Our Renew program manager, Kyle Henry, outlines the best practices for preventative maintenance this summer to keep your buildings efficient and comfortable.
 
Check Refrigeration on Units
This is what makes air conditioning possible. There needs to be a specific amount of refrigeration in each HVAC system for it to work properly. It’s also important to check refrigerant levels after everything has been cleaned.
  
Check That Condensers Are Not Clogged
Outdoor environmental dirt and debris are ever constant. Coils may clog from various types of debris, such as cottonwood, dirt, grease, dust, soot, and pollen to name a few.

The condenser coil removes the heat gained from your space to the outdoors. A clogged coil will reduce the heat removal process which will reduce its ability to properly cool your space. It can also cause the coil and line-set to freeze up and the electrical components to over amp. This leads to part failures and the system to shut off or “short cycle” (turning on and off rapidly), which can damage the compressor.  

As part of the condenser coil operation, it is important to validate the proper operation of the condenser fans each quarter. If one or more fans fail to cycle on, even a clean coil will be unable to remove the heat gain in the refrigeration line. 
 
Make Sure Evaporator Coils, Drain Pans, and Condensate Drains are Cleaned
The evaporator coil takes heat from your space and adds it to the refrigeration within your evaporator coil. If this coil is clogged, it reduces this heat transfer and recirculates the heat back to your space.

The evaporator coil has another important function: it removes water from the air to reduce the humidity from the space. This water will condensate onto the fins of the coil and drip down into the drain pan which collects the water and removes it to a roof drain via your condensate trap/drain line. If the condensate trap is not installed correctly, or either the pan or trap are full of debris, they will allow the water to remain in the unit. When this happens, the water will eventually be drawn into the supply air duct causing water damage in severe cases.
 
Clean Outdoor Air and Evaporative Coil Filters / Fan Belt Maintenance
Fan belts (assuming the blower is not direct drive) and evaporator disposable filters should be replaced on a scheduled interval. Typical filter replacement should occur each quarter. A minimum MERV 8 filter is recommended. Belt replacement will vary based on the fan type. Most grease fans require belt replacement every 3 to 6 months, whereas most rooftop equipment can be replaced every 6 to 9 months. Your PM team should be able to show you the signs of wear on your belts and recommend the correct replacement cycle.

One often overlooked component is the metal mesh outdoor air filter. This filters the debris from outside before it enters your unit. It requires cleaning every quarter. These mesh filters need to be replaced over time since cleaning will eventually begin to cause them to deteriorate. Normal life for these filters is approximately 2 years and are inexpensive to replace. 

Make Sure the MUA Conditioning Works (If It’s Conditioned)
Many MUA units don’t have air conditioning, but some do. There are different kinds of cooling as well (DX cooling, chilled water cooling, or evaporator cooling). Make sure the MUA is operational, and the blower is running for the fan. If it has air conditioning, there will be a specific compartment for this (just as there is one for the heating element) where you can check that the heating is working. You can test that the cooling is working by taking temperature drops at the supply and return. The equipment should have specifications for temperature drops. You can compare your reading to that number to confirm the cooling is working correctly.
 
Confirm That Economizers Are Working Properly (Outside Air Intake)
Commercial RTUs have an outside or fresh air intake. This is where the economizers are located and how the outside air gets in or is blocked out. We need to make sure economizers are functioning properly, closing, and opening when they should. It’s important that the economizers and the makeup air section are clean.

Outside air helps improve indoor air quality by diluting contaminants present in the air, regulating building pressure, temperature, and humidity levels, providing fresh air for occupants to breathe, and reducing odors.
 
The importance of outdoor air is vast and not easily summarized. For this article, some highlights of not maintaining outside air will cause occupant discomfort, negative building pressures, and is often the cause of mold growth in and around the building envelope. These consequences are usually an indicator that the outside air intake is not working or being closed to assist the coil with cooling. Outdoor air, if properly set and maintained, will not negatively affect cooling. When you have a discharge cooling issue, it is normally related to one of the previous topics discussed in this article.  

Monitor Your Equipment
Setting your equipment up with a monitor helps predict and prevent possible failures, as well as understand trends and where issues might lie. National TAB Intelligence's M3 monitoring solution is agnostic to any manufacturer's equipment and provides real-time updates on your equipment performance. The M3 will provide key metrics to indicate to you when any of the above conditions are out of tolerance, if you have any component or thermostat sequence of operation failure, and we can even tell you if your RTU airflow balance point is out of design. M3 can provide important feedback on usage, run time, and cycling to help you make decisions on how to best operate the equipment to provide instant savings in energy and efficiency. M3 delivers proof, not promises! 

Still experiencing issues after following these steps? It's time for the Revive program - we'll come out and do a full evaluation.