How to Keep Your Laundromat’s HVAC Units Running as Smoothly and Efficiently as Possible

Hopefully, by now any lingering heat from summer has passed and the cooler weather of fall is upon us. I say “hopefully,” because the summer heat can create a number of challenges for laundromat owners – especially for their HVAC systems.

Despite taking all of the necessary preventive maintenance steps, it seems Murphy’s Law always makes itself known at the most inopportune time, like the hottest days in the middle of August, and one of your HVAC units fails. At least that has been my experience, despite my best intentions to keep my HVAC units running properly.

With all due respect to Mother Nature and Mr. Murphy, there may be more than hot weather and coincidence causing laundromat HVAC systems to fail.

Laundry dryers and water heaters need makeup air to combust, which can compete with HVAC supply and return air. Also, dryers produce a lot of dust, which can collect in both the evaporator coils and condenser coils, causing your HVAC system to run inefficiently and potentially fail due to compressor high head pressure.

In addition, dryers can produce residual heat, especially at the dryer doors, which is in direct conflict of the HVAC system trying to cool the air. Solar gain, such as the orientation of the laundry’s storefront and the number of windows, also can impact how much HVAC capacity is needed for cooling – as well as the number, size and type of doors a laundromat has, which can enable cool air to escape.

Taking all of these variables into consideration, it’s easy to see how an HVAC contractor may need to apply more than a standard approach on how to properly size and maintain a laundromat’s HVAC system. So, let’s explore these laundry-related HVAC issues in more detail (from the perspective of a laundry owner who has learned the hard way from his own mistakes) to help stimulate future discussions with your HVAC contractor.

There are several sources of information on dryer makeup air, including calculations for sizing outside penetrations based on the number and size of dryers. As a result, I will leave that specific topic to the dryer manufacturers. However, it’s easy to see that, if your dryers don’t have enough makeup air, they may compete with your HVAC system and potentially consume air that has already been conditioned.

In addition, depending on the flow of air inside your store, dryers that may consume conditioned air also may affect the static pressure of your HVAC system, thus making it less efficient. Believe it or not, there is a fine balance an HVAC system must maintain between the air flowing into the system and the air flowing out of the system, and dryers competing for that air can disrupt that balance.

What’s more, dryers without ample makeup air may literally suck in warm air through openings like a doorway, which also may affect HVAC efficiency. It’s hard enough to cool an airtight space without introducing warm air leaks into it.

Even if you think you may have enough makeup air for your dryers, I learned from a recent CLA Connect Open Forum post by Alabama multi-store owner Ken Barrett that a great way to confirm that you indeed have adequate dryer makeup air is to turn off your HVAC system, turn on all of your dryers, and then determine if there is any airflow through each exterior door. Hopefully, there’s no airflow and you can confirm that your makeup air is sized properly.

Perhaps the greatest impediment your HVAC system will have is all of the dust produced by your dryers. Both the dust inside your laundromat and the dust coming out of your dryer vents may affect your HVAC system. Inside dust can be sucked into the return air vents, which flows over the HVAC evaporator coil, and outside dust can be sucked into the condenser coils. Eventually, the dust will block airflow over the coils, causing your HVAC unit to work even harder to have the same effect. Typically, HVAC compressors will have higher head pressure if this occurs, which may cause them to temporarily stop working or even fail.

The most obvious way to visually see this problem is to inspect the return air filters inside your laundry or the filters right next to the evaporator coil inside the HVAC unit. If the filters are clogged, you may be literally “starving” your HVAC system of the air it needs to function properly, affecting the static pressure. Outside, you can visually inspect the condensing coils for lint buildup.

A third way to determine if your coils may be clogged is to use an infrared thermometer inside your laundry and “shoot” the temperature at your return air duct and compare it to your supply air ducts. Normally, the temperature difference should be about 15 degrees. If the temperature differential drops to 5 degrees to 10 degrees, your HVAC coils may be clogged and need cleaning.

Besides routinely changing inside return air filters, another potential way to help your HVAC system function smoothly is to consider adding additional return air vents. Doing so may reduce the frequency of having to change filters. Just make sure not to add too much return air capacity to where it affects the static pressure. If possible, you also may want to locate the return air vents away from dryers where they may be less likely to collect lint. Cleaning the evaporator coil at least once a year will help remove any lint that may have gotten past your filters.

Unfortunately, there’s no practical way to filter lint from outside HVAC condenser coils. The most obvious solution to this problem is to try to physically distance the condenser coils from the dryer vents as much as possible. If you have dryer vents penetrating your roof, try to have the HVAC condenser on the ground. Similarly, if you have HVAC units on the roof, try to vent dryers out the side of your building.

If you must have both the dryer vents and HVAC condenser on the roof, try to space them as far apart as possible. Also, make sure the HVAC condenser is not “downwind” from the dryer vents, and position the vent caps to flow away from the HVAC condenser. Similarly, if your HVAC condenser is on the ground, attempt to position it away from the dryer vents.

If physically distancing your dryer vents from the HVAC condenser is not an option, you most likely will need to routinely clean the condenser coils. You can contract out this work, but if you have a garden hose and a little time, you can probably do it yourself.

HVAC condensers on the ground are easier to clean, but if your condenser coils are on the roof, you may want to consider having your plumber put a hose bib up on the roof to make the task easier. I also have found through personal experience that HVAC units with microchannel coils are far easier to clean than those with copper coils with aluminum fins. The microchannel coils withstand the hose water pressure better, making cleaning faster and easier – and most microchannel coils are only one layer thick, eliminating the potential for any lint to buildup between coils if they are more than one layer thick. Most microchannel coils don’t require any chemicals for cleaning, and I’ve found cleaning the condenser coils with a garden hose from the inside out to be most effective.

One final thought on lint clogging coils is the issue of sizing HVAC capacity, which is usually measured in tons. Unless you have the capability of washing your condenser coils daily, there will be a propensity for some dryer lint to accumulate in your condenser coils, and that clogging of the condenser coils is going to affect the capacity utilization of your HVAC unit. In other words, additional HVAC tonnage may be needed to compensate for the time in between coil cleanings.

Intuitively, if your HVAC unit is running at 80 percent of capacity because the condenser coils are partially clogged with dryer lint, one could argue that a 20 percent increase in tonnage may be required. Likewise, if your HVAC capacity is undersized, you may find yourself cleaning the condenser coils far more frequently, not mention all of the additional wear and tear on your condenser fan motors and compressors, which seem to never stop running.

I have firsthand experience with this problem and suspect many other laundry owners have as well, because HVAC contractors may not be factoring lint clogging condenser coils into their load calculations.

Another consideration for sizing laundry HVAC capacity is solar gain, which is dependent on the direction of your storefront, as well as the number of doors and windows. These load calculations are fairly straight forward, but the heat gain from dryer doors is often overlooked. One way to compensate for this heat gain is to treat dryers like windows in load calculations.

How you chose to size and maintain your laundry’s HVAC units ultimately is an extension of how you chose to run your laundry business. Based on personal experience, I believe that many laundry HVAC systems may be undersized, poorly designed or poorly maintained.

However, laundry HVAC systems also can be over-designed, oversized and less energy-efficient. For example, if an HVAC system is oversized, it may cycle on and off continuously, which can wear it out prematurely.

Larger HVAC units may be easier to maintain, but they will be more expensive to purchase and less energy-efficient. Ultimately, the answer will depend on the advice of your HVAC contractor and how you personally choose to run your business.