Most building problems aren't equipment failures. They're information failures.
I'm the office administrator for a 70-person architecture firm. That means I'm not an HVAC technician, but I'm the person who gets called when the break room starts to smell like humid dust, or when the thermostat on the third-floor fan coil starts blinking a code I've never seen. Since I took over purchasing and facilities coordination in 2020, I've processed 60-80 service-related orders per year. And I've developed a strong opinion: too many HVAC service calls happen before anyone reads the equipment's own manual. That wastes money, and it can produce repairs you didn't need.
The SeasonMaker unit that taught me to check the manual
Three years ago, a McQuay SeasonMaker fan coil unit in our east meeting room started making a faint hissing sound. My first thought was, 'call the refrigerant vendor.' My second thought, after I opened the equipment folder, was better. I found the McQuay thermostat manual stuck behind a start-up report from the original installers. The manual included a short fault-code table. The code blinking on the thermostat display corresponded to a bad thermistor sensor.
We called a technician with that code already in hand. He replaced the sensor in about twenty minutes. The trip charge was still on the invoice, but we paid for a specific repair instead of a broad 'compressor and refrigerant' investigation.
What most people don't realize is that a fault code is not a diagnosis. It's a starting point. But it's a much better starting point than having a technician open the unit and start poking around. The manual also contains a maintenance schedule. We now follow it: clean the coils, clean the drain pan, replace the filters.
The 'old McQuay equipment should just be replaced' thinking comes from an era when controls were proprietary and manuals were locked in a file cabinet. That's changed. You can still buy replacement sensors, valves, and fan motors for these units.
Two tools that paid for themselves: a Milwaukee blower and a Dewalt air compressor
About a year later, I made two purchases that looked a little odd on a facilities expense report: a Milwaukee blower and a Dewalt air compressor. Both together cost less than one emergency service call.
We use the Milwaukee blower to blow dust off the fins of the fan coil cabinets and out of the return-air openings. A fan coil unit is basically a small heat exchanger. If you don't brush or blow it at least a couple times a year, it gets an insulating layer of fluff. Then the system works harder and the thermostat never seems to satisfy.
The Dewalt air compressor has an even simpler job. Most 'leaking fan coil' calls are caused by condensate drain lines that are clogged with algae or debris. With a blowgun attachment, we can clear the line in less than a minute. I've never counted how many times we've used it, but it's way more than I expected.
Before you Google 'how to tell if AC compressor is bad'
I understand why people search 'how to tell if AC compressor is bad.' They want a yes/no answer. For a commercial fan coil unit, the signs are usually indirect. You don't have to be an engineer to tell a technician what you're seeing. Here's what I've learned:
- The compressor is running, but the air never gets cold. That usually means low refrigerant or a bad reversing valve, not a dead compressor.
- The compressor clicks on, runs for a few seconds, then resets. That could be a capacitor or a hard-start kit, not a compressor replacement.
- The compressor hums, the thermal overload trips, and the top of the compressor feels hot. That can be an electrical issue or an internal fault.
Honestly, I'm not sure why some compressors run for twenty years and others die young. My best guess is that coil cleanliness and refrigerant charge matter more than the brand. What I'm confident about is this: if you call a vendor and say 'my compressor is bad,' they'll sell you a compressor. If you say 'the compressor is clicking and shutting off; could it be a capacitor?' they'll bring the right parts.
This approach worked for us because we're a single-location professional office with predictable hours. If you're running a hospital, lab, or data center, please ignore most of this and keep a strong 24/7 maintenance contract. Your risk profile is different. I can only speak to my own context.
What I decided after going back and forth
I went back and forth between signing a full preventive-maintenance contract and our current 'manual-plus-in-house-care' model. The contract made sense on paper. My gut said we'd pay for a lot of inspections that were really just 'walk through and look.' What settled it was that the McQuay thermostat manual included a simple schedule: check the filter monthly, clean coils twice a year, keep the drain pan dry. That's not a secret. It's just in the manual.
Maybe you're thinking, 'You're an office administrator, not a technician. What makes you qualified to have an opinion?' Fair. But I'm the person who sees the invoices. I've watched vendors quote thousands of dollars for work that a little information and a $40 part solved. I've also had to explain to my finance team why we paid a diagnostic fee for a part that failed because nobody had read the manual.
Efficiency is not about being cheap. It's about having the right manual, the right tools, and the right threshold for calling in a pro.
The McQuay SeasonMaker fan coil units in our building are not new, but they work when we give them basic attention. The Milwaukee blower and the Dewalt air compressor have already paid for themselves. And the compressor is still cooling, which is more than I can say for my relationships with a couple of service vendors.
Efficiency is a form of respect for other people's time and budget. That's why I believe more maintenance problems should be solved with information first and a service call second.
