The Repair or Replace Decision for Air Handling Units

In the world of commercial and industrial HVAC systems, air handling units (AHUs) are the workhorses – regulating temperature, humidity, and air quality for everything from office buildings to manufacturing plants.

But like any heavy-duty equipment, AHUs don’t last forever. The average lifespan of a well-maintained commercial AHU is 15-25 years, depending on usage, environment, and maintenance history. When performance dips – indicated by temperature swings, rising energy bills, uneven airflow, and/or frequent breakdowns – the big question arises: should I repair/refurbish or replace?

At Marlo Heat Transfer Solutions, we’ve been building custom coils for AHUs since 1925, for a very wide range of industries. We also have a long and successful track record producing air handling units – including our modular, pre-engineered MarloAIR AHU that was introduced in 2018.

So, we know AHUs inside and out. Plus, because we produce coils and removable coil modules (both critical components in refurbishing an AHU) as well as complete air handling units, we can take a neutral position on the decision to repair or replace. Listed below are some critical factors to help you make a smart, cost-effective decision.

1. Age of the AHU

The rule of thumb is, if your unit is under 10-15 years old, repair is often the winner. But if you get to that 15 to 20 year mark, the decision should typically lean toward replacement. Older AHUs most likely have multiple components that are nearly worn out – or completely worn out – like fans, motors, dampers, coils, etc. So, when you make one costly repair now, you might be making another one in the very near future.

2. Energy Efficiency and Operating Costs

It’s just a fact that older AHUs will be less efficient and use more energy than a new model.

That means the repairs needed to keep that old unit on life support aren’t the only cost factors to consider. The ongoing energy costs must also come into the equation. Modern upgrades such as EC fans, heat recovery, low-leakage panels and more can cut energy costs by 20-50% over aging units. As a result, the cost of a new AHU will be offset to some extent by lower energy bills. And with rising energy prices in 2025, payback on a new unit may be faster than you think.

3. Frequency of Breakdowns and Downtime

As everyone knows, downtime kills productivity – especially in industrial/manufacturing environments where every minute of your production process is valuable. So, if you’re not producing while an AHU is down for repair, that repair just got a lot more expensive. Even in basic comfort heating and cooling applications, downtime means uncomfortable and unhappy employees, guests and customers. Of course, every situation is unique, so determining your individual costs for downtime (either in actual dollars or in good will) is necessary in making continual repair decisions.

4. Performance Issues and Indoor Air Quality (IAQ)

It goes without saying that if an older air handling unit can’t maintain the needed temperature, something has to be done, whether that can be a repair or if replacement is required. But AHUs don’t just control air temperature. Consider other factors like inadequate airflow, humidity swings, particulates in the air, and even excessive noise generated by the unit. In a post-Covid world, IAQ standards are often above what older AHU can reach. A new AHU can provide things like better filtration, increased outdoor air intake, UV or other antimicrobial protection options and more. These improvements can sway a borderline AHU repair/replace decision to a new unit.

The Middle Ground: Marlo’s Removable Coil Modules

Marlo offers a unique and powerful third choice between the options of repair and replace. Our Removable Coil Modules (RCMs) can replace the entire coil housing section of an existing air handling unit (including a new coil, of course). Ideal for damaged or rusted through coil sections, an RCM not only offers a custom replacement coil, but a completely new housing that is custom designed to be a precise fit for the existing AHU. Marlo RCMs are AHRI certified and include upgraded components such as new coil supports and a stainless steel drain pan with IAQ slope, for better condensate management and indoor air quality.

RCMs are available for both heating and cooling coils, including steam and water combinations. They are fully customizable, feature galvanized or stainless steel cabinets (with optional painted exterior), single or double wall construction, 1″ or 2″ insulation, and even an optional integrated filter section. The coils are removable from either side of the cabinet, offering the ultimate in flexibility during installation and future maintenance. An RCM can extend AHU life by many years, without the cost of a new unit.

When repair isn’t an option, MarloAIR can be the ideal Replacement AHU

AWhen the decision is made to replace an AHU, Marlo offers an excellent option for applications from 5,000 to 24,000 CFM. Our MarloAIR AHU features a pre-engineered, modular design that can be customized to meet specific needs – without the high price and long lead time that come with a completely custom unit.

The modular design and construction make MarloAIR an ideal replacement AHU. The unit is shipped in sections that fit easily through standard building openings and elevators, which are quickly assembled on site. This is an especially valuable advantage when existing units are in tight spaces, allowing installation with minimal disruptions and downtime. MarloAIR offers a superior wall system designed for energy efficiency, a wide range of high-quality fan and motor choices, and is backed by an unmatched 3-year warranty. For all the reasons why MarloAIR is a great option for a replacement AHU, see our blog article.

Need help with an AHU repair/replace decision?

We’re here to help. If you want to discuss your options, send us an email at [email protected] or complete and submit this form. To locate a local Marlo representative in your area, just search by zip code using our rep locator.