rubbing or unusual noises 
  • Test both modes for operation on heat pump systems 
  • Run the system at full cool if possible 

6. Take Key Measurements

Be thorough and alert when searching for potential issues. Even if everything seems to be working correctly, double-check to be sure. Early warning signs for potential problems are not always obvious, something as small as a key measurement being slightly off can be a red flag and it takes a knowledgeable professional to recognize this.

  • Measure Compressor, Blower and CFM Amps 
  • Check applied voltage 
  • Measure outlet air temperature & delta T 
  • Check suction pressure and superheat at full cooling

A Job Well Done

Once all of the proper maintenance steps are complete, and you have verified that the system is working properly, you’re done! Remember, regular maintenance is essential for mini-split systems to run efficiently and protect indoor air quality. Performing routine mini-split cleaning will keep a ductless unit free from mold and protect internal components from unnecessary wear. When a mini-split is running in peak condition, it can live up to its energy-efficient promise that allows for energy cost savings on future utility bills.



Published by Al Chan October 13, 2021