I manage the facilities budget for a mid-sized office complex. That means I'm the guy who signs off on the 16x20x1 air filters, listens to the thermostat complaints, and reconciles the quarterly HVAC service invoices. For years, I treated filter changes as a minor line item—something to optimize. I assumed that pushing the replacement cycle from 90 days to 120 days was smart cost control.
I was wrong.
Here's the thing: that decision ended up costing us more in energy bills and equipment wear than it ever saved in filter purchases. Let me explain why, and what I learned about keeping a McQuay Seasonmaker fan coil unit (or any fan coil, really) running efficiently without breaking the bank.
The Surface Problem: What You Think You're Saving
It looks straightforward. A standard 16x20x1 air filter costs around $3 to $7 each. If you have 50 units in a building and change them quarterly, that's roughly $600 to $1,400 a year in filters alone. If you stretch that to every five months, you save maybe $200 to $300 annually. On a spreadsheet, that's a win.
The problem is that spreadsheet is lying to you.
The Deep Root Cause: It's Not About The Filter
The real issue isn't the filter price—it's the static pressure on your HVAC system. A dirty filter restricts airflow. Your fan coil unit has to work harder to push air through. That's basic physics, not advanced engineering.
Why this matters for your McQuay or any brand: When the airflow is restricted, the system's performance degrades in two expensive ways:
- Ice-up risk: Evaporator coils (the cold ones) can't get enough warm air across them. Moisture freezes on the coil. Airflow drops further. It's a vicious cycle that can lead to compressor damage.
- Short cycling: The unit can't reach the thermostat setpoint as easily. It runs longer, cycles more often, and wears out the motor and controls faster.
I only believed this after ignoring it. In my second year, I was chasing a 'saving' of two months per filter change. No big deal, right? Wrong. The result was a $4,200 service call for a blower motor failure on one of our main units. The diagnosis? The motor overheated from running against too much resistance. The cause? A dirty filter that had been running for six months. The cost of that motor replacement was more than my entire annual filter budget.
They warned me about this in the technical manual. I didn't listen. The 'cheap' schedule ended up costing 30% more per year in maintenance.
The Hidden Cost of Neglect
To really understand this, you have to look at the Total Cost of Ownership (TCO). Here's what I tracked after switching back to a 90-day schedule for our McQuay fan coil units and air handlers:
- Energy consumption: Our utility bills dropped by roughly 6-8% in the cooling season compared to the previous year. Dirty filters force fans to run faster—more amps, more wattage.
- Service call frequency: Calls for low airflow or freezing issues dropped by nearly 40%.
- Miscellaneous: Less strain on the thermostat sensors, fewer complaints about temperature swings in the affected zones.
The net annual impact? We saved about $2,800 in energy and avoided roughly $3,000 in potential repair costs. The extra spent on filters? About $150. That's a 20x return on investment. Not bad for something as simple as a 16x20x1 rectangle of fiberglass.
A Note on Thermostat Performance
A neglected filter can also mess with your thermostat's ability to read the room. When airflow is choked, the temperature at the thermostat (which is usually in a return air path or a hallway) doesn't represent the actual zone conditions. The system runs to satisfy a false reading. That 'it's never cool enough' complaint? Often a filter issue, not a thermostat issue.
The Simple, Cost-Effective Fix
I'm not saying you should ignore cost control—that would be hypocritical. But the cost control is in the system, not the part price.
Here's what I do now, and it's simple:
- Set a strict calendar reminder. Every 90 days (or every 60 days in high-dust seasons), I change the filters. Non-negotiable.
- Buy in bulk. I buy a year's supply of 16x20x1 filters from a wholesale vendor in one order. That drops the per-unit cost below $4. It's an upfront cost, but it saves on delivery fees.
- Use the right filter spec. I used to buy the cheapest MERV 4 filter. I now use MERV 8 for critical zones. Better filtration, less dust on the coils, and still low pressure drop. The price difference is a few cents per filter.
- Audit quarterly. I walk the mechanical room with a flashlight. Look at the filter gauge if there is one. Feel the airflow at the supply vents. Visual inspection costs nothing except 15 minutes of my time.
The 12-point checklist I created after my third mistake has saved us an estimated $8,000 in potential rework. It includes verifying filter condition before the cooling season starts.
The Bottom Line
Is the premium filter option worth it? Mostly, yes. A better filter (MERV 8 vs. MERV 4) costs maybe a dollar more but protects your coil. The labor cost of changing a filter is the same either way. You're paying for the service call, not the cardboard box.
If you are managing a building with McQuay equipment—Seasonmakers, chillers, or heat pumps—the principle is the same. The brand is reliable, but no piece of equipment can overcome a dirty filter. I learned that lesson the hard way when my 'optimization' backfired.
Five minutes of checking a filter beats five days of dealing with a frozen coil. Believe me.
